scholarly journals DFT study of species derived from the narcotic antagonist naloxone

2020 ◽  
Vol 10 (2) ◽  
pp. 5096-5116
Keyword(s):  
Force Fields ◽  
Normal Modes ◽  
Tropane Alkaloids ◽  
Solvation Energy ◽  
Basis Set ◽  
Free Base ◽  
Harmonic Force ◽  
Energy Value ◽  
Vibrational Assignments ◽  
Solvation Energies

The functional hybrid B3LYP and the 6-31G* basis set have been employed to study the theoretical structures of free base, cationic and hydrochloride species of naloxone in gas phase and in aqueous solution. The SCRF methodology and the PCM method were used to optimize the species in solution while the solvation energies were computed with the universal solvation model. The harmonic force fields of three species in the two media were computed with the SQMFF methodology and the Molvib program while the complete vibrational assignments of bands observed in the experimental available ATR and Raman spectra were performed by using the harmonic force fields and the normal internal coordinates. Therefore, the expected 129, 132 and 135 vibration normal modes for the free base, cationic and hydrochloride species of naloxone, respectively are here reported. The free base of naloxone evidence the higher solvation energy value, as compared with those reported for S(-)-promethazine, R(+)-promethazine, cyclizine, morphine, cocaine, scopolamine, heroin, and tropane alkaloids. The cationic species shows a solvation energy value (-302.45 kJ/mol) closer to observed for morphine (-309.19 kJ/mol) while the value for the hydrochloride species (-122.28 kJ/mol) is near to scopolamine value (-122.74 kJ/mol). AIM analyses show ionic characteristic of N-HCl bonds in the hydrochloride species and suggest that this species in both media is as cationic one, as supported by the positive MK charges on the N5 atoms in the hydrochloride species in both media and by the absence in the ATR spectrum of band at 2405 cm-1, associated to N5-H46 stretching mode. Moreover, frontier orbitals studies evidence that the allyl chains present in the three species of naloxone diminishing the gap values increasing their reactivities, as compared with the other species containing the N-CH3 group. The f(N-H) force constants for the hydrochloride species is lower than the corresponding in solution, a result also observed for morphine (2.73 and 4.61 mdyn Å-1), cocaine (3.23 and 4.79 mdyn Å-1) and tropane (2.70 and 4.69 mdyn Å-1) alkaloids. Comparisons between experimental infrared, Raman and ultraviolet-visible spectra with the corresponding predicted show good correlations.

The vibrational spectra (100–1500 cm−1) of a series of bicyclo[3.2.1]octanes assigned by means of scaled 3-21G ab initio harmonic force fields

1993 ◽  
Vol 71 (4) ◽  
pp. 578-609 ◽  
Author(s):  
Thomas Eggimann ◽  
Nan Ibrahim ◽  
R. Anthony Shaw ◽  
Hal Wieser
Keyword(s):  
Ab Initio ◽  
Vibrational Spectra ◽  
Force Fields ◽  
Basis Set ◽  
Average Error ◽  
Field Scale ◽  
Harmonic Force ◽  
First Time ◽  
Derivatives Of ◽  
Phase Spectra

The infrared absorption (vapor phase and solution) and Raman (liquid phase) spectra of bicyclo[3.2.1]octane, 8-oxabicyclo[3.2.1]octane, 6-oxabicyclo[3.2.1]octane, 6,8-dioxabicyclo[3.2.1]octane, and the 7,7-dideutero-substituted derivatives of the last two compounds are reported in the region 100–1500 cm−1 for the first time. The vibrational spectra are assigned almost completely with the guidance of ab initio 3-21G geometries and scaled force fields. A total of 14 force-field scale facors are transferred from smaller molecules, predicting the frequencies with an average error of 7.6 cm−1 (1.2%) for 196 assigned transitions. After optimizing the factors in an overlay refinement involving all six molecules, the frequencies are within 5.7 cm−1 (0.75%) of experiment. The ab initio absorption and Raman intensities are calculated with the 3-21G basis set and are demonstrated to be of such accuracy as to be useful for the spectral assignments. These intensities are calculated with uniformly and nonuniformly scaled force fields and compared to the experimental spectra. The intensities derived from the latter force fields are superior, meaning that nonuniform scaling is preferable at this level of theory for both vibrational frequencies and normal mode descriptions.

