TRIMETHYL PHOSPHATE-BENZENE COMPLEX - A MATRIX-ISOLATION INFRARED STUDY AND SEMIEMPIRICAL (AM1) COMPUTATIONS

A 1 : 1 molecular complex of trimethyl phosphate (TMP) and benzene tra pped in solid nitrogen and argon was studied using matrix isolation in frared spectroscopy. The formation of the complex was evidenced by a a pproximate to 5 cm(-1) red-shift in the P=O stretching frequency of th e TMP sub-molecule in the complex. Peak profile of the upsilon(4) out- of-plane bending fundamental of C6H6 was also found to be perturbed in the complex. Semiempirical calculations using the AMI hamiltonian, in dicated that TMP interacts with C6H6 through a hydrogen bond formation between the phosphoryl oxygen and one of the hydrogens in benzene. Th e stabilization energy of this complex was approximate to 7 kJ/mol. Th is work therefore reports the study of a weak hydrogen bonded complex involving a hydrogen attached to carbon, which in recent times has com e to be recognized as important in biological systems and crystal engi neering. (C) 1998 Elsevier Science B.V.