Self-assembly of a new class of rhenium(i)-based double stranded dinuclear monohelicates with their photophysical and electrochemical studies

A new class of double stranded dinuclear monohelicates, fac-[{Re(CO)(3)-(mu-L)-Re(CO)(3)}L-n] (1-4), were self-assembled from Re-2(CO)(10), a rigid bischelating donor (H-2-L: 1,4-dihydroxybenzoquinone (H-2-dhbq) for 1 and 3; 2,5-pyrazine dicarboxylic acid (H-2-pydc) for 2 and 4) and a flexible bis(monodentate) pyrazolyl N donor L-n (L-1 = bis(4-((pyrazolyl)methyl)phenyl)methane for 1 and 2; L-2 = bis(4-((pyrazolyl)methyl)phenyl)methanone for 3 and 4) in mesitylene. Metallomacrocycle 1 was confirmed by single crystal X-ray crystallography. Although these helicates contain two organic ligand strands, only one strand is arranged in a helical fashion, which is an unprecedented form in the helicate architecture. The molecular structures of 1-4 as helicates and mesocates were optimized using DFT methods. The dynamic interconversion of the metallomacrocycles in solution was studied by H-1 NMR studies. The photophysical properties of 1-4 were studied experimentally and the nature of electronic transitions was determined by TD-DFT analysis. Quinonoid motif-based complexes 1 and 3 displayed strong visible light absorption. The redox properties of 1-4 were studied using cyclic voltammetry.

Automated summary

This article reports a new class of double stranded dinuclear monohelicates and describes their self-assembly, structure optimization, dynamic interconversion in solution, and studies on their photophysical and redox properties.