Experimental and theoretical approach of photophysical properties of lanthanum(III) and erbium(III) complexes of tris(methoxymethyl)-5-oxine podant

Excited State Dynamics of Alizarin Red S Nanoparticles in Solution

Alizarin red S is a sulfonated, water-soluble derivative of alizarin. This work presents femtosecond studies of alizarin red S (ARS) nanoparticles in comparison to ARS in aqueous solution and to alizarin in DMSO. The femtosecond studies cover a probing spectral range of 350-750 nm using different excitation wavelengths, taking into account the variation of the absorption spectra with the pH values of the solvent. Stationary absorption spectra show slight differences between solution and nanoparticles. Excitation at 530 nm results in low and noisy responses, therefore, we additionally recorded transient spectra of the nanoparticles at λex = 267 nm. While the results in DMSO are comparable to previous studies in non-aqueous solvents, we report a relatively fast relaxation of 14 ps in [La(OH)2][ARS] nanoparticles in aqueous solution after excitation at 530 nm, which is similar to Na(ARS) solution (19 ps). The dynamics changed with lower pH, but still without significant differences between nanoparticles and solution. We propose [La(OH)2][ARS] nanoparticles as a suitable alternative to dissolved molecules with similar spectroscopic properties, for example, with regard to biomarker applications.

Spectroscopic, photophysical, solution thermodynamics and computational study of europium and terbium complexes with a flexible quinolinol-based symmetric tripodal chelator

Coordination behaviour and photonic properties of a flexible tripodal multidentate ligand, 5,5',5''-(Cyclohexane-1,3,5-triyltris(oxy))tris(methylene)triquinolin-8-ol (CYTOM5OX), with Eu and Tb ions were explored through potentiometric, UV-visible and fluorescence spectrophotometric methods. The interaction of tripod towards the lanthanides has been examined for thermodynamic equilibrium, photophysical behavior, and time-resolved luminescence measurements. Besides, a theoretically empirical method followed by quantum mechanical treatment of these chelates has also been summarized. A noticeable change in the electronic spectra of these complexes disclose CYTOM5OX as a pH-sensitive optical sensor for lanthanides detection; also, a strong green fluorescence allows simultaneous sensing in the visible region in a competitive medium. The intense fluorescence intermittently gets quenched under acidic and basic conditions due to photoinduced intramolecular electron transfer from the excited 8-hydroxyquinoline (8-HQ) moiety to the metal ion. The thermodynamically stable Ln³⁺ complexes in aqueous solution show stability constants in the range log β₁₁₀ = 33-35 and pLn³⁺ in the range of 21-22. The hydration number that was predicted by the coordination scan was substantiated by lifetime measurements reveal presence of coordinated water molecules in Eu(CYTOM5OX) and Tb(CYTOM5OX) complexes. Theoretical spectra were also calculated by ZINDO/s methodology at single excitations (CIS) level on PM7 as sparkle energy-minimized geometries.

Photoluminescence and Coordination Behaviour of Lanthanide Complexes of Tris (Aminomethyl)Ethane-5-Oxine in Aqueous Solution

Photophysical properties of a multidentate tripodal ligand, 5,5'-(2-(((8-hydroxyquinolin-5-yl) methylamino)methyl)-2-methylpropane-1,3-diyl) bis (azanediyl)bis (methylene)diquinolin-8-ol, (TAME5OX), with La³⁺ and Er³⁺ ions have been examined for photonics applications. The change in behavior in electronic spectra of these complexes reveals the use of TAME5OX as a sensitive optical pH based sensor to detect Ln³⁺ ions whereas indication of strong green fluorescence allows simultaneous sensing within the visible region in competitive medium. The intense fluorescence intermittently gets quenched under acidic and basic conditions due to photoinduced intramolecular electron transfer from the excited 8-hydroxyquinoline (8-HQ) moiety to the metal ion. This renders these compounds the OFF-ON-OFF type of pH-dependent fluorescent sensor. The thermodynamic stability and coordination behaviour of the chelator with the said lanthanide ions have also been probed by potentiometric, UV - visible and fluorescence spectrophotometric method. TAME5OX forms protonated complex [Ln (H₄L)]⁴⁺ below pH ~4.0 which sequentially deprotonates through one proton process with increase of pH. The stability constants of neutral complexes have been determined to be in the range log β₁₁₀ = 32-34 and pLn in the range of 14-20, indicating TAME5OX is a good synthetic lanthanide chelator. Theoretical spectra were also calculated by ZINDO/s methodology at single excitations (CIS) level on PM7 as sparkle energy-minimized geometries.

