1
|
Intra- and Intermolecular Charge-Transfer Dynamics of Carbene-Metal-Amide Photosensitizers. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:6621-6635. [PMID: 38690534 PMCID: PMC11056983 DOI: 10.1021/acs.jpcc.4c01994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 04/01/2024] [Accepted: 04/02/2024] [Indexed: 05/02/2024]
Abstract
A series of steady-state and time-resolved spectroscopies were performed on a set of eight carbene-metal-amide (cMa) complexes, where M = Cu and Au, that have been used as photosensitizers for photosensitized electrocatalytic reactions. Using ps-to-ns and ns-to-ms transient absorption spectroscopies (psTA and nsTA, respectively), the excited-state kinetics from light absorption, intersystem crossing (ISC), and eventually intermolecular charge transfer were thoroughly characterized. Using time-correlated single photon counting (TCSPC) and psTA with a thermally activated delayed fluorescence (TADF) model, the variation in intersystem crossing (ISC), (S1 → T1) rates (∼3-120 × 109 s-1), and ΔEST values (73-115 meV) for these compounds were fully characterized, reflecting systematic changes to the carbene, carbazole, and metal. The psTA additionally revealed an early time relaxation (rate ∼0.2-0.8 × 1012 s-1) attributed to solvent relaxation and vibrational cooling. The nsTA experiments for a gold-based cMa complex demonstrated efficient intermolecular charge transfer from the excited cMa to an electron acceptor. Pulse radiolysis and bulk electrolysis experiments allowed us to identify the character of the transient excited states as ligand-ligand charge transfer as well as the spectroscopic signature of oxidized and reduced forms of the cMa photosensitizer.
Collapse
|
2
|
Two-Coordinate Thermally Activated Delayed Fluorescence Coinage Metal Complexes: Molecular Design, Photophysical Characters, and Device Application. Chem Rev 2024; 124:4332-4392. [PMID: 38546341 DOI: 10.1021/acs.chemrev.3c00761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Since the emergence of the first green light emission from a fluorescent thin-film organic light emitting diode (OLED) in the mid-1980s, a global consumer market for OLED displays has flourished over the past few decades. This growth can primarily be attributed to the development of noble metal phosphorescent emitters that facilitated remarkable gains in electrical conversion efficiency, a broadened color gamut, and vibrant image quality for OLED displays. Despite these achievements, the limited abundance of noble metals in the Earth's crust has spurred ongoing efforts to discover cost-effective electroluminescent materials. One particularly promising avenue is the exploration of thermally activated delayed fluorescence (TADF), a mechanism with the potential to fully harness excitons in OLEDs. Recently, investigations have unveiled TADF in a series of two-coordinate coinage metal (Cu, Ag, and Au) complexes. These organometallic TADF materials exhibit distinctive behavior in comparison to their organic counterparts. They offer benefits such as tunable emissive colors, short TADF emission lifetimes, high luminescent quantum yields, and reasonable stability. Impressively, both vacuum-deposited and solution-processed OLEDs incorporating these materials have achieved outstanding performance. This review encompasses various facets on two-coordinate TADF coinage metal complexes, including molecular design, photophysical characterizations, elucidation of structure-property relationships, and OLED applications.
Collapse
|
3
|
Luminescent Bimetallic Two-Coordinate Gold(I) Complexes Utilizing Janus Carbenes. J Am Chem Soc 2023; 145:20097-20108. [PMID: 37642694 DOI: 10.1021/jacs.3c07743] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
A series of bimetallic carbene-metal-amide (cMa) complexes have been prepared with bridging biscarbene ligands to serve as a model for the design of luminescent materials with large oscillator strengths and small energy differences between the singlet and triplet states (ΔEST). The complexes have a general structure (R2N)Au(:carbene─carbene:)Au(NR2). The bimetallic complexes show solvation-dependent absorption and emission that is analyzed in detail. It is found that the molar absorptivity of the bimetallic complexes is correlated with the energy barrier to rotation of the metal-ligand bond. The bimetallic cMa complexes also exhibit short emission lifetimes (τ = 200-300 ns) with high photoluminescence efficiencies (ΦPL > 95%). The radiative rates of bimetallic cMa complexes are 3-4 times faster than that of the corresponding monometallic complexes. Analysis of temperature-dependent luminescence data indicates that the lifetime for the singlet state (τS1) of bimetallic cMa complexes is near 12 ns with a ΔEST of 40-50 meV. The presented compounds provide a general design for cMa complexes to achieve small values for ΔEST while retaining high radiative rates. Solution-processed organic light-emitting devices (OLEDs) made using two of the complexes as luminescent dopants show high efficiency and low roll-off at high luminance.
Collapse
|
4
|
Temperature dependence of radiative and non-radiative decay in the luminescence of one-dimensional pyridinium lead halide hybrids. Phys Chem Chem Phys 2023; 25:21993-22001. [PMID: 37555234 DOI: 10.1039/d3cp02186f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
The photoluminescence properties of organic-inorganic pyridinium lead bromide [(pyH)PbBr3] and iodide [(pyH)PbI3] compounds were investigated as a function of temperature. The inorganic substructure consists of face-sharing chains of PbX6 octahedra. Diffuse reflectance spectra of the compounds show low energy absorption features consistent with charge transfer transitions from the PbX3 chains to the pyridinium cations. Both compounds display extremely weak luminescence at room temperature that becomes strongly enhanced upon cooling to 77 K. Broad, featureless low energy emission (λem > 600 nm) in both compounds have large Stokes shifts [1.1 eV for (pyH)PbBr3 and 0.46 eV for (pyH)PbI3] and are assigned to transitions from self-trapped excitons on the inorganic chains whereas emission at higher energy in (pyH)PbBr3 (λem = 450 nm) is assigned to luminescence from a free exciton state. Analysis of data from temperature-dependent luminescence intensity measurements gives activation energies (Ea) for non-radiative decay of the self-trapped excitons in (pyH)PbBr3 and (pyH)PbI3, (Ea = 0.077 eV and 0.103 eV, respectively) and for the free exciton in (pyH)PbBr3 (Ea = 0.010 eV). Analysis of temperature dependent luminescence lifetime data indicates another non-radiative decay process in (pyH)PbI3 at higher temperatures (Ea = 0.17 eV). A large increase in the luminescence lifetime of (pyH)PbI3 below 80 K is consistent with thermalization between triplet sublevels. Analysis of the luminescence power dependence for (pyH)PbI3 shows superlinear response suggestive of quenching by static traps.
