Supramolecular Control of Magnetism and Morphology of Hybrid Diblock Copolypeptide Amphiphile/Cyanide-Bridged Molecular Square Complexes

Manystudies have investigated the self-assembly capabilities ofdiblock copolypeptide amphiphiles, with a specific focus on theirpotential to form various nanostructures. In addition, significantattention has been drawn to the integration and alignment of spintransition complexes with such amphiphiles, driven by the potentialof these materials to exhibit molecular spintronics. Building uponthese concepts, the present work explores the construction of supramolecularhybrids involving a cyanide-bridged Fe-Co molecular square complexand diblock copolypeptide amphiphiles in aqueous solutions. Specifically,the crystalline [Co2Fe2(CN)(6)(tp*)(2)(dtbbpy)(4)](2+) complex (tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borateand dtbbpy = 4,4 & PRIME;-di-tert-butyl-2,2 & PRIME;-bipyridine)has been previously reported to exhibit a two-step electron-transfer-coupledspin transition phenomenon. The integration of such spin transitioncomplexes with diblock copolypeptide amphiphiles in aqueous environmentsholds promising potential for the development of advanced materialsin molecular spintronics, and this study aims to shed light on thesupramolecular characteristics and behavior of these intriguing hybridsystems. In this study, the addition of poly-(l-aspartate)-block-(l-leucine) amphiphiles to solutions of thiscomplex induced the formation of supramolecular assemblies such asnanosheets, resulting in controllable two-step spin crossover originatingfrom tetranuclear complexes undergoing intermolecular interactions.Characterizations using electron microscopy and spectroscopic techniquesconfirmed the formation of nanosheets with weave patterns severalnanometers in size that grew to form advanced nanosheet architectures,including sheeted backbone structures having & beta;-sheet conformations.This concept of combining diblock copolypeptide amphiphiles with adiscrete spin crossover complex is expected to allow the design offlexible, functional supramolecular hybrid spin systems in water.