Antifreezing Effect of the Central Metal on Porphyrin Supercooled Liquid and Glass

Theantifreezing effect of the central metal on porphyrinsupercooled liquid and glass is explored. The central metal enhancesthe intermolecular interactions of the porphyrin segments, increasesthe viscosity, and thus reduces the probability of nucleation andslows crystallization. The profound impact of the central metal on the morphologicalpropertiesof metalloporphyrins bearing 3,4,5-tri((S)-dihydrocitronellyloxy)phenylgroups at the diagonal meso-positions is disclosed.Systematic comparison of the free-base porphyrin 1H ( 2 ) with metalloporphyrins 1Ms incorporatingNi(II), Cu(II), and Zn(II) as the central metal found the counterintuitiveantifreezing effect of the central metal; 1H ( 2 ) crystallizes immediately after the removal of thesolvent, while the central metal retards nucleation. We interpretthat the miscibility of the elastic alkyl chains and the porphyrinsegment is crucial in imparting fluidity to 1M and smoothnucleation in the context of classical nucleation theory, while thefull rationalization of the thermal behaviors requires the existenceof the nuclei precursor according to the two-step nucleation model.The morphological behaviors of 1Ms are highly susceptibleto only marginal differences in the chemical structure, presumablydue to the relatively large discrete size of the porphyrin ring, approximately1 nm. The somewhat counterintuitive antifreezing effect of the centralmetal is interpreted to arise from the increased viscosity due tothe enhanced molecular interactions.

Automated summary

The antifreezing effect of central metal on porphyrin supercooled liquid and glass is investigated. The central metal enhances intermolecular interactions, increases viscosity, and slows crystallization process. The impact of the central metal on metalloporphyrins with specific chemical structures is discussed.