Collapse
|
5
|
A Comparison between Triphenylmethyl and Triphenylsilyl Spirobifluorenyl Hosts: Synthesis, Photophysics and Performance in Phosphorescent Organic Light-Emitting Diodes. Molecules 2023; 28:5241. [PMID: 37446902 DOI: 10.3390/molecules28135241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/30/2023] [Accepted: 07/01/2023] [Indexed: 07/15/2023] Open
Abstract
This study presents the synthesis and characterization of two spirobifluorenyl derivatives substituted with either triphenylmethyl (SB-C) or triphenylsilyl (SB-Si) moieties for use as host materials in phosphorescent organic light-emitting diodes (PHOLED). Both molecules have similar high triplet energies and large energy gaps. Blue Ir(tpz)3 and green Ir(ppy)3 phosphorescent devices were fabricated using these materials as hosts. Surprisingly, SB-Si demonstrated superior charge-transporting ability compared to SB-C, despite having similar energies for their valence orbitals. In particular, SB-Si proved to be a highly effective host for both blue and green devices, resulting in maximum efficiencies of 12.6% for the Ir(tpz)3 device and 9.6% for the Ir(ppy)3 device. These results highlight the benefits of appending the triphenylsilyl moiety onto host materials and underscore the importance of considering the morphology of hosts in the design of efficient PHOLEDs.
Collapse
|
6
|
Abstract
Generating sustainable fuel from sunlight plays an important role in meeting the energy demands of the modern age. Herein, we report two-coordinate carbene-metal-amide (cMa, M = Cu(I) and Au(I)) complexes that can be used as sensitizers to promote the light-driven reduction of water to hydrogen. The cMa complexes studied here absorb visible photons (εvis > 103 M-1 cm-1), maintain long excited-state lifetimes (τ ∼ 0.2-1 μs), and perform stable photoinduced charge transfer to a target substrate with high photoreducing potential (E+/* up to -2.33 V vs Fc+/0 based on a Rehm-Weller analysis). We pair these coinage metal complexes with a cobalt-glyoxime electrocatalyst to photocatalytically generate hydrogen and compare the performance of the copper- and gold-based cMa complexes. We also find that the two-coordinate complexes herein can perform photodriven hydrogen production from water without the addition of the cobalt-glyoxime electrocatalyst. In this "catalyst-free" system, the cMa sensitizer partially decomposes to give metal nanoparticles that catalyze water reduction. This work identifies two-coordinate coinage metal complexes as promising abundant metal, solar fuel photosensitizers that offer exceptional tunability and photoredox properties.
Collapse
|
7
|
Interactions between nonfullerene acceptors lead to unstable ternary organic photovoltaic cells. Proc Natl Acad Sci U S A 2023; 120:e2301118120. [PMID: 37252984 PMCID: PMC10266035 DOI: 10.1073/pnas.2301118120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 04/07/2023] [Indexed: 06/01/2023] Open
Abstract
For organic photovoltaic (OPV) devices to achieve consistent performance and long operational lifetimes, organic semiconductors must be processed with precise control over their purity, composition, and structure. This is particularly important for high volume solar cell manufacturing where control of materials quality has a direct impact on yield and cost. Ternary-blend OPVs containing two acceptor-donor-acceptor (A-D-A)-type nonfullerene acceptors (NFAs) and a donor have proven to be an effective strategy to improve solar spectral coverage and reduce energy losses beyond that of binary-blend OPVs. Here, we show that the purity of such a ternary is compromised during blending to form a homogeneously mixed bulk heterojunction thin film. We find that the impurities originate from end-capping C=C/C=C exchange reactions of A-D-A-type NFAs, and that their presence influences both device reproducibility and long-term reliability. The end-capping exchange results in generation of up to four impurity constituents with strong dipolar character that interfere with the photoinduced charge transfer process, leading to reduced charge generation efficiency, morphological instabilities, and an increased vulnerability to photodegradation. As a consequence, the OPV efficiency falls to less than 65% of its initial value within 265 h when exposed to up to 10 suns intensity illumination. We propose potential molecular design strategies critical to enhancing the reproducibility as well as reliability of ternary OPVs by avoiding end-capping reactions.
Collapse
|
8
|
Polarizable Anionic Sublattices Can Screen Molecular Dipoles in Noncentrosymmetric Inorganic-Organic Hybrids. ACS APPLIED MATERIALS & INTERFACES 2023; 15:18006-18011. [PMID: 36987567 PMCID: PMC10103049 DOI: 10.1021/acsami.2c20648] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 03/13/2023] [Indexed: 06/19/2023]
Abstract
We report the growth and photophysical characterization of two polar hybrid lead halide phases, methylenedianiline lead iodide and bromide, (MDA)Pb2I6 and (MDA)Pb2Br6, respectively. The phases crystallize in noncentrosymmetric space group Fdd2, which produces a highly oriented molecular dipole moment that gives rise to second harmonic generation (SHG) upon excitation at 1064 nm. While both compositions are isostructural, the size dependence of the SHG signal suggests that the bromide exhibits a stronger phase-matching response whereas the iodide exhibits a significantly weaker non-phase-matching signal. Similarly, fluorescence from (MDA)Pb2Br6 is observed around 630 nm below 75 K whereas only very weak luminescence from (MDA)Pb2I6 can be seen. We attribute the contrasting optical properties to differences in the character of the halide sublattice and postulate that the increased polarizability of the iodide ions acts to screen the local dipole moment, effectively reducing the local electric field in the crystals.
Collapse
|
9
|
Sparkling Organic Phosphorescence from Fluorinated Tetrathia[7]helicenes: Synthesis and Photophysical, Electrochemical and Computational Studies. Chemistry 2023; 29:e202300339. [PMID: 36939032 DOI: 10.1002/chem.202300339] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 03/21/2023]
Abstract
Structure-property correlations in the thiahelicene family are often not trivial since most of the functional groups present on the helical scaffold modify the conjugation size of the π-system. Selecting fluorine containing groups to provide strong inductive effects without interacting with low-lying orbitals of the system could be the way to overcome the issue. Here we report a study on three fluorine-functionalized tetrathia[7]helicenes highlighting interesting correlations between the position of the functional groups and the conjugated skeleton properties. Helicenes Heli-F2 and Heli-CF-F2 were prepared by photoinduced isomerization-electrocyclization (the Mallory photocyclization) of the corresponding fluorinated benzodithienyl-ethenes Alk-F2 and Alk-CF-F2, which were prepared, in high yields, through stereo-conservative Stille reaction. Notably these helicenes were found to display green phosphorescence around 530-550 nm and the studies suggest an efficient spin orbit coupling mechanism in these high-energy triplet non-planar conjugated molecules. Both helicenes and their precursors were thoroughly characterized by means of optical and electrochemical measurements while DFT calculations enable to define a rationale on their structure-property correlations.
