Dative or coordinative carbon−boron bond in boron trapped N-heterocyclic carbenes (NHCs)? An answer given on the magnetic criterion

Bonding, Aromaticity and Isomerization of Furfuraldehyde through Off-Nucleus Isotropic Magnetic Shielding

Off-nucleus isotropic magnetic shielding (σiso (r)) and multi-points nucleus independent chemical shift (NICS(0-2 Å)) index were utilized to find the impacts of the isomerization of gas-phase furfuraldehyde (FD) on bonding and aromaticity of FD. Multidimensional (1D to 3D) grids of ghost atoms (bqs) were used as local magnetic probes to evaluate σiso (r) through gauge-including atomic orbitals (GIAO) at density functional theory (DFT) and B3LYP functional/6-311+G(d,p) basis set level of theory. 1D σiso (r) responses along each bond of FD were examined. Also, a σiso (r) 2D-scan was performed to obtain σiso (r) behavior at vertical heights of 0-1 Å above the FD plane in its cis, transition state (TS) and trans forms. New techniques for evaluating 2D σiso (r) cross-sections are also included. Our findings showed that bonds in cyclic and acyclic parts of FD are dissimilar. Unlike the C-O bond of furanyl, the C=O bond of the formyl group is magnetically different. C-C and C-H bonds in furanyl are found similar to those in aromatic rings. A unique σiso (r) trend was observed for the C2 -C6 bond during FD isomerization. Based on NICS(0-2 Å) values, the degree of aromaticity follows the order of cis FD Collapse

Key Words

• aromaticity
• chemical bonding
• furfuraldehyde
• nucleus-independent chemical shift NICS
• off-nucleus isotropic shielding

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Affiliation(s)

Muntadar A. H. Al‐Yassiri Department of Chemistry – College of ScienceUniversity of BaghdadAl-JadiryaBaghdadIraq

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