Diverse Self-Assembled\nMolecular Architectures Promoted\nby C–H···O and C–H···Cl\nHydrogen Bonds in a Triad of α‑Diketone, α‑Ketoimine,\nand an Imidorhenium Complex: A Unified Analysis Based on XRD, NEDA,\nSAPT, QTAIM, and IBSI Studies

X-ray structural elucidation, supramolecular self-assembly,\nand\nenergetics of existential noncovalent interactions for a triad comprising\nα-diketone, α-ketoimine, and an imidorhenium complex are\nhighlighted in this report. Molecular packing reveals a self-assembled\n2D network stabilized by the C–H···O H-bonds\nfor the α-diketone (benzil), and the first structural report\nof Brown and Sadanaga stressing on the prevalence of <i>only\nthe van der Waals forces</i> seems to be an oversimplified conjecture.\nIn the α-ketoimine, the imine nitrogen atom undergoes intramolecular\nN···H interaction to render itself inert toward intermolecular\nC–H···N interaction and exhibits two types of\nC–H···O H-bonds in consequence to generate a\nself-assembled 2D molecular architecture. The imidorhenium complex\nfeatures a self-aggregated 3D packing engendered by the interplay\nof C–H···Cl H-bonds along with the ancillary\nC–H···π, C···C, and C···Cl\ncontacts. To the best of our knowledge, in rhenium chemistry, this\nimidorhenium complex unravels the first example of self-associated\n3D molecular packing constructed by the directional hydrogen bonds\nof C–H···Cl type. The presence of characteristic\nsupramolecular synthons, viz., R<sub>2</sub><sup>2</sup>(12), R<sub>2</sub><sup>2</sup>(16), and R<sub>2</sub><sup>2</sup>(14), in the\nα-diketone, α-ketoimine, and imidorhenium complex, respectively,\nhas prompted us to delve into the energetics of noncovalent interactions.\nSymmetry-adapted perturbation theory analysis has authenticated a\nstability order: R<sub>2</sub><sup>2</sup>(14) > R<sub>2</sub><sup>2</sup>(12) > R<sub>2</sub><sup>2</sup>(16) based on the interaction\nenergy values of −25.97, −9.93, and −4.98 kcal/mol,\nrespectively. The respective average contributions of the long-range\ndispersion, electrostatic, and induction forces are 58.5, 32.8, and\n8.7%, respectively, for the intermolecular C–H···O\ninteractions. The C–H···Cl interactions experience\ncomparable contribution from the dispersion force (57.9% on average),\nalthough the electrostatic and induction forces contribute much less,\n28.0 and 14.1%, respectively, on average. The natural energy decomposition\nanalysis has further attested that the short-range, interfragment\ncharge transfer occurring via the lp(O/Cl) → σ*(C–H)\nroutes contributes 17–25% of the total attractive force for\nthe C–H···O and C–H···Cl\ninteractions. Quantum theory of atoms in molecules analysis unfolds\na first-order exponential decay relation (<i>y</i> = 8.1043<i>e</i><sup>–<i>x</i>/0.4095</sup>) between the\nelectron density at the bond critical point and the distance of noncovalent\ninteractions. The distances of noncovalent interactions in the lattices\nare internally governed by the individual packing patterns rather\nthan the chemical nature of the H-bond donors and acceptors. Intrinsic\nbond strength index analysis shows promise to correlate the electron\ndensity at BCP with the SAPT-derived interaction energy for the noncovalent\ninteractions. Two factors: (i) nearly half the HOMO–LUMO energy\ndifference for the imidorhenium complex (∼30 kcal/mol) compared\nto the organics, and (ii) ∼60% localization of HOMO over the <i>mer</i>-ReCl<sub>3</sub> moiety clearly indicate an enhanced\npolarizability of the complex facilitating the growth of weak C–H···Cl\nH-bonds.