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The results of combined experimental and theoretical investigations of the spectral behavior of anil-type systems are presented. Two species: N-triphenylmethylsalicylidene imine (MS1) and N-salicylidene methylamine (SmA) were studied. The electronic (absorption, emission and excitation) spectra of MS1 at room temperature were investigated in pure isooctane as well as in acetonitrile and methanol solutions by the steady-state experiments. A mechanism of molecular processes in the ground and excited states in different microenvironments is also proposed. It includes formation of intra- and intermolecular hydrogen bonds, their role in stabilization of molecular conformations and conformation equilibria. The "solvent assisted" proton transfer reaction and rearrangement were modeled using complexes obtained by attaching methanol molecules to the species studied. The OH-rotamer of SmA was also considered. Infrared and Raman spectra were predicted for MS1 and SmA and compared with the experimental data. An analysis of fundamental vibration frequencies was carried out. Quantum chemical ab initio calculations at the HF/6-31G** level were performed for the species studied and their complexes. Chemical formula of anil-type compound: N-salicylidene methylamine (SmA), N-salicylideneaniline (SA) and N-triphenylmethylsalicylidene imine (MS1). [Structure: see text].

Excited state relaxation of N-(triphenylmethyl)-salicylidenimine (MS1) in protic and aprotic solvents has been investigated by means of absorption pump-probe spectroscopy with femtosecond time resolution and fluorescence spectroscopy with picosecond time resolution. Short-lived excited states and long-lived photoproducts have been identified from the differential absorption spectra. Excited states and photoproducts were different under excitation of enol-closed and cis-keto tautomers. As a result, the commonly accepted excited state relaxation model of aromatic anils, which assumes an ultrafast transformation of excited enol-closed tautomers into cis-keto tautomers, has been modified. Performed quantum chemical calculations suggest that hydrogen-bonded ethanol molecules facilitate formation of cis-keto tautomers and are responsible for their different relaxation pathways in comparison with relaxation of excited enol-closed tauromers. Fluorescence decay on a nanosecond time scale was attributed to aggregated MS1 molecules.

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