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Inorganica Chimica Acta
Volume 533, 2022, 120789

Different types of interactions between fullerene C60 and C70 anions and metal tetraphenylporphyrins in the (PMDAE+)(MIITPP)(Fullerene-). Solvent complexes (M = Co, Mn, Zn) containing coordinating N, N, N, N, N-pentamethyldiaminoethane cations

Mikhail G. Andronova, Alexey V. Kuzminb, Alexander F. Shestakova

Institute of Problems of Chemical Physics RAS, Chernogolovka, Moscow region 142432, Russia.

Abstract

Series of anionic salts of fullerenes C60 and C70 with different metal tetraphenylporphyrins, MIITPP, where M = Co, Mn and Zn, and NNNN‘, N‘-pentamethyldiaminoethane cations (PMDAE+) has been obtained in a crystalline form. Composition of the complexes is (PMDAE+) (MIITPP)(C60−) XC6H4Cl2 (M = Co, X  = 1.25 (1), M = Mn, X  = 0.75 (2) and M = Zn, X  = 0.75 (3)) and {(PMDAE+)⋅ZnIITPP}2⋅(C70−)2 4C6H4Cl2 (4). Both fullerene anion and nitrogen-containing PMDAE+ cation can coordinate to metal porphyrin competing with each other. Weak Co-C(C60−) coordination bond of 2.426(7) Å length (120 K) is formed in 1 whereas PMDAE+ cation only weakly coordinates to CoIITPP. Dissociation of Co-C(C60−) bond observed at 90–310 K is accompanied by a transition of 1 from singlet to triplet state with an energy gap of 574 ± 3 K. According to the calculations negative charge on C60− is only −0.548 due to electron transfer to the macrocyclic ligand through the cobalt atom. Charge transfer bands are observed in {CoIITPP(C60)}− at 700 and 1240 nm. On the contrary, PMDAE+ cations coordinate to MnIITPP and ZnIITPP in 2 and 3, respectively, with short M−N(PMDAE+) bonds of 2.27–2.33 Å length. In these cases fullerenes are preserved in the non-coordinated radical anion state. Fullerenes are arranged in closely packed π-stacking {C60•−}2 dimers with short interfullerene center-to-center distances of 9.92–9.95 Å. Nevertheless, the C60•− radical anions do not form intercage CC bonds down to 1.9 K. Strong antiferromagnetic coupling of spins is observed in the {C60•−}2 dimers of 3 with exchange interaction of J/kB = -21 K. Both {(PMDAE+)⋅MnIITPP} and C60•− species are paramagnetic in 2 having S = 5/2 and S = 1/2 spin states, respectively. These spins are coupled antiferromagnetically with Weiss temperature of −16 K. It is obvious that magnetic coupling occurs not only in the {C60•−}2 dimers but MnIITPP is also involved in this coupling. The C70•− radical anions are dimerized in 4 forming diamagnetic singly-bonded (C70−)2 dimers which manifest intense NIR absorption. As a result, complex 4 is EPR silent.

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