Substituent effects on the isomerization of hydrazone switches driven by the intramolecular hydrogen bond

The effect of resonance-assisted hydrogen bond on the second-order nonlinear optical properties of pyridine hydrazone photoswitches: a quantum chemistry investigation

“…The observed variations in Z isomers are a result of the presence of intramolecular N1–H⋯N6 hydrogen bonding, leading to the formation of a quasi-ring structure N1–N2–C3–C4–N6⋯H (the distance N1–N6 and H⋯N6 is ∼2.691 and 1.922 Å, respectively). According to the literature and our calculations, this quasi-ring structure is almost planar 58–65 (see Table S2, ESI†) and distinguished by short N1–N6 distances and longer H–N1 bonds ( r HN 1 , Z ≈ 1.018 Å and r HN 1 , E ≈ 1.012 Å). Furthermore, analysis using QTAIM indicates a delocalization of electrons within the quasi-cycle closed (RCP).…”

Theoretical, Solid‐State, and Solution Quantification of the Hydrogen Bond‐Enhanced Halogen Bond

“…In contrast, the consideration of heavier halogens (that halogen bond: X=Cl, Br, I) has lagged. The few studies of heavy organohalogens as hydrogen bond acceptors have largely been theoretical, [9–11] with only a handful of experimental [12–18] and database [19, 20] studies reported. The importance of addressing this deficiency is underscored by the recent proliferation of halogen bonding materials, the ubiquity of the hydrogen bond, and a recent appreciation that hydrogen bonding can significantly influence halogen bonding (vide infra).…”