scholarly journals Theoretical investigation of the Anti-Parkinson drug rasagiline and its salts: conformations and infrared spectra

2012 ◽  
Vol 10 (2) ◽  
pp. 395-406 ◽  
Author(s):  
U. Başköse ◽  
Sevgi Bayarı ◽  
Semran Sağlam ◽  
Hacı Özışık
Keyword(s):  
Density Functional ◽  
Single Point ◽  
Normal Modes ◽  
Basis Set ◽  
Stable Conformer ◽  
Functional Theory ◽  
Point Energy ◽  
Vibrational Assignments ◽  
B3lyp Method ◽  
The Density Functional Theory

AbstractThe conformational analysis of rasagiline [N-propargyl-1(R)-aminoindan] was performed by the density functional theory (DFT) B3LYP method using the 6–31++G (d,p) basis set. A single point energy calculations based on the B3LYP optimized geometries were also performed at MP2/6-31++G (d, p) level. The vibrational frequencies of the most stable conformer of rasagiline was calculated at the B3LYP level and vibrational assignments were made for normal modes on the basis of scaled quantum mechanical force field (SQM) method. The influence of mesylate and ethanedisulfonate salts on the geometry of rasagiline free base and its normal modes are also discussed.

scholarly journals Vibrational Studies of Species Derived from Potent S(+) and R(-) Ecstasy Stimulant by Using Ab-initio Calculations and the SQM Approach

2020 ◽  
Vol 10 (6) ◽  
pp. 6783-6809
Keyword(s):  
Chemical Shifts ◽  
Attenuated Total Reflectance ◽  
Free Base ◽  
1H And 13C Nmr ◽  
Vibrational Assignments ◽  
Solvation Energies ◽  
Deformation Modes ◽  
Aim And Nbo ◽  
Ir Bands ◽  
Ft Raman

B3LYP/6-311++G** calculations and the scaled quantum mechanical force field (SQMFF) approach have been used to study the structures and vibrational spectra of three species derived from potent S(+) and R(-) ecstasy stimulant. The complete vibrational assignments of free base, cationic, and hydrochloride species of both enantiomeric forms of ecstasy have been reported by using the normal internal coordinates and the experimental available attenuated total reflectance ATR-IR and FT-Raman spectra. SQM calculations predicted that the three species could be present in the IR spectrum of hydrochloride species because the IR bands of medium intensity at 2794 cm-1 is assigned to the stretching C4-H15 and symmetric CH3 modes of the free base while the strong IR band at 1508 cm-1 is assigned easily to NH2 stretching mode of hydrochloride species and NH2 deformation modes of cationic species. The calculations reveal the same energy values for both enantiomers, indicating that both could exist simultaneously in the two media with similar corrected solvation energies in solution probably because the R(-) form is quickly converted to the S(+) one. Three types of charges studied in both media evidence higher effect on the N atoms belonging to N-CH3 groups of three species of S(+) form of ecstasy in both media than on the O atoms of R1 ring. The high gap value predicted for the hydrochloride species of S(+) form in solution supports the low reactivity of this species, in agreement to its higher stability evidenced in this medium by AIM and NBO calculations. The predicted Ultraviolet-visible and Electronic Circular Dichroism ecstasy (ECD) support the presence of both enantiomeric forms in solution while excellent concordance evidence the comparisons between the predicted 1H- and 13C-NMR chemical shifts for the three species of S(+) form of ecstasy with the corresponding experimental ones.

Spectroscopic calculations on phosphorus and arsenic tricyanides: harmonic force fields, mean amplitudes of vibration and vibrational assignments

1973 ◽  
Vol 17 (2) ◽  
pp. 371-375 ◽  
Author(s):  
S.J. Cyvin ◽  
Signe Kjelstrup Ratkje ◽  
V. Devarajan ◽  
V.Unnikrishnan Nayar ◽  
G. Aruldhas
Keyword(s):  
Force Fields ◽  
Harmonic Force ◽  
Mean Amplitudes Of Vibration ◽  
Vibrational Assignments

scholarly journals Structural Study and Vibrational Assignments of Anticonvulsant Topiramate by using DFT calculations and Two Harmonic Force Fields