Collapse
|
10
|
Correction to " 'Quick-Silver' from a Systematic Study of Highly Luminescent, Two-Coordinate, d 10 Coinage Metal Complexes. J Am Chem Soc 2023; 145:1470-1471. [PMID: 36576490 DOI: 10.1021/jacs.2c12680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
11
|
Correction to "Highly Efficient Photo- and Electroluminescence from Two-Coordinate Cu(I) Complexes Featuring Nonconventional N-Heterocyclic Carbenes". J Am Chem Soc 2023; 145:746-747. [PMID: 36574635 DOI: 10.1021/jacs.2c12676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
12
|
Abstract
Two-coordinate carbene-MI-amide (cMa, MI = Cu, Ag, Au) complexes have emerged as highly efficient luminescent materials for use in a variety of photonic applications due to their extremely fast radiative rates through thermally activated delayed fluorescence (TADF) from an interligand charge transfer (ICT) process. A series of cMa derivatives was prepared to examine the variables that affect the radiative rate, with the goal of understanding the parameters that control the radiative TADF process in these materials. We find that blue-emissive complexes with high photoluminescence efficiencies (ΦPL > 0.95) and fast radiative rates (kr = 4 × 106 s-1) can be achieved by selectively extending the π-system of the carbene and amide ligands. Of note is the role played by the increased separation between the hole and electron in the ICT excited state. Analysis of temperature-dependent luminescence data and theoretical calculations indicate that the hole-electron separation exerts a primary effect on the energy gap between the lowest-energy singlet and triplet states (ΔEST) while keeping the radiative rate for the singlet state relatively unchanged. This interpretation provides guidelines for the design of new cMa derivatives with even faster radiative rates in addition to those with slower radiative rates and thus extended excited state lifetimes.
Collapse
|
13
|
Abstract
ConspectusSymmetry breaking charge transfer (SBCT) is a process in which a pair of identical chromophores absorb a photon and use its energy to transfer an electron from one chromophore to the other, breaking the symmetry of the chromophore pair. This excited state phenomenon is observed in photosynthetic organisms where it enables efficient formation of separated charges that ultimately catalyze biosynthesis. SBCT has also been proposed as a means for developing photovoltaics and photocatalytic systems that operate with minimal energy loss. It is known that SBCT in both biological and artificial systems is in part made possible by the local environment in which it occurs, which can move to stabilize the asymmetric SBCT state. However, how environmental degrees of freedom act in concert with steric and structural constraints placed on a chromophore pair to dictate its ability to generate long-lived charge pairs via SBCT remain open topics of investigation.In this Account, we compare a broad series of dipyrrin dimers that are linked by distinct bridging groups to discern how the spatial separation and mutual orientation of linked chromophores and the structural flexibility of their linker each impact SBCT efficiency. Across this material set, we observe a general trend that SBCT is accelerated as the spatial separation between dimer chromophores decreases, consistent with the expectation that the electronic coupling between these units varies exponentially with their separation. However, one key observation is that the rate of charge recombination following SBCT was found to slow with decreasing interchromophore separation, rather than speed up. This stems from an enhancement of the dimer's structural rigidity due to increasing steric repulsion as the length of their linker shrinks. This rigidity further inhibits charge recombination in systems where symmetry has already enforced zero HOMO-LUMO overlap. Additionally, for the forward transfer, the active torsion is shown to increase LUMO-LUMO coupling, allowing for faster SBCT within bridging groups.By understanding trends for how rates of SBCT and charge recombination depend on a dimer's internal structure and its environment, we identify design guidelines for creating artificial systems for driving sustained light-induced charge separation. Such systems can find application in solar energy technologies and photocatalytic applications and can serve as a model for light-induced charge separation in biological systems.
Collapse
|
14
|
Dynamics of rotation in two‐coordinate thiazolyl copper(I) carbazolyl complexes. Appl Organomet Chem 2022. [DOI: 10.1002/aoc.6728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
15
|
Editorial for the special issue of Materials Horizons in honor of Seth Marder. MATERIALS HORIZONS 2022; 9:15-16. [PMID: 34918014 DOI: 10.1039/d1mh90068d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Jean-Luc Brédas, Zhenan Bao, Thuc-Quyen Nguyen, and Mark E. Thompson introduce the Materials Horizons special issue in honor of Seth Marder.
Collapse
|
16
|
pi-Extension of Heterocycles via a Pd-Catalyzed Heterocyclic Aryne Annulation: pi-Extended Donors for TADF Emitters. Chem Sci 2022; 13:5884-5892. [PMID: 35685807 PMCID: PMC9132060 DOI: 10.1039/d2sc01788a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 05/03/2022] [Indexed: 11/21/2022] Open
Abstract
We report the annulation of heterocyclic building blocks to access pi-extended polycyclic aromatic hydrocarbons (PAHs). The method involves the trapping of short-lived hetarynes with catalytically-generated biaryl palladium intermediates and allows...
Collapse
|
17
|
Molecular Alignment of Homoleptic Iridium Phosphors in Organic Light-Emitting Diodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2102882. [PMID: 34302388 DOI: 10.1002/adma.202102882] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/26/2021] [Indexed: 06/13/2023]
Abstract
The orientation of facial (fac) tris-cyclometalated iridium complexes in doped films prepared by vacuum deposition is investigated by altering the physical shape and electronic asymmetry in the molecular structure. Angle-dependent photoluminescence spectroscopy and Fourier-plane imaging microscopy show that the orientation of roughly spherical fac-tris(2-phenylpyridyl)iridium (Ir(ppy)3 ) is isotropic, whereas complexes that are oblate spheroids, fac-tris(mesityl-2-phenyl-1H-imidazole)iridium (Ir(mi)3 ) and fac-tris((3,5-dimethyl-[1,1'-biphenyl]-4-yl)-2-phenyl-1H-imidazole)iridium (Ir(mip)3 ), have a net horizontal alignment of their transition dipole moments. Optical anisotropy factors of 0.26 and 0.15, respectively, are obtained from the latter complexes when doped into tris(4-(9H-carbazol-9-yl)phenyl)amine host thin films. The horizontal alignment is attributed to the favorable van der Waals interaction between the oblate Ir complexes and host material. Trifluoromethyl groups substituted on one polar face of the Ir(ppy)3 and Ir(mi)3 complexes introduce chemical asymmetries in the molecules at the expense of their oblate shapes. The anisotropy factors of films doped with these substituted derivatives are lower relative to the parent complexes, indicating that the fluorinated patches reinforce horizontal alignment during deposition. High efficiencies obtained from organic light emitting diodes prepared using the Ir dopants is attributed, in part, to improved outcoupling of electroluminescence brought about by molecular alignment.
