Abstract
A new diaziridine derivative with two bicyclic diaziridine-containing moieties in one molecule, 6,6′-dimethyl-1,1′,5,5′-tetraaza-6,6′-bi(bicyclo[3.1.0]hexane) (BiDiMDAH), has been synthesized for the first time. Its molecular structure has been investigated in the gas phase by means of quantum-chemical (QC) calculations, in CDCl3 solution by 1D and 2D NMR spectroscopy and in the solid state by the X-ray diffraction (XRD) technique. It was found by QC calculations that BiDiMDAH molecule in a free state presents a single conformer of C2 symmetry with trans orientation of the methyl groups about two carbons connecting diaziridine cycles. The 5-memebered rings in BiDiMDAH molecule has been found to be essentially planar. In order to explain conformational preferences of BiDiMDAH, natural bond orbitals (NBO) and atoms in molecules (AIM) analyses have been performed. According to the XRD data, BiDiMDAH crystallizes in space group P21/c with molecular structure resembling the structure obtained by the means of QC calculations for the lowest energy form. However, the relative arrangement of the methyl groups of the solid BiDiMDAH molecule is similar to that of the one of the transition states. The data of NMR spectroscopy has revealed that only one conformer is present in CDCl3 solution in agreement with the data of QC and XRD studies. The gaseous standard enthalpy of formation of BiDiMDAH has been estimated to be 106.1±1.2 kcal/mol by means of G4 theory.
Highlights
The study of conformational properties and molecular structure of diaziridines (1,2-diazacyclopropanes) comes in a field of our scientific interests for many years [1,2,3,4,5,6,7,8,9,10,11,12,13]
Earlier we studied the molecular structures and peculiarity of conformational behavior of bicyclic diaziridine derivatives − 1,5-diazabicyclo[3.1.0]hexane 1 (DABH) by the gas electron diffraction (GED) method [7] and 6.6′-bis(1,5-diazabicyclo[3.1.0]hexane) 2 – by the X-ray diffraction (XRD) [1] and the gas electron diffraction (GED) [4] methods
We investigated the molecular structure of 6,6-dimethyl-1,5diazabicyclo[3.1.0.]hexane 3 by the GED and the XRD methods [3]
Summary
The study of conformational properties and molecular structure of diaziridines (1,2-diazacyclopropanes) comes in a field of our scientific interests for many years [1,2,3,4,5,6,7,8,9,10,11,12,13]. Strained diaziridine ring is inclined to ring-expansion reactions resulting in various five-to-eight-membered monoand bicyclic heterocyclic structures [24,25,26,27,28,29,30] These heterocycles possess high enthalpies of formation and though they contain hydrazine fragment are of low toxic compounds. We have studied the molecular structure of tetramezine [1,2-bis-(3,3-dimethyldiaziridin-1-yl)ethane], containing two diaziridine cycles in one molecule, by the GED method together with vibrational spectroscopy and quantum chemical calculations [33]. The results of theoretical and experimental investigations of molecular structure of 6,6'-dimethyl-1,1',5,5'-tetraaza-6,6'-bi(bicyclo[3.1.0]hexane) (BiDiMDAH) (4), containing two DABH cycles in one molecule, by the means of QC calculations, NMR spectroscopy and XRD analysis are presented
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