Kinetically controlled self-assembly of phthalocyanine-peptide conjugate nanofibrils enabling superlarge redshifted absorption

Abstract

Supramolecular assembly could in principle lead to redshifted absorption through J-aggregation of chromophores, which would be a highly promising method for achieving near-infrared materials with improved functionality and flexibility. To effectively enhance the material functionalities, one of the great challenges remaining is to achieve an aggregation state with a redshift larger than 100 nm. Conventional assemblies that are mostly thermodynamically controlled have a limited redshifted absorption of less than 30 nm. In this work, using a model phthalocyanine- peptide conjugate compound, we achieved the first fabrication of phthalocyanine-based near-infrared materials with a superlarge absorption redshift of 105 nm by a kinetically controlled self-assembly strategy. In this kinetically controlled self-assembly process, sufficient rearrangement of intermolecular aggregates to an ordered structure is revealed to be crucial to facilitate the formation of nanofibrils instead of nanoparticles, which are formed via a general rapid self-assembly pathway under thermodynamic control. The superlarge redshift in the absorbance of assembled nanofibrils originates from the orderly stacked phthalocyanine chromophores, which enable a charge transfer state through more effective intermolecular orbital overlapping. The kinetically controlled J-aggregation state of the phthalocyanine-peptide conjugate with superlarge redshifted absorption not only opens an unprecedented route toward novel near-infrared phthalocyanine materials but also holds great promise for revealing general design principles for various organic dye materials.