Collapse
|
18
|
A Luminescent Two-Coordinate Au I Bimetallic Complex with a Tandem-Carbene Structure: A Molecular Design for the Enhancement of TADF Radiative Decay Rate. Chemistry 2021; 27:6191-6197. [PMID: 33561304 DOI: 10.1002/chem.202100512] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Indexed: 12/15/2022]
Abstract
A luminescent bimetallic AuI complex comprised of N-heterocyclic carbene (NHC) and carbazole (Cz) ligands, that is, (NHC')Au(NHC)AuCz has been synthesized and studied. Both carbene ligands in the bimetallic complex act as electron acceptors in tandem to increase the energy separation between the ground and excited state, which is higher than those found in either monometallic analogue, (NHC)AuCz and (NHC')AuCz. A coplanar geometry designed into the tandem complex ensures sufficient electronic coupling between the π-orbitals of the ligands to impart a strong oscillator strength to the singlet intra-ligand charge-transfer (1 ICT) transition. Theoretical modelling indicates that the emissive ICT excited state involves both NHC ligands. The tandem complex gives blue luminescence (λmax =480 nm) with a high photoluminescent quantum yield (ΦPL =0.80) with a short decay lifetime (τ=0.52 μs). Temperature-dependent photophysical studies indicate that emission is via thermally assisted delayed fluorescence (TADF) and give a small singlet-triplet energy difference (ΔEST =50 meV, 400 cm-1 ) consistent with the short TADF lifetime.
Collapse
|
19
|
Phosphorescent monometallic and bimetallic two-coordinate Au(I) complexes with N-heterocyclic carbene and aryl ligands. Inorganica Chim Acta 2021. [DOI: 10.1016/j.ica.2020.120188] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
20
|
In Vivo Experimental and Analytical Studies for Bevacizumab Diffusion Coefficient Measurement in the Rabbit Vitreous Humor. JOURNAL OF HEAT TRANSFER 2021; 143:032101. [PMID: 33612856 PMCID: PMC7871997 DOI: 10.1115/1.4049033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 10/21/2020] [Indexed: 05/30/2023]
Abstract
In order to measure the effective diffusion coefficient D of Bevacizumab (Avastin, Genentech) in the vitreous humor, a new technique is developed based on the "contour method" and in vivo optical coherence tomography measurements. After injection of Bevacizumab-fluorescein conjugated compound solution into the rabbit eye, the contours of drug concentration distribution at the subsurface of injection were tracked over time. The 2D contours were extrapolated to 3D contours using reasonable assumptions and a numerically integrated analytical model was developed for the theoretical contours for the irregularly shaped drug distribution in the experimental result. By floating the diffusion coefficient, different theoretical contours were constructed and the least-squares best fit to the experimental contours was performed at each time point to get the best fit solution. The approach generated consistent diffusion coefficient values based on the experiments on four rabbit eyes over a period of 3 h each, which gave D = 1.2 ± 0.6 × 10 - 6 cm 2 / s , and the corresponding theoretical contours matched well with the experimental contours. The quantitative measurement of concentration using optical coherence tomography and fluorescein labeling gives a new approach for the "noncontact" in vivo drug distribution measurement within vitreous.
Collapse
|
21
|
Synthesis and Characterization of Zinc(II) Complexes Bearing 4-Acridinol and 1-Phenazinol Ligands. Inorg Chem 2021; 60:866-871. [PMID: 33395530 DOI: 10.1021/acs.inorgchem.0c02942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis and characterization of zinc(II) chelates bearing acridin-4-ol (A), phenazin-1-ol (P), and benzo[b]phenazin-1-ol (bP) are presented. The formation of homoleptic (ZnX2) or heteroleptic (ZnX1) products can be controlled by stochiometric or excess amounts of zinc(II) acetylacetonate monohydrate, Zn(acac)2, respectively. Electrochemical and photophysical studies show that the homoleptic complexes (ZnA2, ZnP2, and ZnbP2) have ligand-centered properties inherited from the corresponding free ligands. Calculations using density functional theory (DFT) agree with the observed experimental ligand-centered photophysical and electrochemical behavior.
Collapse
|
22
|
Influence of Dimethyl Sulfoxide on the Structural Topology during Crystallization of PbI 2. Inorg Chem 2020; 59:16799-16803. [PMID: 33164500 DOI: 10.1021/acs.inorgchem.0c02056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hybrid metal-organic halides are an exciting class of materials that offer the opportunity to examine how fundamental aspects of chemical bonding can influence the structural topology. In this work, we describe how solvent adducts of lead halides can influence the crystallization and subsequent annealing of these hybrid phases. While the size and shape of organic molecules are known to govern the final topology of the hybrid, we show that the affinity of solvent molecules for Pb ions may also play a previously underappreciated role.
Collapse
|
23
|
Dose Comparison of Epsilon-Aminocaproic Acid to Reduce Blood Loss in Infants Undergoing Cranial Vault Reconstruction Surgery: A Retrospective Pilot Study. J Clin Anesth 2020; 66:109952. [PMID: 32521431 DOI: 10.1016/j.jclinane.2020.109952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 05/21/2020] [Accepted: 05/29/2020] [Indexed: 11/15/2022]
|
24
|
Vibrational Sum Frequency Generation Study of the Interference Effect on a Thin Film of 4,4'-Bis( N-carbazolyl)-1,1'-biphenyl (CBP) and Its Interfacial Orientation. ACS APPLIED MATERIALS & INTERFACES 2020; 12:26515-26524. [PMID: 32406227 DOI: 10.1021/acsami.0c01394] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Molecular organization of vapor-deposited organic molecules in the active layer of organic light-emitting diodes (OLEDs) has been a matter of great interest as it directly influences various optoelectronic properties and the overall performance of the devices. Contrary to the general assumption of isotropic molecular orientation in vacuum-deposited thin-film OLEDs, it is possible to achieve an anisotropic molecular distribution at or near the surface under controlled experimental conditions. In this study, we have used interface-specific vibrational sum frequency generation (VSFG) spectroscopy to determine the orientation of a low-molecular weight OLED material, 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), at free (air) and buried (CaF2) interfaces. VSFG spectra were measured at four different polarization combinations for five different thicknesses of the CBP film. The spectral shift and VSFG intensity changes with the film thickness can be accurately modeled by considering the optical interference effect of the signals coming from the CBP/air and CBP/CaF2 interfaces. A global fitting of the experimental spectra for all thicknesses along with theoretical simulations reveal that the long molecular axis of CBP is oriented at an angle of ∼58° (47-70°) from the surface normal at the air/CBP interface, whereas at the CBP/CaF2 interface, the angle is ∼48° (43-52°). Such a change in the angle (∼10°) suggests that the CBP molecule tends to orient more vertically (edge-on) at the buried CaF2 interface, which may be attributed to the intermolecular π-π stacking interaction between adjacent CBP molecules.
