Singlet–Triplet Transitions in the Dianionic Complex of Fullerene C 60 with Iron Carbonyl: (TBA + ) 2 {[Fe 2 (CO) 6 ]-η 2 ,η 2 -C 60 } 2–

Inorganic Chemistry. 2026. Vol. 65. No. 16. P. 9107–9115.

Sobov P. A., Yakushev I. A., Shestakov A., Faraonov M., Otsuka A., Kitagawa H., Konarev D.

Interaction of fullerene C60 with Cs2Fe­(CO)4 in the presence of two equivalents of tetrabutylammonium iodide (TBAI) yields the first dianionic coordination complex of fullerene: (TBA+)2{[Fe2(CO)6]-η2,η2-C60}2– (1). According to magnetic data and DFT calculations, complex 1 has a diamagnetic ground (S = 0) and a triplet excited state (S = 1) populated above 80 K. As a result, a new broad EPR signal appears, whose integral intensity grows with temperature; the estimated singlet–triplet energy gap is 508 ± 8 K. The broad signal attributed to the triplet has g = 2.0046 with a line width of 5.6 mT at 140 K, and this signal is shifted to smaller g-factors (2.0000) and narrows as the temperature increases. Calculations also show that the singlet–triplet gap is defined by the positions of the cations close to the Fe2(CO)6 fragment or the fullerene cage. According to DFT calculations, the negative electron density is mainly localized on the fullerene cage (−1.051) in the singlet state, and this charge even increases to −1.204 in the triplet state of the complex. Spin density localized on Fe2(CO)6 is concentrated on only one of the two iron atoms.

Keywords: фуллерены, Fullerene