The influence of structural factors on the composition, spectral-luminescent properties and thermal stability of zinc(II) bis(dipyrromethenate)s crystal solvates with aromatic hydrocarbons

Publication date: July 2017
Source:Journal of Luminescence, Volume 187
Author(s): Alexander A. Ksenofontov, Galina B. Guseva, Elena V. Antinа
It was found that methylsubstituted zinc(II) bis(dipyrromethenate)s ([Zn2L2]) form stable supramolecular π-π-complexes [Zn2L2Xn] (n=1, or 2) with aromatic hydrocarbons (Х) (X - benzene (B), toluene (T), m-xylene (mX), p-xylene (pX), and o-xylene (oX)). The [Zn2L2Xn] solid samples were obtained by the slow crystallization from the [Zn2L2] saturated solutions in X at the temperature about 300K. Composition, stability, and spectral-luminescent properties of the [Zn2L2Xn] crystal solvates were studied by means of FT-IR, PXRD, thermal, mass spectral, quantum chemical, absorption, and fluorescence analyses. Spectroscopic studies showed that the quantum yields (φ) of [Zn2L2Хn] are lower (to ~1.2–3.9 times) than quantum yields (φо) of [Zn2L2] in cyclohexane. It was shown that fluorescence quenching efficiencies of helicates increase with decreasing the molecular ligands aromaticity. The thermal dissociation processes of [Zn2L2Xn] have been investigated in argon atmosphere. Crystal solvates are stable up to the temperature ~369–477K. The [Zn2L2Xn] solvates stabilities increase with decreasing the number of alkyl substituents in pyrrole rings of complex domains. It was demonstrated that high values of energy of π-π-intermolecular interactions in [Zn2L2Xn] are the main cause of the fluorescence quenching of [Zn2L2] in the aromatic hydrocarbons presence.

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