Collapse
|
25
|
Highly Efficient Deep Blue Luminescence of 2-Coordinate Coinage Metal Complexes Bearing Bulky NHC Benzimidazolyl Carbene. Front Chem 2020; 8:401. [PMID: 32457877 PMCID: PMC7225363 DOI: 10.3389/fchem.2020.00401] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 04/16/2020] [Indexed: 12/02/2022] Open
Abstract
The structural, photophysical and electrochemical properties of three luminescent 2-coordinate coinage metal (i.e., M = Cu, Ag, Au) complexes bearing a sterically bulky benzimidazolyl carbene, 1,3-bis(2,6-diisopropylphenyl)-1-H-benzo[d]imidazol-2-ylidene (BZI), and carbazolide (Cz) as the anionic ligand were investigated. All the complexes emit in the deep blue region (~430 nm) with relatively narrow spectra (full width at half maximum = 44 nm, 2,300 cm−1) characterized by vibronic fine structure in nonpolar media (methylcyclohexane at room temperature), and with high photoluminescence quantum yields (ΦPL > 80%) and radiative rate constants (kr ~ 7.8 × 105 s−1). The luminescence is solvatochromic, undergoing a red-shift in a polar solvent (CH2Cl2) at room temperature that are accompanied by a decrease in quantum yields (ΦPL < 23%) and radiative rate constants (kr < 4.0 × 104 s−1), whereas the non-radiative rate constants remain nearly constant (knr ~ 1.0 × 105 s−1). The radiative rate is controlled via thermally assisted delayed fluorescence (TADF) and temperature-dependent luminescence studies of the gold complex (AuBZI) in methylcyclohexane solution reveal an energy difference between the lowest singlet and triplet excited states of 920 cm−1. An organic light-emitting diode (OLED) fabricated using AuBZI as a luminescent dopant has an external quantum efficiency of 12% and narrow, deep-blue emission (CIE = 0.16, 0.06).
Collapse
|
26
|
Molecular dynamics of four-coordinate carbene-Cu(I) complexes employing tris(pyrazolyl)borate ligands. Polyhedron 2020. [DOI: 10.1016/j.poly.2020.114381] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
27
|
Enhancement of the Luminescent Efficiency in Carbene-Au(I)-Aryl Complexes by the Restriction of Renner–Teller Distortion and Bond Rotation. J Am Chem Soc 2020; 142:6158-6172. [DOI: 10.1021/jacs.9b13755] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
28
|
Correction to “Highly Efficient Photo- and Electroluminescence from Two-Coordinate Cu(I) Complexes Featuring Nonconventional N-Heterocyclic Carbenes”. J Am Chem Soc 2019; 141:18356. [DOI: 10.1021/jacs.9b11526] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
29
|
Improving Photocatalysis for the Reduction of CO 2 through Non-covalent Supramolecular Assembly. J Am Chem Soc 2019; 141:14961-14965. [PMID: 31490687 DOI: 10.1021/jacs.9b07067] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We report the enhancement of photocatalytic performance by introduction of hydrogen-bonding interactions to a Re bipyridine catalyst and Ru photosensitizer system (ReDAC/RuDAC) by the addition of amide substituents, with carbon monoxide (CO) and carbonate/bicarbonate as products. This system demonstrates a more-than-3-fold increase in turnover number (TONCO = 100 ± 4) and quantum yield (ΦCO = 23.3 ± 0.8%) for CO formation compared to the control system using unsubstituted Ru photosensitizer (RuBPY) and ReDAC (TONCO = 28 ± 4 and ΦCO = 7 ± 1%) in acetonitrile (MeCN) with 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as sacrificial reductant. In dimethylformamide (DMF), a solvent that disrupts hydrogen bonds, the ReDAC/RuDAC system showed a decrease in catalytic performance while the control system exhibited an increase, indicating the role of hydrogen bonding in enhancing the photocatalysis for CO2 reduction through supramolecular assembly. The similar properties of RuDAC and RuBPY demonstrated in lifetime measurements, spectroscopic analysis, and electrochemical and spectroelectrochemical studies revealed that the enhancement in photocatalysis is due not to differences in intrinsic properties of the catalyst or photosensitizer, but to hydrogen-bonding interactions between them.
Collapse
|
30
|
Tuning State Energies for Narrow Blue Emission in Tetradentate Pyridyl-Carbazole Platinum Complexes. Inorg Chem 2019; 58:12348-12357. [DOI: 10.1021/acs.inorgchem.9b01888] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
31
|
Systematic Control of the Orientation of Organic Phosphorescent Pt Complexes in Thin Films for Increased Optical Outcoupling. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1900921. [PMID: 31197907 DOI: 10.1002/adma.201900921] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 05/20/2019] [Indexed: 06/09/2023]
Abstract
Orienting light-emitting molecules relative to the substrate is an effective method to enhance the optical outcoupling of organic light-emitting devices. Platinum(II) phosphorescent complexes enable facile control of the molecular alignment due to their planar structures. Here, the orientation of Pt(II) complexes during the growth of emissive layers is controlled by two different methods: modifying the molecular structure and using structural templating. Molecules whose structures are modified by adjusting the diketonate ligand of the Pt complex, dibenzo-(f,h)quinoxaline Pt dipivaloylmethane, (dbx)Pt(dpm), show an ≈20% increased fraction of horizontally aligned transition dipole moments compared to (dbx)Pt(dpm) doped into a 4,4'-bis(N-carbazolyl)-1,1'-biphenyl, CBP, host. Alternatively, a template composed of highly ordered 3,4,9,10-perylenetetracarboxylic dianhydride monolayers is predeposited to drive the alignment of a subsequently deposited emissive layer comprising (2,3,7,8,12,13,17,18-octaethyl)-21H,23H-porphyrinplatinum(II) doped into triindolotriazine. This results in a 60% increase in horizontally aligned transition dipole moments compared to the film deposited in the absence of the template. The findings provide a systematic route for controlling molecular alignment during layer growth, and ultimately to increase the optical outcoupling in organic light-emitting diodes.
