Porphyrin-based metal coordination polymers with self-assembly pathway-dependent properties for photodynamic and photothermal therapy

Porphyrin-based metal coordination polymers (MCPs) have attracted numerous attention due to their great promise application in phototherapy including photodynamic therapy (PDT) and photothermal therapy (PTT). However, the detailed self-assembly process of porphyrin-based MCPs still remains poorly understood. This work provides a detailed study of the self-assembly process of MCPs constructed by Mn2+ and TCPP (TCPP: 4,4′,4′′,4′′′-(Porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid)) in aqueous solution. Unlike traditional nucleation and growth mechanism, we discover that there is a metastable metal-organic intermediate which is kinetically favored in the self-assembly process. And the metastable metal-organic intermediate nanotape structures could convert into thermodynamically favored nanosheets through disassembling into monomers followed by reassembling process. Moreover, the two structurally different assemblies exhibit distinct photophysical performances. The intermediate Mn-TCPP aggregates show good light-induced singlet oxygen 1O2 generation for PDT while the thermodynamic favored stable Mn-TCPP aggregates exhibit good photothermal conversion ability as photothermal agents (PTAs). This study could facilitate controlling self-assembly pathway to fabricate complex MCPs with desirable applications.