Energy and Planarity in Boron‐Nitrogen Fulvene Isomers: A Quantum‐Chemical and QSPR Study

Quantum‐chemical computations at the M06‐2X/def2TZVP level of theory are used to determine the minimum energy geometries and relative energies of all of the boron‐nitrogen fulvene isomers that correspond to sequential isoelectronic replacements in fulvene of the type {CC ↔ BN}. Compact Quantitative Structure–Property Relationships (QSPR) regression and classification models for the energetics and planarity/nonplanarity of these isomers are developed using structural molecular descriptors of the fragment type that involve atom types and the connectivity pattern. It is shown that the energies of the boron‐nitrogen fulvene isomers can be reproduced/predicted with just four structural descriptors, namely the numbers of C, CCH, NN, and BBH fragments, with a root mean square error in the energy of 0.019 au and with a coefficient of determination of 0.9999 for the training set. In addition, the classification of the molecules into planar or nonplanar structures achieves an average sensitivity of 0.9583 for calibration when using only three descriptors: the numbers of BNNB, BBCNH, and NN fragments.