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The molecular and crystal structure of boron difluoride acetylacetonates containing selenophenyl (1), diselenide (2) and selenocyanate groups (3) at the central carbon atom (γ) has been determined. As a result of comparing the structure of selenium- and sulfur-substituted complexes, it is shown that the replacement of a sulfur atom with a selenium atom practically does not change the relative position of substituents and chelate cycles, as well as the values of the main angles. The packing of complexes 2 and 3 in crystals repeats the packing of sulfur-containing analogues. For phenyl-substituted selenide and sulfide, the crystals are not isostructural. In the diselenide complex 2 molecules crystallize in pairs with one chelate cycle of each molecule participating in pair formation. The pairs are linked by an interaction similar to the stacking interaction. The second chelate cycle of each molecule in the pair does not participate in intermolecular interactions. In the acetylacetonate complexes studied, the chelate rings are not planar. These cycles have a "boat" conformation. The magnitude of bending of the cycle is determined by intermolecular interactions. [ABSTRACT FROM AUTHOR]

The nature of excited states of 2-β-diketonato-1,3,2-benzodioxaborol compounds with aromatic substituent have been studied by the quantum-chemical method in the approximation of the time-dependent electron density functional theory. We have measured the absorption spectra of these compounds in acetonitrile solution and compared them with the model spectra constructed on the basis of calculations. The calculations give two long-wavelength transitions with small oscillator strengths, caused by π-π transitions with the charge transfer from the benzodioxo-group to the chelate fragment. Observed long-wavelength shoulders of the spectra bands correlate with the mentioned transitions. Typical high intensity bands for π-π transitions in the ultra-violet range are caused by transitions of π-electrons in the fragments. Increasing extension of π-system gives the batochromic shift of these absorption bands and the growth of the probabilities of the transition., (Copyright © 2015 Elsevier B.V. All rights reserved.)