Collapse
|
32
|
Performance of enhanced DuBois type water reduction catalysts (WRC) in artificial photosynthesis - effects of various proton relays during catalysis. Faraday Discuss 2019; 215:141-161. [PMID: 30942209 DOI: 10.1039/c8fd00162f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Inspired by natural photosynthesis, features such as proton relays have been integrated into water reduction catalysts (WRC) for effective production of hydrogen. Research by DuBois et al. showed the crucial influence of these relays, largely in the form of pendant amine functions. In this work catalysts are presented containing innovative diphosphinoamine ligands: [M(ii)Cl2(PNP-C1)], [M(ii)(MeCN)2(PNP-C1)]2+, [M(ii)(PNP-C1)2]2+, and [M(ii)Cl(PNP-C2)]+ (M = Pt2+, Pd2+, Ni2+, Co2+; PNP-C1 = N,N-bis{(di(2-methoxyphenyl)phosphino)methyl}-N-alkylamine, PNP-C2 = N,N-bis{(di(2-methoxyphenyl)phosphino)ethyl}-N-alkylamine and alkyl = Me, Et, iso-Pr, Bz). Synthetic strategies and detailed characterisation are covered, including 1H-, 13C-, and 31P-NMR analysis, mass spectroscopy and single crystal X-ray diffractometry (XRD). The catalytic properties have been explored by changing the pendant amines and auxiliary methoxy coordination sites, as well as enlarging the ligand backbone. Moreover, confirmed by density functional theory (DFT) calculations based on XRD data in vacuo and solvent environment, two very different catalytic cycles are proposed. PNP-C1 shows a classical proton relay, whereas PNP-C2 allows an additional coordination of nitrogen, acting optionally like a pincer. Through new insights into efficiency and stability-increasing influences of proton relays in general, their number per metal centre, an enlarged ligand backbone and the use of solvato instead of halogenido complexes, substantial improvements have been made in catalytic performance over the DuBois et al. catalysts and recently self-made WRCs. The turnover number (TON) related to the single site of cost-efficient nickel WRCs is increased from 11.4 to 637, whereas a corresponding palladium catalyst gives TON as high as 2289.
Collapse
|
33
|
Correction to “ ‘Quick-Silver’ from a Systematic Study of Highly Luminescent, Two-Coordinate, d 10 Coinage Metal Complexes”. J Am Chem Soc 2019; 141:10118. [DOI: 10.1021/jacs.9b06147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
34
|
"Quick-Silver" from a Systematic Study of Highly Luminescent, Two-Coordinate, d 10 Coinage Metal Complexes. J Am Chem Soc 2019; 141:8616-8626. [PMID: 31062972 DOI: 10.1021/jacs.9b03657] [Citation(s) in RCA: 130] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A systematic study is presented on the physical and photophysical properties of isoelectronic and isostructural Cu, Ag, and Au complexes with a common amide (N-carbazolyl) and two different carbene ligands (i.e., CAAC = (5 R,6 S)-2-(2,6-diisopropylphenyl)-6-isopropyl-3,3,9-trimethyl-2-azaspiro[4.5]decan-2-ylidene, MAC = 1,3-bis(2,6-diisopropylphenyl)-5,5-dimethyl-4-keto-tetrahydropyridylidene). The crystal structures of the (carbene)M(I)(N-carbazolyl) (MCAAC) and (MAC)M(I)(N-carbazolyl) (MMAC) complexes show coplanar carbene and carbzole ligands and C-M-N bond angles of ∼180°. The electrochemical properties and energies for charge transfer (CT) absorption and emission compounds are not significantly affected by the choice of metal ion. All six of the (carbene)M(Cz) complexes examined here display high photoluminescence quantum yields of 0.8-1.0. The compounds have short emission lifetimes (τ = 0.33-2.8 μs) that fall in the order Ag < Au < Cu, with the lifetimes of (carbene)Ag(Cz) roughly a factor of 10 shorter than for (carbene)Cu(Cz) complexes. Detailed temperature-dependent photophysical measurements (5-325 K) were carried out to determine the singlet and triplet emission lifetimes (τfl and τph, respectively) and the energy difference between the singlet and triplet excited state, Δ ES1-T1. The τfl values range between 20 and 85 ns, and the τph values are in the 50-200 μs regime. The emission at room temperature is due exclusively to E-type delayed fluorescence or TADF (i.e., T1→ΔS1→S0+hν ). The emission rate at room temperature is fully governed by Δ ES1-T1, with the silver complexes giving Δ ES1-T1 values of 150-180 cm-1 (18-23 meV), whereas the gold and copper complexes give values of 570-590 cm-1 (70-73 meV).
Collapse
|
35
|
Molecular Orientation of Poly-3-hexylthiophene at the Buried Interface with Fullerene. J Phys Chem Lett 2019; 10:1757-1762. [PMID: 30908051 DOI: 10.1021/acs.jpclett.9b00498] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Molecular orientation at the donor-acceptor interface plays a crucial role in determining the efficiency of organic semiconductor materials. We have used vibrational sum frequency generation spectroscopy to determine the orientation of poly-3-hexylthiophene (P3HT) at the planar buried interface with fullerene (C60). The thiophene rings of P3HT have been found to tilt significantly toward C60, making an average angle θ ≈ 49° ± 10° between the plane of the ring and the interface. Such tilt may be attributed to π-π stacking interactions between P3HT and C60 and may facilitate efficient charge transfer between donor and acceptor. Upon annealing, the thiophene rings tilt away from the interface by Δθ = 12-19°. This may be attributed to higher crystallinity of annealed P3HT that propagates all the way to the interface, resulting in more "edge-on" orientation, which is consistent with the observed red-shift by ∼6 cm-1 and spectral narrowing of the C=C stretch bands.
Collapse
|
36
|
Epidural analgesia for percutaneous kyphoplasty in a patient with multiple medical comorbidities. Avicenna J Med 2019; 9:75-77. [PMID: 31143700 PMCID: PMC6530273 DOI: 10.4103/ajm.ajm_73_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Kyphoplasty is a minimally invasive procedure intended to stabilize the fractured bone and restore bone height. It involves percutaneous introduction of an inflatable bone tamp into a fractured vertebral body, followed by injection of bone cement into the ballooned pocket. Anesthetic options typically considered for this procedure include intravenous sedation or general anesthesia. These patients are often elderly, frail, in significant pain, and may poorly tolerate sedation or general anesthesia in the prone position. Spinal anesthesia has been suggested as an alternative method. However, it has major limitations. We would like to report a case of a 79-year-old patient with multiple comorbidities, who presented for kyphoplasty, where epidural anesthesia was conducted and successfully provided adequate analgesia as well as optimal surgical conditions.