Thiosemicarbazide chemical functionalized carbon dots as a fluorescent nanosensor for sensing Cu2+and intracellular imaging

Synthesis procedures for the CDs-based nanosensor and schematic diagram of Cu²⁺detection.

RM1 Semiempirical Quantum Chemistry: Parameters for Trivalent Lanthanum, Cerium and Praseodymium

The RM1 model for the lanthanides is parameterized for complexes of the trications of lanthanum, cerium, and praseodymium. The semiempirical quantum chemical model core stands for the [Xe]4fn electronic configuration, with n =0,1,2 for La(III), Ce(III), and Pr(III), respectively. In addition, the valence shell is described by three electrons in a set of 5d, 6s, and 6p orbitals. Results indicate that the present model is more accurate than the previous sparkle models, although these are still very good methods provided the ligands only possess oxygen or nitrogen atoms directly coordinated to the lanthanide ion. For all other different types of coordination, the present RM1 model for the lanthanides is much superior and must definitely be used. Overall, the accuracy of the model is of the order of 0.07Å for La(III) and Pr(III), and 0.08Å for Ce(III) for lanthanide-ligand atom distances which lie mostly around the 2.3Å to 2.6Å interval, implying an error around 3% only.

TAME5OX, abiotic siderophore analogue to enterobactin involving 8-hydroxyquinoline subunits: thermodynamic and photophysical studies

The synthesis, thermodynamic and photophysical properties of trivalent metal complexes of biomimetic nonadentate analogue, 5,5'-(2-(((8-hydroxyquinolin-5-yl)methylamino)methyl)-2-methylpropane-1,3-diyl)bis(azanediyl)bis(methylene)diquinolin-8-ol (TAME5OX), have been described. Combination of absorption and emission spectrophotometry, potentiometry, electrospray mass spectrometry, IR, and theoretical investigation were used to fully characterize metal (Fe(+3), Al(+3) and Cr(+3)) chelates of TAME5OX. In solution, TAME5OX forms protonated complexes [M(H3L)](3+) below pH 3.4, which consecutively deprotonates through one to three-proton processes with rise of pH. The formation constants (Logβ11n) of neutral complexes formed at or above physiological pH, have been determined to be 30.18, 23.27 and 22.02 with pM values of 31.16, 18.07 and 18.12 for Fe(+3), Al(+3) and Cr(+3) ions, respectively, calculated at pH 7.4, indicating TAME5OX is a powerful among synthetic metal chelator. The results clearly demonstrate that the ligand in a tripodal orchestration firmly binds these ions over wide pH range and forms distorted octahedral complexes. The binding and the coordination event could be monitored from absorption and fluorescence spectroscopy. The high thermodynamic stability in water at physiological pH of ferric complex of TAME5OX indicates that these complexes are resistant to hydrolysis and therefore are well suited for the development of device for applications as probes. The ligand displays high sensitive fluorescence enhancement to Al(3+) at pH 7.4, in water. Moreover, TAME5OX can distinguish Al(3+) from Fe(3+) and Cr(3+) via two different sensing mechanisms: photoinduced electron transfer (PET) for Al(3+) and internal charge transfer (ICT) for Fe(3+) and Cr(3+). Density functional theory was employed for optimization and evaluation of vibrational modes, NBO analysis, excitation and emission properties of the different species of metal complexes observed by solution studies.

Design, synthesis and photophysical properties of 8-hydroxyquinoline-functionalized tripodal molecular switch as a highly selective sequential pH sensor in aqueous solution

TAME5OX can act as a good candidate with potential applications in chemical and biological fields. Fluorescence reduction due to ESIPT between protonated NH⁺ ∼ –OH and deprotonated N ∼ –O⁻ forms was proven by DFT calculation.