A comparative study of third-order nonlinear optical properties of silver phenylacetylide and related compounds via ultrafast optical Kerr effect measurements

Five Novel Silver-Based Coordination Polymers as Photoluminescent Sensing Platforms for the Detection of Nitrobenzene

Nitrobenzene (NB) is a highly toxic chemical and a cause for concern to human health and the environment. Hence, it is worth designing new efficient and robust sensing platforms for NB. In this study, we present three newly synthesized luminescent silver cluster-based coordination polymers, {[Ag10 (StBu)6 (CF3 COO)4 (hpbt)] (DMAc)2 (CH3 CN)2 }n (hpbt=N,N,N',N'N",N"-hexa(pyridine-4-yl)benzene-1,3,5-triamine), [Ag12 (StBu)6 (CF3 COO)6 (bpva)3 ]n (bpva=9,10-Bis(2-(pyridin-4-yl)vinyl)anthracene), and {[Ag12 (StBu)6 (CF3 COO)6 (bpb)(DMAc)2 (H2 O)2 ] (DMAc)2 }n (bpb=1,4-Bis(4-pyridyl)benzene) composed of Ag10 , Ag12 and Ag12 cluster cores, respectively, connected by multidentate pyridine linkers. In addition, two new luminescent polymorphic silver(I)-based coordination polymers, [Ag(CF3 COO)(dpa)]n (dpa=9,10-di(4-pyridyl)anthracene) referred to as Agdpa (H) and Agdpa (R), where H and R denote hexagon- and rod-like crystal shapes, respectively, have been prepared. The coordination polymers exhibit highly sensitive luminescence quenching effects to NB, attributed to the π-π stacking interactions between the polymers and NB as well as the electron-withdrawing character of NB.

cis/trans-[Pt(C∧N)(C≡CR)(CNBut)] Isomers: Synthesis, Photophysical, DFT Studies, and Chemosensory Behavior

cis/trans Isomerism can be a crucial factor for photophysical properties. Here, we report the synthesis and optical properties of a series of trans- and cis-alkynyl/isocyanide cycloplatinated compounds [Pt(C^∧N)(C≡CR)(CNBu^t)] [R = C₆H₄-4-OMe 1, 3-C₄H₃S 2; C^∧N = 2-(2,4-difluorophenyl)pyridine (dfppy) (a), 4-(2-pyridyl)benzaldehyde (ppy-CHO) (b)]. The trans-forms do not isomerize thermally in MeCN solution to the cis forms, but upon photochemical irradiation in this medium at 298 K, a variable isomerization to the cis forms was observed. This behavior is in good agreement with the theoretically calculated energy values. The trans/cis configuration, the identity of the cyclometalated, and the alkynyl ligand influence on the absorption and emission properties of the complexes in solution, polystyrene (PS) films, and solid state are reported. All complexes are efficient triplet emitters in all media (except for trans-1a and trans-2a in CH₂Cl₂ solution at 298 K), with emission wavelengths depending mainly on the cyclometalated ligand in the region 473-490 nm (dfppy), 510-550 (ppy-CHO), and quantum yields (ϕ) ranging from 18.5 to 40.7% in PS films. The combined photophysical data and time-dependent density functional theory calculations (TD-DFT) at the excited-state T₁ geometry reveal triplet excited states of ³L'LCT (C≡CR → C^∧N)/³IL (C^∧N) character with minor ³MLCT contribution. The dfppy (a) complexes show a greater tendency to aggregate in rigid media than the ppy-CHO (b) and the cis with respect to the trans, showing red-shifted structureless bands of ³MMLCT and/or excimer-like nature. Interestingly, trans-1a,2a and cis-1a,2a undergo significant changes in the ultraviolet (UV) and emission spectra with Hg²⁺ ions enabling their use for sensing of Hg²⁺ ions in solution. This is clearly shown by the hypsochromic shift and substantial decrease of the low-energy absorption band and an increase of the intensity of the emission in the MeCN solution upon the addition of a solution of Hg(ClO₄)₂ (1:5 molar ratio). Job's plot analysis estimated a 1:1 stoichiometry in the complexation mode of Hg²⁺ by trans-2a. The binding constant (log K) calculated for this system from absorption titration data resulted to be 2.56, and the limit of the detection (LOD) was 6.54 × 10^-7 M.

