Zinc(II) bis(dipyrromethenate)s crystal solvates with dimethyl sulfoxide Composition, stability and spectral-luminescent properties

Abstract It was found that 3,3′-, 2,3′ and 2,2′-zinc(II) bis(dipyrromethenate)s ([Zn 2 L 2 ]) form stable supramolecular complexes of the composition [Zn 2 L 2 (DMSO) n ] (n = 1 or 2) with dimethyl sulfoxide (DMSO). The [Zn 2 L 2 (DMSO) n ] are stable in the solid phase and solutions. Composition, stability, and spectral-luminescent properties of the [Zn 2 L 2 (DMSO) n ] crystal solvates were studied by means of FTIR, PXRD, 1 H NMR, DOSY, absorption and fluorescence analyses. Spectroscopic studies showed that the quantum yields ( φ ) of [Zn 2 L 2 (DMSO) n ] are lower (to ∼1.6–3.6 times) than quantum yields ( φ о ) of [Zn 2 L 2 ] in cyclohexane. Quantum-chemical study allowed to suggest the most likely mechanism of the DMSO molecules coordination on the coordinating centers of [Zn 2 L 2 ]. It is demonstrated, that the high-energy coordination interactions (Zn − O) in [Zn 2 L 2 (DMSO) n ] are the main cause of the fluorescence quenching of [Zn 2 L 2 ] in the presence of DMSO. Fluorescence quenching of [Zn 2 L 2 ] in the DMSO presence is based on the photoinduced electron transfer (PeT) mechanism. The obtained results are interesting for the development of new [Zn 2 L 2 ] fluorescent sensors of the DMSO molecules.