Anomalous Temperature Dependence of the ¹²⁷I-Quadrupole Coupling in (C₆H₅)₄PIO₄, (C₆H₅)₄AsIO₄ and (C₆H₅)₄SbIO₄

Abstract

On measuring second order quadrupole effects in 127I solid state NMR, new anomalous temperature coefficients of the quadrupole interaction were observed in tetraphenylphosphonium-, tetraphenylarsonium- and tetraphenylstibonium metaperiodate. The relevance of possible mechanisms like breakdown of dπ - pπ backbonding, negative pressure coefficients, charge transfer, orientational change of the electric field gradient tensors, and influence of reorientational motions is discussed for these compounds.