Collapse
|
37
|
Highly Efficient Photo- and Electroluminescence from Two-Coordinate Cu(I) Complexes Featuring Nonconventional N-Heterocyclic Carbenes. J Am Chem Soc 2019; 141:3576-3588. [PMID: 30768250 DOI: 10.1021/jacs.8b12397] [Citation(s) in RCA: 157] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A series of six luminescent two-coordinate Cu(I) complexes were investigated bearing nonconventional N-heterocyclic carbene ligands, monoamido-aminocarbene (MAC*) and diamidocarbene (DAC*), along with carbazolyl (Cz) as well as mono- and dicyano-substituted Cz derivatives. The emission color can be systematically varied over 270 nm, from violet to red, through proper choice of the acceptor (carbene) and donor (carbazolyl) groups. The compounds exhibit photoluminescent quantum efficiencies up to 100% in fluid solution and polystyrene films with short decay lifetimes (τ ≈ 1 μs). The radiative rate constants for the Cu(I) complexes ( kr = 105-106 s-1) are comparable to state of the art phosphorescent emitters with noble metals such as Ir and Pt. All complexes show strong solvatochromism due to the large dipole moment of the ground states and the transition dipole moment that is in the opposite direction. Temperature-dependent studies of (MAC*)Cu(Cz) reveal a small energy separation between the lowest singlet and triplet states (Δ ES1-T1 = 500 cm-1) and an exceptionally large zero-field splitting (ZFS = 85 cm-1). Organic light-emitting diodes (OLEDs) fabricated with (MAC*)Cu(Cz) as a green emissive dopant have high external quantum efficiencies (EQE = 19.4%) and brightness of 54 000 cd/m2 with modest roll-off at high currents. The complex can also serve as a neat emissive layer to make highly efficient OLEDs (EQE = 16.3%).
Collapse
|
38
|
Eliminating nonradiative decay in Cu(I) emitters: >99% quantum efficiency and microsecond lifetime. Science 2019; 363:601-606. [PMID: 30733411 DOI: 10.1126/science.aav2865] [Citation(s) in RCA: 308] [Impact Index Per Article: 61.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 01/02/2019] [Indexed: 12/24/2022]
Abstract
Luminescent complexes of heavy metals such as iridium, platinum, and ruthenium play an important role in photocatalysis and energy conversion applications as well as organic light-emitting diodes (OLEDs). Achieving comparable performance from more-earth-abundant copper requires overcoming the weak spin-orbit coupling of the light metal as well as limiting the high reorganization energies typical in copper(I) [Cu(I)] complexes. Here we report that two-coordinate Cu(I) complexes with redox active ligands in coplanar conformation manifest suppressed nonradiative decay, reduced structural reorganization, and sufficient orbital overlap for efficient charge transfer. We achieve photoluminescence efficiencies >99% and microsecond lifetimes, which lead to an efficient blue-emitting OLED. Photophysical analysis and simulations reveal a temperature-dependent interplay between emissive singlet and triplet charge-transfer states and amide-localized triplet states.
Collapse
|
39
|
Rapid Multiscale Computational Screening for OLED Host Materials. ACS APPLIED MATERIALS & INTERFACES 2019; 11:5276-5288. [PMID: 30640428 DOI: 10.1021/acsami.8b16225] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The design of new host materials for phosphorescent organic light emitting diodes (OLEDs) is challenging because several physical property requirements must be met simultaneously. A triplet energy ( ET) higher than that of the chosen emitting dopant, appropriate highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels, good charge carrier transport, and high stability are all required. Here, computational methods were used to screen structures to find the most promising candidates for OLED hosts. The screening was carried out in three Tiers. The Tier 1 selection, based on density functional theory calculations, identified a set of eight molecular structures with ET > 2.9 eV, suitable for hosting blue phosphorescent dopants such as iridium(III)bis((4,6-di-fluorophenyl)-pyridinato-N,C2')picolinate. Phenanthro[9,10- d]imidazole was chosen as the starting point for the Tier 2 selection. Thirty-seven unique molecular structures were enumerated by isoelectronic nitrogen transmutation of up to two CH fragments of the phenanthrene. Three molecules, that is, imidazo[4,5- f]-phenanthrolines with nitrogens at the 1,10-, 3,8-, and 4,7-positions, were selected for Tier 3, which involved the use of molecular dynamics simulations and electron coupling calculations to predict differences in charge transport between the three materials. The three were explored experimentally through synthesis and device fabrication. The singlet, triplet, and frontier orbital energies computed using single-molecule density functional theory calculations ( Tiers 1 and 2) were consistent with the experimental values in a fluid solution, and the multiscale modeling scheme ( Tier 3) correctly predicted the poor device performance of one material. We conclude that screening host materials using only single-molecule quantum mechanical data was not sufficient to predict whether a given material would make a good OLED host with certainty; however, they can be used to screen out materials that are destined to fail due to low singlet/triplet energies or a poor match of the frontier orbital energies to the dopant or transport materials.
Collapse
|
40
|
Symmetry breaking charge transfer as a means to study electron transfer with no driving force. Faraday Discuss 2019; 216:379-394. [DOI: 10.1039/c8fd00201k] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Herein we explore the symmetry breaking charge transfer process in two dipyrrin-based bichromophoric systems.
Collapse
|
41
|
Anionic order and band gap engineering in vacancy ordered triple perovskites. Chem Commun (Camb) 2019; 55:3164-3167. [DOI: 10.1039/c8cc09947b] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Exchanging the iodide for bromide on Cs3Bi2Br9 redshifts the absorption band while maintaining the Cs3Bi2Br9 structure.
Collapse
|
42
|
Tetra‐Aza‐Pentacenes by means of a One‐Pot Friedländer Synthesis. Chemistry 2018; 25:1472-1475. [DOI: 10.1002/chem.201805655] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Indexed: 11/10/2022]
|
43
|
Regional analgesia in neonates undergoing thoracoabdominal surgeries: A pilot study. J Neonatal Perinatal Med 2018; 12:73-79. [PMID: 30320598 DOI: 10.3233/npm-1827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVE The primary aim of this pilot study was to assess feasibility and to evaluate if peri-operative pain management with regional analgesia resulted in decreased use of narcotic medication and earlier return to preoperative respiratory/nutritional status. STUDY DESIGN Cases were defined as infants who received regional analgesia as part of their perioperative anesthetic management. Controls were matched for surgical procedures without regional analgesia. RESULTS Fifteen cases were identified and matched with 17 controls. Infants undergoing inguinal hernia repair returned to baseline earlier and were not intubated. There was no difference in time to extubation in other thoracoabdominal surgeries. There was no difference in cumulative narcotic analgesia administered between the two groups. CONCLUSION Postoperative regional analgesia is feasible in neonates. Inguinal hernia repair with regional anesthesia was performed without intubation and returned to preoperative status earlier. No differences were observed with other surgeries. Further prospective, randomized, multicenter studies are needed.