A Novel Photoluminescent Ag/Cu Cluster Exhibits a Chromic Photoluminescence Response towards Volatile Organic Vapors

A new Ag/Cu bimetallic cluster [Ag₁₀Cu₆(bdppthi)₂(C≡CPh)₁₂(EtOH)₂](ClO₄)₄ (1, bdppthi = N,N'-bis(diphenylphosphanylmethyl)-tetrahydroimidazole) exhibited strong phosphorescent (PL) emission at 644 nm upon excitation at 400 nm. Removal of the coordinated EtOH molecules in 1 resulted in derivative 1a, which exhibited significant red-shifted emission at 678 nm. The structure and PL of 1 was restored on exposure to EtOH vapor. Cluster 1a also exhibited a vapor-chromic PL response towards other common organic solvent vapors including acetone, MeOH and MeCN. A PMMA film of 1a was developed as a reusable visible sensor for MeCN.

Ditopic Phosphide Oxide Group: A Rigidifying Lewis Base to Switch Luminescence and Reactivity of a Disilver Complex

Heterodentate phosphines containing anionic organophosphorus groups remain virtually unexplored ligands in the coordination chemistry of coinage metals. A hybrid phosphine-phosphine oxide (o-Ph₂PC₆H₄)₂P(O)H (HP³O) readily forms the disilver complex [Ag₂(P³O)₂] (1) upon deprotonation of the (O)P-H fragment. Due to the electron-rich nature, the anionic phosphide oxide unit in 1 takes part in efficient intermolecular hydrogen bonding, which has an unusual and remarkably strong impact on the photoluminescence of 1, changing the emission from red (644 nm) to green-yellow (539 nm) in the solid. The basicity of the R₂(O)P^- group and its affinity for both inter- and intramolecular donor-acceptor interactions allow converting 1 into hydrohalogenated (2, 3) and boronated (4) derivatives, which reveal a gradual hypsochromic shift of luminescence, reaching the wavelength of 489 nm. Systematic variable-temperature analysis of the excited state properties suggests that thermally activated delayed fluorescence is involved in the emission process. The long-lived excited states for 1-4, the energy of which is largely regulated by means of the phosphide oxide unit, are potentially suitable for triplet energy transfer photocatalysis. With the highest T₁ energy among 1-4, complex 4 demonstrates excellent photocatalytic activity in a [2+2] cycloaddition reaction, which has been realized for the first time for silver(I) compounds.

Facile synthesis of air-stable heterobimetallic osmium-silver hydride complexes

The synthesis and characterization of air-stable heterobimetallic Os-Ag hydrides are described. All of the new heterobimetallic Os-Ag hydrides are neutral, and the in situ generated and presynthesized cis-[Os](H)-CC-R units in these frameworks act as organometallic bidentate chelating ligands coordinating with the AgPPh₃ cation, which makes these complexes more stable. Our results provide a new synthetic route for the construction of stable heterobimetallic complexes.

The interesting luminescence behavior and rare nonlinear optical properties of the {Ag55Mo6} nanocluster

The reversible thermochromic luminescence and rare third-order NLO properties of the {Ag55Mo6} nanocluster reported were studied experimentally, and the contributions of Ag+, CC− and MoO42− groups to NLO properties were proved by DFT calculations.

