Thermal and spectroscopic characterization of zinc(II) bis(dipyrrinate)s crystal solvates with acetone, dimethyl sulfoxide, and triethylamine

Abstract

The crystal solvates of 2,2′-, 2,3′- and 3,3′-bis(dipyrrinato)zinc(II) with acetone, dimethyl sulfoxide, and triethylamine were obtained by slow crystallization. Composition, stability, and spectral luminescent properties of the samples were studied. Spectroscopic studies showed that the quantum yield (φ) of crystal solvates in cyclohexane is noticeably lower (to ~1.5–4.5 times) than φ for of [Zn2 L 2] helicates. The thermal dissociation processes of crystal solvates in an argon atmosphere have been investigated. It is shown that bis(dipyrrinato)zinc(II) form stable supramolecular complexes with electron donor molecules X of the composition [Zn2 L 2Xn], where n = 1, 2, or 4. Crystal solvates are stable up to a temperature ~356.9–412.2 К. The energy stability of the solvates [Zn2 L 2Xn] reduced at replacing the 2,2′-bis(dipyrrine) on 2,3′- and 3,3′-isomer and with a decrease in electron donor number of molecular ligands X: Acet, DMSO, TEA. It is demonstrated that the high energies of the coordination interactions Zn–X in supramolecular complexes [Zn2 L 2Xn] are the main cause of the fluorescence quenching of [Zn2 L 2] luminophores in the presence of electron donor ligands X. The obtained results are of interest for the development on the basis of [Zn2 L 2] of the new fluorescent sensors of the electron donor molecules.