Synthesis of new bis-bidendate N/O spiro-bino-spiro-cyclotriphosphazenes: Structural investigations and DFT studies

Abstract

The Schiff bases 4,4'-di(2-hydroxybenzyl imino) diphenylmethane (S1), 4,4'-di(2-hydroxy-5-chloro benzyl imino) diphenylmethane (S2) and 4,4'-di(2-hydroxy-5-bromo benzyl imino) diphenylmethane (S3) were synthesized from the condensation reactions of salicyl-aldehyde, 5-chlorosalicylaldehyde and 5-bromosalicylaldehyde, respectively, with 4,4-diaminodiphenylmethane and reduced with NaBH4 in dry MeOH to obtain N/O-donor type ligands 4,4'-di(2-hydroxy benzyl amino) diphenylmethane (L1), 4,4'-di(2-hydroxy-5-chloro benzyl amino) diphenylmethane (L2) and 4,4'-di(2-hydroxy-5-bromo benzyl amino) diphenylmethane (L3). The novel spiro-bino-spiro-cyclotriphosphazene derivatives 1 - 3 were obtained from the reactions of L1-L3 with trimer (N3P3Cl6). The identities of these compounds were elucidated by P-31-, H-1-, C-13-NMR, FT-IR spectroscopy and elemental analysis. The solid state structures of compounds 1 and 2 were determined by single crystal X-ray diffraction. Experimental results on the molecular structures of compounds 1 and 2 were supported by computational studies using Density Functional Theory (DFT) methods with Becke-3-Lee-Yang-Parr (B3LYP) functional and 6-31+G(2d,p) basis set. The experimentally determined values of the bond angles and bond lengths in the compounds are in accord with to those predicted theoretically.