Collapse
|
44
|
Abstract
Separation of triplet excitons produced by singlet fission is crucial for efficient application of singlet fission materials. While earlier works explored the first step of singlet fission, the formation of the correlated triplet pair state, the focus of recent studies has been on understanding the second step of singlet fission, the formation of independent triplets from the correlated pair state. We present the synthesis and excited-state dynamics of meta- and para-bis(ethynyltetracenyl)benzene dimers that are analogues to the ortho-bis(ethynyltetracenyl)benzene dimer reported by our groups previously. A comparison of the excited-state properties of these dimers allows us to investigate the effects of electronic conjugation and coupling on singlet fission between the ethynyltetracene units within a dimer. In the para isomer, in which the two chromophores are conjugated, the singlet exciton yields the correlated triplet pair state, from which the triplet excitons can decouple via molecular rotations. In contrast, the meta isomer in which the two chromophores are cross-coupled predominantly relaxes via radiative decay. We also report the synthesis and excited-state dynamics of two para dimers with different bridging units joining the ethynyltetracenes. The rate of singlet fission is found to be faster in the dimer with the bridging unit that has orbitals closer in energy to that of the ethynyltetracene chromophores.
Collapse
|
45
|
Abstract
The efficiency of an organic solar cell depends on the efficacy of exciton diffusion and dissociation processes, and this can be enhanced by reducing the exciton binding energy and increasing the exciton lifetime. Zinc chlorodipyrrin (ZCl) complexes exhibit reduced exciton binding energy due to ultrafast generation of intramolecular charge transfer (ICT) states via symmetry-breaking charge transfer in polar media. This Letter explores the fate of the ICT states using nanosecond transient absorption. In cyclohexane, ZCl undergoes intersystem crossing to produce triplets with ∼8 ns time constant (∼30% yield), and no ICT states are generated. However, in more polar solvents, triplets are generated within 1 ns via ICT state recombination with ∼3 times higher yield than produced via ISC. This high triplet yield in toluene (89%) and acetonitrile (76%) via ICT state recombination is a beneficial pathway to spin-protect the excited-state decay for additional charge generation from triplet excited states.
Collapse
|
46
|
Phase transition in amphiphilic poly(N-isopropylacrylamide): controlled gelation. Phys Chem Chem Phys 2018; 20:13623-13631. [PMID: 29737361 DOI: 10.1039/c8cp01609g] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Thermally reversible gelation of polymers is of converging interest in both the fundamental research and practical biomedical or pharmaceutical applications. While the block structure is widely reported to favor gelation, there are few studies regarding the behavior of amphiphilic random copolymers. Herein, hydrophobically modified poly(N-isopropylacrylamide) (pNIPAM) polymers were designed and synthesized by reversible addition-fragmentation chain transfer (RAFT) copolymerization of NIPAM and butyl acrylate (BA). A library of polymer systems was created by varying the BA : NIPAM ratio, molecular weight (Mw) and concentrations. While a coil-to-globule transition induced microphase separation occurred in the dilute solution, diverse phase behaviors were observed by phase diagram study. A transparent gel phase was identified in p(NIPAM-co-BA) systems, which was missing in its block counterpart pNIPAM-b-pBA, and existed over a wider temperature range with increased BA content, Mw and concentrations. A dynamic rheological analysis revealed that the gel properties were strongly dependent on temperature, which regulated the interchain hydrophobic association, and the gel proved to be highly elastic, stable, reversible and self-healable under the optimized conditions. The p(NIPAM-co-BA) system will be highly desirable for injectable in situ forming hydrogel materials, and the study demonstrated here can be potentially extended to other amphiphilic pNIPAM copolymers.
Collapse
|
47
|
Synthesis and characterization of phosphorescent isomeric iridium complexes with a rigid cyclometalating ligand. Polyhedron 2018. [DOI: 10.1016/j.poly.2017.12.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
48
|
High-Performance Sub-Micrometer Channel WSe 2 Field-Effect Transistors Prepared Using a Flood-Dike Printing Method. ACS NANO 2017; 11:12536-12546. [PMID: 29219301 DOI: 10.1021/acsnano.7b06654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Printing technology has potential to offer a cost-effective and scalable way to fabricate electronic devices based on two-dimensional (2D) transition metal dichalcogenides (TMDCs). However, limited by the registration accuracy and resolution of printing, the previously reported printed TMDC field-effect transistors (FETs) have relatively long channel lengths (13-200 μm), thus suffering low current-driving capabilities (≤0.02 μA/μm). Here, we report a "flood-dike" self-aligned printing technique that allows the formation of source/drain metal contacts on TMDC materials with sub-micrometer channel lengths in a reliable way. This self-aligned printing technique involves three steps: (i) printing of gold ink on a WSe2 flake to form the first gold electrode, (ii) modifying the surface of the first gold electrode with a self-assembled monolayer (SAM) to lower the surface tension and render the surface hydrophobic, and (iii) printing of gold ink close to the SAM-treated first electrode at a certain distance. During the third step, the gold ink would first spread toward the edge of the first electrode and then get stopped by the hydrophobic SAM coating, ending up forming a sub-micrometer channel. With this printing technique, we have successfully downscaled the channel length to ∼750 nm and achieved enhanced on-state current densities of ∼0.64 μA/μm (average) and high on/off current ratios of ∼3 × 105 (average). Furthermore, with our high-performance printed WSe2 FETs, driving capabilities for quantum-dot light-emitting diodes (LEDs), inorganic LEDs, and organic LEDs have been demonstrated, which reveals the potential of using printed TMDC electronics for display backplane applications.
Collapse
|
49
|
Ultrasound to facilitate thoracic paravertebral catheter in severe scoliosis. J Clin Anesth 2017; 45:18-19. [PMID: 29247902 DOI: 10.1016/j.jclinane.2017.11.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 11/27/2017] [Accepted: 11/30/2017] [Indexed: 11/30/2022]
|
50
|
A reversible thermoresponsive sealant for temporary closure of ocular trauma. Sci Transl Med 2017; 9:9/419/eaan3879. [DOI: 10.1126/scitranslmed.aan3879] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 08/02/2017] [Accepted: 10/23/2017] [Indexed: 11/02/2022]
|