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Towards Rational Syntheses of the Elusive Metallocarbohedrenes: Density Functional Prescriptions for Electronic and Geometric Structures
Author(s) -
Dance Ian,
Wenger Eric,
Harris Hugh
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020802)8:15<3497::aid-chem3497>3.0.co;2-w
Subject(s) - density functional theory , rational design , context (archaeology) , singlet state , paramagnetism , ground state , molecule , computational chemistry , magnetism , band gap , chemistry , electronic structure , fullerene , chemical physics , homo/lumo , materials science , nanotechnology , physics , atomic physics , organic chemistry , condensed matter physics , paleontology , optoelectronics , biology , excited state
The metallocarbohedrenes are binary molecular clusters containing metal atoms linked by acetylenediide C 2 groups. Hundreds of these molecules have been generated, detected and reacted in the gas phase since the prototype, [Ti 8 (C 2 ) 6 ], was reported in 1992, but none has yet been synthesised pure in bulk: the time gap between detection and preparation increasingly exceeds that of the fullerenes. We report here the results of density functional calculations of geometrical and electronic structure of more than 150 postulated metallocarbohedrenes, stabilised by terminal ligation, in order to recognise the more electronically favourable and less reactive targets. At least 38 metallocarbohedrenes have been identified as having a spin singlet ground state, with a relatively large (> 0.5 eV) energy gap between HOMO and LUMO, and an appropriate HOMO energy. In addition, a considerable number of electronically stable metallocarbohedrenes are predicted to have highly paramagnetic ground states, potentially useful in molecular magnetism. The geometrical principles for enclosing but unstrained coordination of metal sites by terminal ligands are outlined. Mechanisms for rational syntheses are considered in the context of reaction type and precursor selection, including issues of oxidation and reduction, and kinetic versus thermodynamic control. This leads to many diverse reactions suggested for the rational syntheses of metallocarbohedrenes. Some preliminary experimental results are presented.