[60]Fullerene Complexes with Supramolecular Zinc Tetraphenylporphyrin Assemblies: Synthesis, Crystal Structures, and Optical Properties

Abstract

Different mono-, bi-, and tetradentate N- and O-containing ligands (L) were used in the design of monomer, dimer, and pentamer zinc tetraphenylporphyrin (ZnTPP) assemblies, which then cocrystallized with fullerene C60. Those were pyrazine (1); 4,4‘-bipyridyl (2, 8, 9 (with CoTPP)); tetra(4-pyridyl)porphyrin (3); tetrahydrofuran (4); N,N,N‘,N‘-tetramethyldiaminomethane (5); N,N,N‘,N‘-tetramethyldiaminoethane (6); N,N,N‘,N‘-tetramethyldiaminobutene (7); and 1,4-bi-(4,4‘-pyridyl)ethylene (10). Molecular structures of new ZnTPP oligomers were described. ZnTPP units, concaved as a result of ligand coordination, effectively cocrystallized with nearly spherical fullerene molecules to produce a variety of packing motifs of fullerenes, namely, three-dimensional (3D) packing in 4, one-dimensional (1D) zigzag chains in 6, a pair arrangement in 1 and 3, and isolated packing in 2. The Zn···N(L) bonds were either arranged nearly parallel to the planes of the ligand or bent up to 33° relative to this plane. The characteristic Zn···N(L) bond lengths were 2.13−2.21 Å, whereas the Zn···C(C60) distances were essentially longer (3.10−3.29 Å). Coordination with ligands and C60 noticeably shifted the Soret band of ZnTPP to the red side (up to 12 nm) and two Q-bands (up to 26 nm). According to visible-NIR and IR spectra, the complexes had a neutral ground state with charge-transfer bands at 760−820 nm depending on a ZnTPP·L assembly.