Synthesis and photophysical properties of Cd(II) and Cu(II) complexes with decamethylated bis(dipyrrolylmethene)

Copper(II) and cadmium(II) complexes with bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)-methane were synthesized. Influence of the complex-forming ion nature on the optical properties of [Cd₂L₂] and [Cu₂L₂] helicates was studied.     

Coordination reactions of 3,3′-bis(dipyrrolylmethene) with Co(II), Cu(II), and Zn(II) acetylacetonates, valinates, and dipyrrolylmethenates

Using spectrophotometry we found that ligand exchange in the systems of H₂L-[MX₂]-DMF, where M denotes Co²⁺, Cu²⁺, and Zn²⁺; X means Acac^?, Val^?, dpm^?; Hdpm^? is hexamethyldipyrrolylmethene, H₂L is bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)methane, proceeds through successive stages of formation of hetero- and homoleptic binuclear complexes. Conventional sensitivity of the spectrophotometric determination of Co²⁺, Cu²⁺, and Zn²⁺ reaches 10^?9 M.     

Synthesis and spectral analysis of alkyl-substituted 3,3′-bis(dipyrrolylmethenes)

Four new alkyl-substituted 3,3′-bis(dipyrrolylmethene) dihydrobromides containing from 4 to 10 alkyl substituents were synthesized. In a highly alkylated ligand of these substances one of the hydrogen atoms of the 3,3′-methylene spacer was substituted with a phenyl group. The compounds obtained were studied by IR, ¹H NMR, electron absorption, and fluorescent spectroscopy. The increased alkylation degree of pyrroles and the introduction of an aryl substituent in the 3,3′-spacer causes a significant high-frequency shift of the N-H stretching vibrations in the IR spectra, an upfield shift of the NH-proton signals in 1H NMR spectra, a decrease in the auxochromic effects of protons on the aromatic system of chromophore in the composition of salts. The red shift of maximum of the strong band in electron absorption spectra and the emission spectra of compounds in DMF, DMSO, C₅H₅N, C₆H₆, and CHCl₃ was established. The salts obtained are stable in benzene and chloroform, while in electron-donor solvents the irreversible processes of solvolytic dissociation of salts to free organic base and HBr take place.     

Thermal properties of ligands, salts and metal complexes of linear oligopyrroles

The effect of structure on the thermal properties of dipyrrolylmethanes, dipyrrolylmethenes, bis (dipyrrolylmethenes), their salts, and chelates is analyzed proceeding from the results of thermogravimetric analysis. The common tendency is a decrease in the thermal stability of compounds with a disturbed symmetry of alkyl substitution of ligands and with a higher degree of their alkylation, with the increased size of alkyl substituents, with the nitrogen atom in the five-member cycles replaced by S or O. The opposite effect occurs at the change in the mode of attaching methylene spacer in going from 2,2′- to 3,3′-bis(dipyrrolylmethenes). The effects of the themostabilization of the ligands of linear oligopyrroles in the composition of chelates and HBr salts are evaluated quantitatively.