Eilatin: Semiempirical MO Calculations of Molecular Structures and Electronic Spectra of the Unprotonated and N-Protonated Molecules

1998 ◽  
pp. 542-543
Author(s):  
Tsuguo Sato ◽  
Masahiro Kataoka
Keyword(s):  
Electronic Spectra ◽  
Molecular Structures ◽  
Mo Calculations ◽  
Semiempirical Mo Calculations ◽  
Protonated Molecules

scholarly journals Multi-scale modeling of electronic spectra of three aromatic amino acids: importance of conformational averaging and explicit solute–solvent interactions

2014 ◽  
Vol 16 (38) ◽  
pp. 20639-20649 ◽  
Author(s):  
Petr Štěpánek ◽  
Petr Bouř
Keyword(s):  
Amino Acids ◽  
Quantum Mechanics ◽  
Molecular Mechanics ◽  
Electronic Spectra ◽  
Aromatic Amino Acids ◽  
Molecular Structures ◽  
Solvent Interactions ◽  
Multi Scale ◽  
Scale Modeling ◽  
Multi Scale Modeling

Electronic spectra provide a wealth of information on molecular structures. We demonstrate a very satisfactory agreement between experimental and modeled spectra, as obtained by combined molecular mechanics/quantum mechanics computations for three aromatic amino acids.

Structural and spectroscopic studies of transition metal nitrite complexes. V. Crystal structures and spectra of trans-Tetrakis(pyridine)dinitritonickel(II)-pyridine (1/2), trans-Tetrakis(4-methylpyridine)dinitritonickel(II) and trans-Tetrakis(pyrazole)-dinitritonickel(II)

1981 ◽  
Vol 34 (10) ◽  
pp. 2095 ◽  
Author(s):  
AJ Finney ◽  
MA Hitchman ◽  
CL Raston ◽  
GL Rowbottom ◽  
BW Skelton ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Transition Metal ◽  
Crystal Structures ◽  
Electronic Spectra ◽  
Spectroscopic Studies ◽  
Molecular Structures ◽  
Aromatic Rings ◽  
Paddle Wheel ◽  
Crystal And Molecular Structures ◽  
Infrared Frequencies

The crystal and molecular structures of the compounds [Ni(py)4(ONO)2],2py, [Ni(γmpy),(ONO)2] and [Ni(prz)4(ONO)2] are reported.�All three are trans nitrito complexes, the pyridine (py) compound containing two pyridine molecules of solvation. The aromatic rings in the first two complexes adopt 'paddle wheel' conformations with pitch angles varying between 40 and 70�. The nitrite ions are positioned so as to minimize repulsive interactions with the amines, and it seems likely that these groups bond through oxygen rather than nitrogen because this allows a lesser degree of interligand steric interference. The amine rings in [Ni(prz)4(ONO)2] are orthogonal to the plane containing the nickel and coordinated pyrazole nitrogen atoms; the nitrito groups are disordered between two inequivalent positions, each of which involves hydrogen bonding with the pyrazole NH groups. The nitrite infrared frequencies are similar to those observed for other nickel(II) nitrito complexes except that the antisymmetric NO stretching mode of one of the groups in the pyrazole complex is much lower in energy than expected, being in the range normally associated with a nitrogen-bonded or chelated nitrite group. It is suggested that this deviation may be caused by the hydrogen bonding in the complex. The electronic spectra of the compounds yield 10Dq values of 9100 and 8500 cm-1 for the nitrite ligands in [Ni(py)4(ONO)2] and Ni(prz)4(ONO)2], respectively, placing the nitrito group towards the weaker end of the spectro-chemical series.

Experimental and computational structural study of two hindered aminoanthraquinones in crystals and solutions

2000 ◽  
Vol 215 (9) ◽  
Author(s):  
A.V. Yatsenko ◽  
K.A. Paseshnichenko ◽  
S.I. Popov
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
Electronic Spectra ◽  
Molecular Structures ◽  
Amino Group ◽  
Single Crystal Diffraction ◽  
Molecular Conformations ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Visible Spectra

The crystal and molecular structures of 2-methyl-1-methylamino-anthraquinone (I) and 1-methylphenylamino-anthraquinone (II) were studied by the X-ray single-crystal diffraction and the visible spectra of crystalline specimens and their solutions were recorded. The molecule I is closely planar, whereas in the molecule II the amino group is 58° rotated out of the plane of the anthraquinone skeleton. In both structures the molecules pack in stacks. The comparison of experimental and calculated (on the DFT and AM1 levels) molecular structures, together with the comparison of experimental and INDO/S-calculated electronic spectra, give the evidence that molecular conformations (especially for II) change upon transfer from the solid state to solutions, and the π-delocalisation throughout the whole molecule enhances in the solid state.

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