Possibility of the Existence of Donor–Acceptor Interactions in Bis(azole)amines: An Electronic Structure Analysis

Abstract

Donor-stabilized divalent N(I) systems have recently gained attention in the field of organic chemistry. Existence of low-valent nitrogen(I) species with moderate nucleophilicities in several pharmacophoric functionalities is prompting extensive exploration in this field. Quantum chemical analysis on the imidazole, oxazole, and thiazole derivatives of thiazole-2-amine indicated that these species preferably exist in the iminic state. Electronic structure analysis of these systems suggested the existence of hidden divalent N(I) character in a neutral state (L → N-R) and the explicit divalent N(I) character (L → N ← L)(+) in the protonated state. The strength of L → N interaction in these systems was analyzed, and the variations in the nucleophilicity trend at the coordinating nitrogen center were rationalized by estimating the electronic (TEP (Tolman electronic parameter) and MESP minimum (V(min))) as well as steric parameters (r-repulsiveness and ΔH elimination of CO group, in L → Ni(CO)3) of the coordinating ligands L. The importance of energetically preferred ionic and tautomeric representations of thiazol-2-amine derivatives in iminic and aminic forms was also demonstrated by carrying out comparative docking analysis with the enzyme lymphocyte-specific kinase (Lck).

NL2+ Systems as New-Generation Phase-Transfer Catalysts

“…NL 2 + systems ( IV ) have been thoroughly analyzed using various quantum chemical methods for their unique electronic and structural properties. − These species (labeled as nitreones) were shown to be analogous and isoelectronic to carbones. − In NL 2 + systems, the central nitrogen atom is considered as an electron-accepting center with a formal positive charge and the ligand L is an electron-donating ligand such as N -heterocyclic carbene (NHC) (Figure ). A few related systems with L → N–R ( VI ) and L → N–N ← L ( VII ) − character were also studied.…”

“…This concept is not limited to carbon and nitrogen atoms but is also applicable to boron and other heavy congeners of groups 13, 14, and 15. Numerous compounds with the general formulas L → E ← L (where E = BH, , Al, , Ga, , C, − Si, − Ge, − N + , − ,,, and P + − and L = NHC, PPh 3 , carbocyclic carbene, CO, N 2 , etc.) and L → E–E′ ← L (where E/E′ = B, , Si, Ge, N, ,, P, and As , and L = NHC and PPh 3 ) were synthesized, isolated, and analyzed using experimental as well as theoretical methods.…”

Design, synthesis, biological evaluation and toxicity studies of N,N-disubstituted biguanides as quorum sensing inhibitors

“…As these compounds are highly basic; they readily form their salts. This property is being exploited in the preparation of oral formulations of biguanide derivatives (Setter et al, 2003) and studies on their drug action based on divalent N(I) character are in progress (Bharatam et al, 2005;Bharatam, 2011, 2009;Bhatia et al, 2013Bhatia et al, , 2012Bhatia and Bharatam, 2014).…”

Electronic structure and conformational analysis of P218: An antimalarial drug candidate

“…This observation is similar to that of cycloguanil in which similar nitrogen center was shown to carry divalent N(I) character. The comparison of the geometric and electronic features of P218 with already reported divalent N(I) compounds such as metformin and cycloguanil suggest that P218 also can be considered as a species with the (L→N←L′) ⊕ structure. The CN bond lengths are 1.32 Å and 1.34 Å (Figure B).…”

“…P218 is reported to be an HCl salt, no attempt is made to obtain it in the neutral form (to the best of our knowledge). However, the two compounds [46,[60][61][62][63][64] such as metformin [48] and cycloguanil [47] suggest that P218 also can be considered as a species with the (L!N L 0 ) structure. The CAN bond lengths are 1.32 Å and 1.34 Å ( Figure 3B).…”