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- Title
Control of Exchange Interactions in π Dimers of 6-Oxophenalenoxyl Neutral π Radicals: Spin-Density Distributions and Multicentered-Two-Electron Bonding Governed by Topological Symmetry and Substitution at the 8-Position.
- Authors
Nishida, Shinsuke; Kawai, Junya; Moriguchi, Miki; Ohba, Tomohiro; Haneda, Naoki; Fukui, Kozo; Fuyuhiro, Akira; Shiomi, Daisuke; Sato, Kazunobu; Takui, Takeji; Nakasuji, Kazuhiro; Morita, Yasushi
- Abstract
The tri- tert-butylphenalenyl (TBPLY) radical exists as a π dimer in the crystal form with perfect overlapping of the singly occupied molecular orbitals (SOMOs) causing strong antiferromagnetic exchange interactions. 2,5-Di- tert-butyl-6-oxophenalenoxyl (6OPO) is a phenalenyl-based air-stable neutral π radical with extensive spin delocalization and is a counter analogue of phenalenyl in terms of the topological symmetry of the spin density distribution. X-ray crystal structure analyses showed that 8- tert-butyl- and 8-( p-XC6H4)-6OPOs (X=I, Br) also form π dimers in the crystalline state. The π-dimeric structure of 8- tert-butyl-6OPO is seemingly similar to that of TBPLY even though its SOMO-SOMO overlap is small compared with that of TBPLY. The 8-( p-XC6H4) derivatives form slipped stacking π dimers in which the SOMO-SOMO overlaps are greater than in 8- tert-butyl-6OPO, but still smaller than in TBPLY. The solid-state electronic spectra of the 6OPO derivatives show much weaker intradimer charge-transfer bands, and SQUID measurements for 8-( p-BrC6H4)-6OPO show a weak antiferromagnetic exchange interaction in the π dimer. These results demonstrate that the control of the spin distribution patterns of the phenalenyl skeleton switches the mode of exchange interaction within the phenalenyl-based π dimer. The formation of the relevant multicenter-two-electron bonds is discussed.
- Subjects
DIMERIZATION; SPIN-density functional theory; MOLECULAR orbitals; ANTIFERROMAGNETIC materials; ELECTRON delocalization; X-ray crystallography; SOLID state chemistry
- Publication
Chemistry - A European Journal, 2013, Vol 19, Issue 36, p11904
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201301783