Planarity does not always mean higher aromaticity – Intriguing metalloaromaticity of three Al13+ isomers

Publication date: Available online 23 January 2020Source: Journal of Molecular Graphics and ModellingAuthor(s): Surajit Guin, Sourav Ranjan Ghosh, Atish Dipankar JanaAbstractA pair of Al13+ clusters, one perfectly planar (CI) and another quasi-planar structure (CII) have been reported recently by our group [Guin et al. Journal of Molecular Modeling, 2018, 24, 344]. Both these clusters are rare examples of metal-aromatic systems having unique aromatic character. In these clusters localized strong anti-aromatic deltas are embedded within a strong aromatic sea. The quasi-planar CII structure is a true minimum structure with zero imaginary frequency, but the planar CI structure has been found to have three imaginary frequencies. Further search for a possible transition structure (CT) with single imaginary frequency was successful which shows that CT structure is also quasi-planar but the tail region of this cluster is puckered downward as compared to that of the CII cluster for which tail region is puckered upward. A comparative electronic structural analysis of these three clusters have been carried out which has provided insight into the way the transformation among the three states take place. Harmonic frequency analysis of these clusters reveals that transition from CT to CII occurs through the planar cluster CI that appears to have an intermediate geometry between the downwardly puckered CT and the upwardly puckered CII. A comparative NICS, ELF, AIM and LOL analysis of all t...
Source: Journal of Molecular Graphics and Modelling - Category: Molecular Biology Source Type: research