Different theoretical models used in the simulation of the structural and spectroscopic properties of Nα-Benzoyl-L-Argininate Ethyl Ester Chloride (BAEEH+·Cl−): (a) B3LYP/6-31++G(d,p) calculations of isolated BAEEH+ in vacuo, (b) B3LYP/6-31++G(d,p) calculations of a BAEEH+(H2O)5 complex in vacuo, and (c) CPMD calculations under periodic boundary conditions of a BAEEH+·Cl− crystal. The three theoretical models were established from the x-ray crystallographic data.
ORTEP diagram of BAEEH+·Cl−. The ellipsoids were drawn at the 30% probability level for clarity reasons. The alternative conformations of the ethyl groups are shown. Black and dashed lines are used for the minor and major components, respectively.
H-bond network of BAEEH+·Cl− determined by x-ray diffraction. Disordered atoms and H atoms not involved in H-bonding were omitted for clarity reasons.
One layer of bonded ions through H-bonds.
(a) Bond length, (b) valence angle, and (c) torsion angle differences between experimental (x ray) and computed data from different models for conformer A (case referred to geometrical parameters not involving hydrogen atoms; see Fig. 2 for atom labeling).
FT-IR (top) and Raman (bottom) experimental spectra of solid BAEEH+·Cl− recorded at room temperature (a); B3LYP/6-31++G(d,p) simulated spectra in vacuo of BAEEH+ (b) and BAEEH+(H2O)5 complex (c) (calculated wavenumbers were scaled by a factor of 0.965; bands due to water were excluded for clarity); and vibrational frequencies from the solid-state model (d) (intensities are not provided by the CPMD code). The features indicated by arrows correspond to the following: : (νNH2 as.)Guan; : νNHGuan; : (νNH2 s.)Guan; : νNHAmide; : νCHRing; : νCH; : νC=OEster; : νC=OAmide; : δNHGuan; : νC–CRing; : δNHAmide, νC–NAmide; : νC–O–CEster as.; : ρNHGuan; : ρCHRing.
X-ray and calculated (PBC geometry optimization) data on the hydrogen-bonding related geometric parameters in the crystal of BAEEH+·Cl− (D: donor; A: acceptor). See Fig. 2 for atom numbering.
Observed IR data for BAEEH+·Cl− (polycrystalline sample pressed in a KBr pellet). The observed Raman data for BAEEH+·Cl− (pellet of neat polycrystalline sample) are presented in parentheses.
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