ABSTRACT
Redox-active proanions of the type B12(OCH2Ar)12 [Ar = C6F5 (1), 4-CF3C6H4 (2), 3,5-(CF3)2C6H3 (3)] are introduced in the context of an experimental and computational study of the visible-light-initiated polymerization of a family of styrenes. Neutral, air-stable proanions 1-3 were found to initiate styrene polymerization through single-electron oxidation under blue-light irradiation, resulting in polymers with number-average molecular weights (Mn) ranging from â¼6 to 100 kDa. Shorter polymer products were observed in the majority of experiments, except in the case of monomers containing 4-X (X = F, Cl, Br) substituents on the styrene monomer when polymerized in the presence of 1 in CH2Cl2. Only under these specific conditions are longer polymers (>100 kDa) observed, strongly supporting the formulation that reaction conditions significantly modulate the degree of ion pairing between the dodecaborate anion and cationic chain end. This also suggests that 1-3 behave as weakly coordinating anions (WCA) upon one-electron reduction because no incorporation of the cluster-based photoinitiators is observed in the polymeric products analyzed. Overall, this work is a conceptual realization of a single reagent that can serve as a strong photooxidant, subsequently forming a WCA.
ABSTRACT
We report a new class of redox-active vertex-differentiated dodecaborate clusters featuring pentafluoroaryl groups. These [B12(OR)11NO2] clusters share several unique photophysical properties with their [B12(OR)12] analogues, while exhibiting significantly higher (+0.5 V) redox potentials. This work describes the synthesis, characterization, and isolation of [B12(O-CH2C6F5)11NO2] clusters in all 3 oxidation states (dianion, radical, and neutral). Reactivity to post-functionalization with thiol species via SNAr on the pentafluoroaryl groups is also demonstrated.
