Neutron diffraction at 15 K and ab initio molecular-orbital studies of the structure of N,N'-diformohydrazide

Ruble, J. R.; McMullan, R. K.; Defrees, D. J.; Pople, J. A.

doi:10.1107/s0567740882006244

Cited by 17 publications

(17 citation statements)

References 9 publications

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“…19 For example, low-temperature neutron diffraction measurements of a single crystal of urea, 27 N,N′-diformohydrazide, 28 and acetamide 29 indicate the CO bond to be significantly longer and the CN bond to be shorter than the corresponding values calculated by ab initio methods. 19 For example, low-temperature neutron diffraction measurements of a single crystal of urea, 27 N,N′-diformohydrazide, 28 and acetamide 29 indicate the CO bond to be significantly longer and the CN bond to be shorter than the corresponding values calculated by ab initio methods.…”

Section: Resultsmentioning

confidence: 99%

Amidine N−C(N)−N Skeleton: Its Structure in Isolated and Hydrogen-Bonded Guanidines fromab InitioCalculations

et al. 1996

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Geometries of guanidine and eight of its N-imino derivatives (CH 3 , SiH 3 , OH, CN, F, Cl, CHO, and NO 2 ) were calculated using ab initio molecular orbital techniques. MP2, MP4, and CISD geometries indicate that the guanidine molecule is pyramidal at amino groups and π-conjugation through the amidine skeleton is modest. MP2 structures of the eight N-imino guanidines reveal that substituting the hydrogen atom of the imino nitrogen by a functional group leads to a concerted variation of the CN bond distances. Topological electron density analyses indicate that the structural changes calculated upon N-imino substitution are largely due to changes of conjugation onto the amidine π-skeleton. Intermolecular hydrogen bonding involving the imino and amino groups is also found to affect the amidine geometry. Special attention has been paid in the work of 2-cyanoguanidine. The centrosymmetric dimer and a more extended hydrogen-bonded complex have been proposed as simulation of the crystal environment and the respective ab initio geometries (HF/ 4-31G(d) and MP2/6-31G(d)) are discussed. The structural changes due to self-association have been rationalized supposing that the contribution of polar canonical forms increases upon hydrogen-bonding formation.

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Section: Resultsmentioning

confidence: 99%

Amidine N−C(N)−N Skeleton: Its Structure in Isolated and Hydrogen-Bonded Guanidines fromab InitioCalculations

et al. 1996

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“…Refinement (C) gives less anisotropic ADPs than (A). The bond lengths of N-H(N) and C-H(C) in Table 3 increase from 0.9140 (7) and 0.9920 (7) A ˚in refinement (A) to 1.033 (3) and 1.032 (2) A ˚for (C), respectively, though they are still shorter than the values of 1.0385 (7) and 1.0997 (7) A ˚, respectively, determined by neutron diffraction at 15 K (Jeffrey et al, 1982).…”

Section: Discussionmentioning

confidence: 71%

“…The MOs calculated here are called RHF-MOs (where RHF stands for restricted Hartree Fock) and those obtained by XMO analysis in Section 4.2.4 are called XMO-MOs. Bond lengths and angles for the molecule are listed in column (E) and those determined by neutron diffraction (Jeffrey et al, 1982) are listed for reference in column (D) of Table 3. Since the R factor for the theoretical molecule transferred to the crystal lattice was high, 0.05788, CrPs including anisotropic ADPs for H atoms, as well as the type-II extinction parameters, were refined fixing the RHF-MOs.…”

Section: Refinement (B) Of Crps Fixing the Mos Calculated Bymentioning

confidence: 99%

“…Assuming C 2h symmetry for the DFH molecule, starting MOs for the present XMO analysis were calculated using HONDO-8. The atom coordinates determined in Section 4.1 were modified a little to fit to C 2h symmetry, and the N-H(N) and C-H(C) bonds were extended to 0.998 and 1.079 A ˚, respectively, which were calculated by ab initio MO theory with the 3-21G basis set (Jeffrey et al, 1982). The CrPs, including anisotropic ADPs for H atoms and an isotropic type-II extinction parameter, were refined fixing the calculated MOs and then an anisotropic type-II extinction was applied.…”