Novel chloride-centered Ag18 clusters featuring a cuboctahedral Ag12 skeleton

Two novel chloride-centered Ag₁₈ clusters with the same framework but different supporting phosphines are synthesized by the reaction of PhC[triple bond, length as m-dash]CAg, AgSbF₆, PPh₃ (or P(p-Tol)₃), and NaBH₄ in CH₂Cl₂, followed by the addition of PhC[triple bond, length as m-dash]CH and NEt₃. The inner twelve Ag atoms of these two clusters are arranged in a rare cuboctahedral structure, which can be rationalized by considering a ligand effect. Through careful analysis, we find that the central chloride arises from a generally ignored but nonetheless existing reaction between CH₂Cl₂ and NEt₃, which is well recognized as the Menshutkin reaction. This research provides insights into the dependence of the cluster structure on the nature of the ligand and into the cluster formation mechanism of the Menshutkin reaction.

Enhanced thermal stability of Cu–silylphosphido complexes via NHC ligation

The thermal stability of the Cu–P(SiMe₃)₂ moiety can be enhanced via N-heterocyclic carbene ligation.

Strong reverse saturable absorptive effect of an ultrathin film containing octacarboxylic cobalt phthalocyanine and polyethylenimine

A novel nanoscopic composite film with alternating layers consisting of anionic octacarboxylic cobalt phthalocyanine [ CoPc ( COONa )8] and cationic polyethylenimine (PEI) has been fabricated by an electrostatic, layer-by-layer, self-assembly technique. UV-vis spectroscopy revealed consecutive regular deposition of CoPc ( COONa )8/ PEI onto a quartz slide. The film's delicate nanostructure was characterized by atomic force microscopy and small angle X-ray diffraction. Third-order nonlinear properties of the film performed using Z-scan measurements with 21 ps laser pulses at the incidence wavelength of 532 nm showed rather strong, nonlinear reverse saturable absorption.

Assembly of Infinite Silver(I) Columns, Chains, and Bridged Aggregates with Supramolecular Synthon Bearing Substituted Phenylethynides

Structural correlation in a series of eight silver(I) complexes bearing substituted phenylethynide ligands was systematically investigated through variation of the position or steric bulk of substituents on the aromatic ring. All coordination frameworks are constructed with the supramolecular synthon Ar--C triple bond C superset Ag(n) (Ar=4-MeC6H4, 3-MeC6H4, 2-MeC6H4, 4-tBuC6H4, 3,5-(CF3)2C6H3; n=4, 5), and the presence of coexisting ligands was found to influence the supramolecular assembly. The role of pi-pi stacking, C--Hpi and Ag-C(aromatic) interactions in stabilizing the coordination networks is also discussed.

Novel μ5-Coordination Modes of Aryl and Alkyl Ethynides and Classification of Metal–Ligand Interactions in Silver(I) Complexes

Novel mu(5)-eta(1),eta(1),eta(1),eta(1),eta(2) and mu(5)-eta(1),eta(1),eta(1),eta(2),eta(2) coordination modes of alkyl and aryl ethynide moieties are found in silver(I) complexes 1-5, and the metal-ligand distances can be classified into sigma, pi and mixed (sigma,pi) types. With the consistent square-pyramidal capping Ag(5) baskets of the ethynide moiety as supramolecular synthons, a series of two- and three-dimensional coordination networks are obtained.

Fabrication of Ultrathin Films with Large Third-Order Nonlinear Optical Properties

An ultrathin composite film containing anionic Ag-His complexes (His: L-Histidine) and oppositely charged BH-PPV was fabricated by means of the electrostatic layer-by-layer self-assembly technique. UV/Vis spectra showed a continuous deposition process of Ag-His complexes and BH-PPV. The film structure was characterized by using small-angle X-ray diffraction, AFM, and SEM. The nonlinear optical properties of the ultrathin film were studied by using the Z-scan technique with a laser duration of 8 ns at a wavelength of 532 nm. The film sample exhibited a strong nonlinear saturated absorption, with an alpha2 value of -3.9 x 10(-5) mW(-1) and a self-defocusing effect with an n2 value of -4.78 x 10 (-12) m2W(-1).