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Aromaticity Analysis of Lithium Cation/ π Complexes of Aromatic Systems
Author(s) -
Güell Mireia,
Poater Jordi,
Luis Josep M.,
Mó Otilia,
Yáñez Manuel,
Solà Miquel
Publication year - 2005
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200500216
Subject(s) - aromaticity , ring (chemistry) , chemistry , delocalized electron , lithium (medication) , ring size , computational chemistry , molecule , organic chemistry , medicine , endocrinology
The changes in the local aromaticity of aromatic rings on complexation with lithium cation are discussed for a series of polycyclic aromatic hydrocarbons by using, as probes of aromaticity, the para ‐delocalization index (PDI), the aromatic fluctuation index (FLU), the harmonic oscillator model of aromaticity index (HOMA), and the nucleus‐independent chemical shift (NICS). In most cases, changes in the electronically based PDI and FLU indices are almost irrelevant. For this reason, the analysis is carried out mainly with the more sensitive HOMA and NICS descriptors. These indices indicate that changes in the local aromatic character of the different rings are small. In general, Li + interacts more favorably with the ring having the largest π charge, but there is no correlation between these magnitudes. The ring directly interacting with the lithium cation suffers a slight but significant reduction of aromaticity, while the reduction of the local aromaticity of the adjacent rings is minor. For those rings located further away from the ring directly connected to Li + , we found generally a small increase in aromaticity. Although there is no clear correlation between aromaticity and Li + binding enthalpies, there is a rough correlation between the latter and the change in the aromaticity of the ring directly interacting with the metal cation.