M. V. Puzyk

The effect of acids on fluorescence of coumarin-6 in organic solvents

The effect of acids (HCl, HClO4, HNO3, and CH3COOH) on the fluorescence of coumarin-6 in organic solvents (acetonitrile, acetone, butanol-1, and ethanol) is studied. The regions of acid (HCl, HClO4, HNO3) concentrations that lead to a change in the fluorescence spectra are determined for each of the solvents. It is shown that, for all the solvents studied, acetic acid with a concentration within the region 10−1–10−6 M causes no significant changes in the fluorescence spectrum of coumarin-6. A mechanism of the coumarin-6 protonation is proposed.

Spectral and Luminescent Properties of Ammonia Cyclopalladated Complexes

The synthesis of ammonia cyclometalated palladium(II) complexes [Pd(NH3)2C^N]ClO4 (C^N is the deprotonated form of 2-phenylpyridine, 2-(para-tolyl)pyridine, 7,8-benzo(h)quinoline, 2,6-diphenylpyridine, and 4-phenylpyrimidine) is developed. The IR and electronic absorption and emission spectra of these complexes are studied. It is found that the ammine and analogous ethylenediamine cyclometalated Pd(II) complexes have similar spectral and luminescent properties and the same nature of the electronically excited 3(π-π*)-type state responsible for the long-lived luminescence, the π and π* orbitals being localized on the corresponding cyclometalating ligand. The efficient temperature quenching of the luminescence of Pd(II) complexes at room temperature is assigned to the thermally activated population of metal-centered electronically excited states with subsequent nonradiative deactivation.

Spectral and luminescent investigations of ammonia cyclometalated Pt(II) complexes

A method of synthesis of ammonia cyclometalated Pt(II) complexes [Pt(NH3)2C∧N]ClO4, where C∧N is 2-phenylpyridinate or 2-phenylbenzothiazole ion, is developed. The electronic absorption and emission properties of the complexes are studied. It is found that the state responsible for intense long-lived luminescence is the excited charge-transfer state of the 3(d-π*) type, the π* orbital being localized at the corresponding cyclometalating ligand. Formation of platinum blue is observed in air-saturated aqueous solutions of ammonia cyclometalated complexes.

Optical properties of cyclometalated Pd(II) and Rh(III) complexes based on 2-(4-biphenylyl)-6-phenylbenzoxazole luminophore with ethylenediamine

Using the methods of electronic absorption and emission spectroscopy, we have studied the optical properties of cyclometalated [Pd(C∧N)En]CH3COO and [Rh(C∧N)2En]Cl complexes of 2-(4-biphenylyl)-6-phenylbenzoxazole luminophore with ethylenediamine. We have shown that, along with a bathochromic shift of intraligand spin-allowed π-π* optical transitions by 1000–1800 cm−1, complexes are characterized by the occurrence of long-wavelength bands of a mixed nature (intraligand-metal-ligand charge transfer) in the range of 369—392 nm and by competing intraligand fluorescence (419–423 nm) and phosphorescence (511–532 nm) processes under low-temperature (77 K) photoexcitation.

Spectroscopic properties of 2-phenylbenzothiazole and 1-phenylpyrazole luminophores metalated with platinum metals

The effect of metalation of 2-phenylbenzothiazole and 1-phenylpyrazole with Pd(II), Pt(II), and Rh(III) on the structure and optical properties of luminophore complexes is studied by 1H NMR spectroscopy, IR spectroscopy, and electronic absorption and emission spectroscopy. It is shown that metalation of luminophores leads to the formation of five-membered {M(C∧N)} fragments in the composition of square planar and octahedral complexes, which exhibit a long-wavelength charge-transfer band. The luminescence properties of the complexes are characterized by quenching of the fluorescence and by enhancement of the phosphorescence from the mainly intraligand excited state. Fluorescence quenching of complexes is attributed to the thermally activated energy transfer to metal-centered states and their efficient nonradiative decay.

The influence of perchloric acid on spectral and luminescent characteristics of 4-phenylpyrimidine and 1,7-phenanthroline

The influence of perchloric acid on the spectral and luminescent characteristics of 4-phenylpyrimidine and 1,7-phenanthroline is studied. Stepwise protonation of both nitrogen atoms is established.

Spectral and Luminescent Properties of N-(3-Methoxysalicylidene)-o-anisidine and Its Zinc Complex

The synthesis and the spectral and luminescent properties of N-(3-methoxysalicylidene)-o-anisidine and its Zn(II) complex are presented. It is found that Schiff base in solution has the E(anti)-configuration, and the zinc complex fluoresces in solution and the polycrystalline state at 77 and 293 K.

The influence of perchloric acid on the spectral and luminescent properties of cyclopalladated complexes

The influence of perchloric acid in ethanol on the spectral and luminescent characteristics of cyclopalladated amine complexes with 4-phenylpyrimidine, 1,7-phenanthroline, and coumarin-6 is studied. A protonation mechanism is proposed.

The change of the spectral-luminescent properties of coumarin-7 and coumarin-30 upon protonation

The influence of perchloric acid on the spectral-luminescent characteristics of coumarin-7 and coumarin-30 in acetonitrile and ethanol is studied. A probable mechanism and methods of controlling the protonation of nitrogen atoms of the phenylimidazole fragment are discussed.

Azobenzene Pd(II) complexes with N^N- and N^O-type ligands

Methods of synthesis of cyclometalated azobenzene palladium(II) complexes of [Pd(N^N)Azb]ClO4 and [Pd(N^O)Azb]ClO4 types (where Azb– is the deprotonated form of azobenzene; N^N is 2NH3, ethylenediamine, or 2,2′-bipyridine; and (N^O)– is the deprotonated form of amino acid (glycine, α-alanine, β-alanine, tyrosine, or tryptophan)) are developed. The electronic absorption and the electrochemical properties of these complexes are studied.