Electronic Communication between S=1/2 Spins in Negatively‐charged Double‐caged Fullerene C₆₀ Derivative Bonded by Two Single Bonds and Pyrrolizidine Bridge

Abstract

Radical anion salt {cryptand[2.2.2] (K + )} 2 (bispheroid) 2À ·3.5C 6 H 4 Cl 2 (1)o ft he double-caged fullerene C 60 derivative,i nw hich fullerene cages are linked by a cyclobutane bridging cycle and additionally by ap yrrolizidine moiety,w as obtained. Each fullerenec age in this derivative accepts one electron on reduction, thus forming the (bispheroid) 2À dianionsw ith two interacting S = 1/2 spins on the neighboring cages. Low-temperature magnetic measurements reveal as inglet ground state of the bispheroid dianions whereas triplet contributions prevail at increased temperature. An estimated exchange interaction betweent wo spins J/k B = À78 Ki n1 indicatess trong magnetic coupling between them,n early two times higher than that (J/k B = À44.7 K) in previously studied (C 60 À ) 2 dimers linked via ac yclobutane bridge only.T he enhancement of magnetic coupling in 1 can be explained by as horter distance between the fullerenec ages and, possibly,a na dditional channel for the magnetic exchange provided by ap yrrolizidine bridge. Quantum-chemical calculations of the lowest electronic state of the dianions by meanso fm ulti-configuration quasi-degenerate perturbation theorys upport the experimental findings.Scheme1.Molecular structure of the double-caged fullerene C 60 derivative (hereinafterbispheroid)s tudied in the present work.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Crystalline salts of anionic free-base tetrapyrazinoporphyrazines with alkyl-substituents or an extended π-electron system

“…Salts 1 and 2 are EPR silent and, therefore, diamagnetic in the whole studied temperature range. It should be noted that organic compounds with triplet (S = 1) state always show characteristic EPR signals, [45][46][47] and the absence of these signals in 1 and 2 up to 295 K clearly show that the obtained H 2 TPyzPzR 8 2À (R = Et, Me) dianions have singlet (S = 0) ground state and triplet state is not populated up to 295 K. Previously, it was also shown that H 2 TPyzPz 2À dianions are EPR silent and diamagnetic whereas EPR spectra of the H 2 TPyzPz À radical anions contain an intense narrow signal with g = 2.0025-2.0061 and the linewidth DH = 0.44-0.59 mT. 29 Moreover, the singlet ground state for the H 2 TPyzPz 2À dianions was shown by DFT calculations (the singlet-triplet energy gap was calculated to be 1130 K).…”

Paramagnetic {[Fe(CO)2]2-μ2-η2:η2-η2:η2-(C60)2}2– Dimer Bridged by Iron Atoms and C–C Bonds: Effect of Starting Iron Carbonyls on Structures and Properties of Negatively Charged Iron-Bridged Fullerene Dimers

“…The formation of C 60 •– shifts the F 1u (4) mode to 1390–1396 cm –1 . Notably, the spectrum of pristine C 60 exhibits only four IR-active modes owing to the suppression of many symmetry-forbidden modes in C 60 . As discussed earlier, both dimerization and coordination of C 60 decrease its symmetry.…”

“…Therefore, additional coordination of two Fe­(CO) 2 provides closer approach of fullerenes in the dimers . Previously, the formation of doubly bonded (C 60 ) 2 dimers was found through the coordination of two Co­(dppe) fragments as bridges or by introducing organic bridges to the C 60 cages . Additionally, in 1 , each iron atom coordinates two carbonyl groups, resulting in a coordination number of six for iron.…”

Exohedral Functionalization of Fullerene by Substituents Controlling of Molecular Organization for Spontaneous C60 Dimerization in Liquid Crystal Solutions and in a Bulk Controlled by a Potential

“…Fullerene radicals with alkyl or hydrogen substitutions can dimerize to form singly-bonded 4,4′-disubstituted adduct [ 41 ]. The electrochemistry of fullerene and fullerene dimers is of particular interest, as the redox behavior of dimeric fullerenes reflects the electronic interaction between the fullerene cages [ 42 , 43 , 44 ]. Potential values are essential for understanding and predicting the homogeneous redox properties of each particular fullerene derivative, as well as the areas of their possible application.…”