Novel quintet and triplet (nitrenoethynyl)halomethylenes at theoretical levels

Abstract

Coupling of a local triplet carbene with a local triplet nitrene through an acetylene linkage gives a new brand of high spin quintet minima (XÀ C ÁÁ ÀC CÀ N ÁÁ ÁÁ ,where X = H, F, Cl, Br), which are rather experimentally unreachable. Placing the same linkage between the local open-shell singlet carbene (r 1 p 1 ) and the local triplet nitrene (p 1 p 1 ) gives triplet minima which are 54-56 kcal/mol more stable than their corresponding quintets. The carbenic angles in both quintets and triplets follow electropositivity of X (H [ Br [ Cl [ F), with every divalent angle in quintet being smaller than the corresponding one in the triplet. Finally no reactive intermediate is observed through connecting singlet states of carbene and nitrene subunits which gives a neutral linear molecule with X-C:C-C:N formula, and show about 70 kcal/mol more stability than the corresponding triplet states. Our results are compared at B3LYP, HF, MP2, MP4(SDTQ), CCSD(T), and QCISD(T) levels using 6-311??G** basis set.

A theoretical study of electronic effects in alkyne‐linked reactive intermediates: (nitrenoethynyl)methylenes, (nitrenoethynyl)silylenes, and (nitrenoethynyl)germylenes

“…Following our quest for new carbenonitrenes,[6b] in this work we compare and contrast the effect of electron‐donating and electron‐withdrawing groups on the structure, dipole moment, charge transfer, atom hybridization, stability, HOMO–LUMO band gap, and chemical reactivity of (nitrenoethynyl)‐X‐methylenes, (nitrenoethynyl)‐X‐silylenes, and (nitrenoethynyl)‐X‐germylenes X–M–C≡C–N at B3LYP, M06‐2X, HF, and MP2 levels with 6–311++G(d,p) basis set, for X = H ( 1 ), CN ( 2 ), OH ( 3 ), NH 2 ( 4 ), NO 2 ( 5 ), and CHO ( 6 ); M = C, Si, and Ge (Figures and S1, Tables ). The MP2/6–311++G(d,p)‐optimized structures were used as inputs for single‐point calculation at MP4, CCSD(T), and QCISD(T) levels with the same basis set because of the improvement in the level of confidence of predictions…”

“…This provided more trust on these computational results. Hence, B3LYP/6–311++G(d,p) was adopted for discussion, as was also done in many other computational works [6a,b,12] …”

“…In spite of the fact that the C=C double bond or C≡C triple bond seems to be a suitable linkage for coupling two reactive centers, few studies have been reported in this regard [3d,6]. Hence, following our previous studies, in this work we study (nitrenoethynyl)‐X‐methylenes, (nitrenoethynyl)‐X‐silylenes, and (nitrenoethynyl)‐X‐germylenes at the theoretical level (X–M–C≡C–N; X=H ( 1 ), CN ( 2 ), OH ( 3 ), NH 2 ( 4 ), NO 2 ( 5 ), and CHO ( 6 )); M=C, Si, and Ge) (Figures and S1).…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…As little is known about multiple bonds linking two reactive centers Kassaee et al [62] continued their related investigations using DFT on unstable and experimentally difficult to obtain the (nitrenoethynyl)halomethylenes, N-C:C-C-X (X = H, F, Cl, Br). Triplet minima are 54-56 kcal mol -1 more stable than their corresponding quintets.…”