AN OPTICAL BASICITY STUDY OF METAL CARBOXYLATE GLASSES AT AMBIENT ANDELEVATED-TEMPERATURES

Molten mixtures of metal carboxylates, especially those of the alkali and alkaline earths, can be quenched to form stable glasses which can act as hosts for a wide range of organic, organometallic and inorganic substances, and since the interaction with these often involves the g lass behaving as a Lewis base, this property has been determined quant itatively as the optical basicity, LAMBDA. The measurement uses the ul traviolet S-1(0) --> P-3(1) absorption of s2 p-block ions such as Pb2, and this was possible because the carboxylate glasses have ultraviol et transparency extending to approximately 44000 cm-1 (approximately 2 30 nm). The LAMBDA values of the glasses increase with increasing basi city of the parent metal oxide (e.g. Na2O, CaO) in accordance with the optical basicity principle which operates for inorganic glasses. This allows assignment of a LAMBDA value to acetic anhydride (0.47) which is close to that for SiO2 (0.48). The effect of chain length of the ca rboxylate anion on LAMBDA was shown to be slight. For the heated glass es, there was evidence for the presence of sites of higher basicity. T he existence of two types of oxygen, analogous to bridging and nonbrid ging in conventional glasses, is discussed in terms of polarisabilitie s derived from refractivity data.