Interactions of metalloporphyrins as donors with the electron acceptors C60, tetracyanoquinomethane (TCNQ) and trinitrofluorenylidenemalonitrile

Abstract

Crystals of C₆₀·Pt^II(OEP)·2(C₆H₆), TCNQ·Cu^II(OEP), TCNQ·H₂(OEP), TCNQ·2Cu^II(OEP), TCNQ·2Zn^II(OEP) and TNFM·Co^II(OEP) [OEP is the dianion of octaethylporphyrin, TCNQ is 7,7,8,8-tetracyanoquinodimethane, TNFM is (2,4,7-trinitrofluorenylidene)malonitrile] have been obtained by diffusion of a solution of the porphyrin as donor into a solution of the respective acceptor molecule. The structure of C₆₀·Pt^II(OEP)·2(C₆H₆) consists of an ordered C₆₀ cage nestled against the platinum porphyrin which makes close face-to-face contact with another Pt^II(OEP) molecule. In contrast, there are no close face-to-face contacts between porphyrins in the crystal structures of TCNQ·Cu^II(OEP), TCNQ·H₂(OEP), and TNFM·Co^II(OEP). These compounds consist of classical donor–acceptor stacks of interleaved porphyrin and TCNQ or TNFM molecules with separations of ca. 3.3 Å between adjacent molecules. However with TCNQ·2Cu^II(OEP) and TCNQ·2Zn^II(OEP) the structures involve TCNQ (A) and M^II(OEP) (D) molecules that crystallize in stacks with a DDA(DDA)_nDDA arrangement. Within these stacks there are pairwise contacts between M^II(OEP) molecules and these pairs are compared to those found in C₆₀·Pt^II(OEP)·2(C₆H₆) and related fullerene-containing crystals.