2020 ◽  
Vol 11 (3) ◽  
pp. 9880-9903
Keyword(s):  
Aqueous Solution ◽  
Gas Phase ◽  
Force Fields ◽  
Solid Phase ◽  
Reaction Force ◽  
Boat Conformation ◽  
Harmonic Force ◽  
1H And 13C Nmr ◽  
Vibrational Assignments ◽  
First Time

B3LYP/6-311++G** calculations have been combined with the scaled quantum mechanical force field (SQMFF) methodology to study structural and vibrational properties of anticonvulsant topiramate (TPM) agent. The 123 vibration modes expected for TPM were completely assigned, considering two harmonic force fields. In one case, C2V symmetries were considered for both SO2 and NH2 groups, while in the other one C2V and C3V symmetries for the NH2 and SO3 groups, respectively. The calculated harmonic vibrational frequencies are consistent with the experimental IR and Raman spectra in the solid phase. Very good concordances were found between the theoretical structures in gas phase and aqueous solution and the corresponding experimental reported. Thus, the fused five-membered ring in TPM produces that the pyranose ring adopts distorted twist-boat conformation, as was experimentally observed. In solution, all calculations were performed with the self-consistent reaction force (SCRF) method by the integral equation formalism variant polarised continuum (IEFPCM) and universal solvation model density (SMD) models. The corrected solvation energy value for TPM in aqueous solution by total non-electrostatic terms and by ZPVE is -1066.10 kJ/mol. The bond orders have evidenced that the three O atoms are not linked of the same form to S atom. Hence, the S atom of TPM is practically tetra-coordinate in both media, as evidenced by the high negative MK and NPA charges on the O atoms linked to it. The AIM study supports the higher stability of TPM in the gas phase while the NBO calculations suggest higher stability in solution. Gap values support the higher reactivity of TPM in solution than in the gas phase. The scaled force constant for both cases are reported for the first time. Comparisons of predicted 1H- and 13C-NMR spectra with the corresponding experimental ones reveal very good concordances.

Synthesis, Conformational Analysis, Infrared, Raman and UV-Visible Spectra of Novel Schiff Bases compiled with DFT Calculations

2020 ◽  
Vol 23 (7) ◽  
pp. 568-586
Author(s):  
Samy M. Ahmed ◽  
Ibrahim A. Shaaban ◽  
Elsayed H. El-Mossalamy ◽  
Tarek A. Mohamed
Keyword(s):  
Schiff Bases ◽  
1H Nmr ◽  
Electronic Absorption Spectra ◽  
Chemical Shifts ◽  
Basis Set ◽  
Oh Groups ◽  
Vibrational Assignments ◽  
Cartesian Coordinate ◽  
Surface Scan ◽  
Ir And Raman

Objective: Two novel Schiff bases named, 2-((2-Hydroxybenzylidene)amino)-4,5,6,7- tetrahydrobenzo[b] thiophene-3-carbonitrile (BESB1) and 2-((Furan-2-ylmethylene)amino)-4,5,6, 7-tetrahydro-benzo[b]thiophene-3-carbonitrile (BESB2) were synthesized. Methods: The structures were characterized based on CHN elemental analysis, mid-infrared (400– 4000 cm-1), Raman (100-4000 cm-1), 1H NMR, mass and UV-Vis spectroscopic measurements. In addition, quantum mechanical calculations using DFT-B3LYP method at 6-31G(d) basis set were carried out for both Schiff bases. Initially, we have carried out complete geometry optimizations followed by frequency calculations for the proposed conformational isomers; BESB1 (A–E) and BESB2 (F–J) based on the orientations of both CN and OH groups against the azomethine lonepair (NLP) in addition to the 3D assumption. Results: The computational outcomes favor conformer A for BESB1 in which the C≡N and OH moieties are cis towards the NLP while conformer G is preferred for BESB2 (the C≡N/furan-O are cis/trans towards the NLP) which was found consistent with the results of relaxed potential energy surface scan. Aided by normal coordinate analysis of the Cartesian coordinate displacements, we have suggested reliable vibrational assignments for all observed IR and Raman bands. Moreover, the electronic absorption spectra for the favored conformers were predicted in DMSO solution using TD-B3LYP/6-31G(d) calculations. Similarly, the 1H NMR chemical shifts were also estimated using GIAO approach implementing PCM including solvent effects (DMSO-d6). Conclusion: Proper interpretations of the observed electronic transition, chemical shifts, IR and Raman bands were presented in this study.

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