Abstract
In this manuscript, we use the primary source of geometrical information, i.e., Cambridge Structural Database (CSD), combined with density functional theory (DFT) calculations (PBE0-D3/def2-TZVP level of theory) to demonstrate the relevance of π-hole interactions in para-nitro substituted pyridine-1-oxides. More importantly, we show that the molecular electrostatic potential (MEP) value above and below the π–hole of the nitro group is largely influenced by the participation of the N-oxide group in several interactions like hydrogen-bonding (HB) halogen-bonding (XB), triel bonding (TrB), and finally, coordination-bonding (CB) (N+–O− coordinated to a transition metal). The CSD search discloses that p-nitro-pyridine-1-oxide derivatives have a strong propensity to participate in π-hole interactions via the nitro group and, concurrently, N-oxide group participates in a series of interactions as electron donor. Remarkably, the DFT calculations show from strong to moderate cooperativity effects between π–hole and HB/XB/TrB/CB interactions (σ-bonding). The synergistic effects between π-hole and σ-hole bonding interactions are studied in terms of cooperativity energies, using MEP surface analysis and the Bader’s quantum theory of atoms in molecules (QTAIM).
Highlights
Chemists working in supramolecular chemistry, crystal engineering, and materials science [1–3] frequently put their faith in traditional hydrogen bonding (HB) [4–6], strong donor–acceptor π-stacking interactions and, to a lesser extent, halogen bonding (XB) interactions [7–14]
We show that the molecular electrostatic potential (MEP) value above and below the π–hole of the nitro group is largely influenced by the participation of the N-oxide group in several interactions like hydrogen-bonding (HB) halogen-bonding (XB), triel bonding (TrB), and coordination-bonding (CB) (N+–O− coordinated to a transition metal)
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Summary
Chemists working in supramolecular chemistry, crystal engineering, and materials science [1–3] frequently put their faith in traditional hydrogen bonding (HB) [4–6], strong donor–acceptor π-stacking interactions and, to a lesser extent, halogen bonding (XB) interactions [7–14]. Striking and distinctive features of σ–hole interactions involving Groups 14-18 of elements with respect to HBs are the greater hydrophobicity and directionality. These features have been recently used to design catalysts that function in apolar media. Apart from the emerging σ-hole interactions, noncovalent interactions involving π-holes are gaining attention. They have been studied in trivalent boron and aluminium compounds, carbonyls, and in nitro-derivatives and related compounds [48–54]. IInn ffaacctt,, tthhee aabbiilliittyy ooff nnoonnccoovvaalleenntt ffoorrcceess ttoo ccoonnttrrooll aanndd ttuunnee hhiigghhlylyspspeceicfiificcbibnidnidnigngis iosftoefntednuedutoeatnoinantriicnattreiccaotme bcionmatbioinnaotifonnonocfonvoanlecnotvfaolrecnets faocrtcinesg accotoinpgercaotiovpeelyra[t6i2v]e.lTyh[e62u]n.
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