Section: Refinement (B) Of Crps Fixing the Mos Calculated Bymentioning

confidence: 99%

“…The structure of DFH was also studied by neutron diffraction (ND) at 15 K and the C-H and N-H bond lengths were determined to be 1.0997 (7) and 1.0985 (7) A ˚, respectively. The results were also compared with the 3-21G ab initio MO calculation (Jeffrey et al, 1982). The ED of DFH at 296 K was also measured by Tanaka (1978).…”

Section: Introductionmentioning

confidence: 99%

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X-ray molecular orbital analysis. II. Application to diformohydrazide, (NHCHO)₂

Tanaka

Wasada-Tsutsui

2021

Acta Cryst Sect A

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The molecular orbitals (MOs) of diformohydrazide have been determined from the electron density measured by X-ray diffraction. The experimental and refinement procedures are explained in detail and the validity of the obtained MOs is assessed from the crystallographic point of view. The X-ray structure factors were measured at 100 K by a four-circle diffractometer avoiding multiple diffraction, the effect of which on the structure factors is comparable to two-centre structure factors. There remained no significant peaks on the residual density map and the R factors reduced significantly. Among the 788 MO coefficients, 731 converged, of which 694 were statistically significant. The C—H and N—H bond distances are 1.032 (2) and 1.033 (3) Å, respectively. The electron densities of theoretical and experimental MOs and the differences between them are illustrated. The overall features of the electron density obtained by X-ray molecular orbital (XMO) analysis are in good agreement with the canonical orbitals calculated by the restricted Hartree Fock (RHF) method. The bonding-electron distribution around the middle of each bond is well represented and the relative phase relationships of the π orbitals are reflected clearly in the electron densities on the plane perpendicular to the molecular plane. However, differences are noticeable around the O atom on the molecular plane. The orbital energies obtained by XMO analysis are about 0.3 a.u. higher than the corresponding canonical orbitals, except for MO10 to MO14 which are about 0.7 a.u. higher. These exceptions are attributed to the N—H...O′′ intermolecular hydrogen bond, which is neglected in the MO models of the present study. The hydrogen bond is supported by significant electron densities at the saddle points between the H(N) and O′′ atoms in MO7, 8, 14 and 17, and by that of O′′-p extended over H(N) in MO21 and 22, while no peaks were found in MO10, 11, 13 and 15. The electron density of each MO clearly exhibits its role in the molecule. Consequently, the MOs obtained by XMO analysis give a fundamental quantum mechanical insight into the real properties of molecules.

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Crystal and Molecular Structure of the Smectogen 1‐[4‐n‐heptylbenzoyl]‐2‐[cyanoacetyl]‐hydrazine

Pfeiffer¹,

Kretschmer²,

Hoffmann³

1986

Cryst. Res. Technol.

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Neutron diffraction at 15 K and ab initio molecular-orbital studies of the structure of N,N'-diformohydrazide

Abstract: The crystal structure of N,N'-diformohydrazide ( 1,2-hydr azinedic arboxaldehyde), C 2H4N 202, has been refined using single-crystal neutron diffraction

Cited by 17 publications

References 9 publications

Amidine N−C(N)−N Skeleton: Its Structure in Isolated and Hydrogen-Bonded Guanidines fromab InitioCalculations

Amidine N−C(N)−N Skeleton: Its Structure in Isolated and Hydrogen-Bonded Guanidines fromab InitioCalculations

X-ray molecular orbital analysis. II. Application to diformohydrazide, (NHCHO)₂

Crystal and Molecular Structure of the Smectogen 1‐[4‐n‐heptylbenzoyl]‐2‐[cyanoacetyl]‐hydrazine

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Neutron diffraction at 15 K and ab initio molecular-orbital studies of the structure of N,N'-diformohydrazide

Abstract: The crystal structure of N,N'-diformohydrazide ( 1,2-hydr azinedic arboxaldehyde), C 2H4N 202, has been refined using single-crystal neutron diffraction

Cited by 17 publications

References 9 publications

Amidine N−C(N)−N Skeleton: Its Structure in Isolated and Hydrogen-Bonded Guanidines fromab InitioCalculations

Amidine N−C(N)−N Skeleton: Its Structure in Isolated and Hydrogen-Bonded Guanidines fromab InitioCalculations

X-ray molecular orbital analysis. II. Application to diformohydrazide, (NHCHO)2

Crystal and Molecular Structure of the Smectogen 1‐[4‐n‐heptylbenzoyl]‐2‐[cyanoacetyl]‐hydrazine

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X-ray molecular orbital analysis. II. Application to diformohydrazide, (NHCHO)₂