6-methoxy-8-[[6-methoxy-8-[[6-methoxy-2-methyl-1-(2-methylpropyl)-3,4-dihydro-1h-isoquinolin-7-yl]oxy]-2-methyl-1-(2-methylpropyl)-3,4-dihydro-1h-isoquinolin-7-yl]oxy]-2-methyl-1-(2-methylpropyl)-3,4-dihydro-1h-isoquinolin-7-ol time-resolved absorption and resonance ft-ir and raman biospectroscopy and density functional theory (dft) investigation of vibronic-mode coupling structure in vibrational spectra analysis

6-methoxy-8-[[6-methoxy-8-[[6-methoxy-2-methyl-1-(2methylpropyl)-3,4-dihydro-1h-isoquinolin-7-yl]oxy]-2-methyl-1(2-methylpropyl)-3,4-dihydro-1h-isoquinolin-7-yl]oxy]-2-methyl1-(2-methylpropyl)-3,4-dihydro-1h-isoquinolin-7-ol time-resolved absorption and resonance ft-ir and raman biospectroscopy and density functional theory (dft) investigation of vibronic-mode coupling structure in vibrational spectra analysis


Introduction
A macromolecule is a very large molecule, such as protein, commonly created by the polymerization of smaller subunits (monomers). They are typically composed of thousands of atoms or more. The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, carbohydrates and lipids) and large non-polymeric molecules (such as lipids and macrocycles). Synthetic macromolecules include common plastics and synthetic fibers as well as experimental materials such as carbon nanotubes. Density Functional Theory (DFT) is one of the most powerful calculation methods for electronic structures [5][6][7]. Numerous results have been previously studied and indicate successful use of these methods [8][9][10]. The theory is one of the most appropriate methods for simulating the vibrational wavenumbers, molecular structure as well as total energy. It may be useful to initially consider the calculated results by density functional theory using HF/6-31G * , HF/6-31++G ** , MP2/6-31G, MP2/6-31++G ** , BLYP/6-31G, BLYP/6-31++G ** , B3LYP/6-31G and B3LYP6-31-HEG ** approach [11][12][13][14][15][16]. It should be noted that calculations are performed by considering one degree of quantum interference as well as polarization effects of 2d orbitals in interaction .

Details of Calculations
All calculations of molecular orbital in the base of ab are performed by Gaussian 09. In calculation process, the structure of 6-Methoxy  (Figure 1) is optimized and FT-IR and Raman wavenumbers are calculated using HF/6-31G * , HF/6-31++G ** , MP2/6-31G, MP2/6-31++G ** , BLYP/6-31G, BLYP/6-31++G ** , B3LYP/6-31G and B3LYP6-31-HEG ** base. All optimized structures are adjusted with minimum energy. Harmonic vibrational wavenumbers are calculated using second degree of derivation to adjust convergence on potential surface as good as possible and to evaluate vibrational energies at zero point. In optimized structures considered in the current study, virtual frequency modes are not observed which indicates that the minimum potential energy surface is correctly chosen. The optimized geometry is calculated by minimizing the energy relative to all geometrical quantities without forcing any constraint on molecular symmetry. Calculations were performed by Gaussian 09. The current calculation is aimed to maximize structural optimization using density functional theory. The calculations of density functional theory are performed by HF/6-31G * , HF/6-31++G ** , MP2/6-31G, MP2/6-31++G ** , BLYP/6-31G, BLYP/6-31++G ** , B3LYP/6-31G and B3LYP6-31-HEG ** function in which non-focal functions of Becke and correlation functions of Lee-Yang-Parr beyond the Franck-Condon approximation are used. After completion of optimization process, the second order derivation of energy is calculated as a function of core coordination and is investigated to evaluate whether the structure is accurately minimized. Vibrational frequencies used to simulate spectrums presented in the current study are derived from these second order derivatives. All calculations are performed for room temperature of 508 (K).
C-H stretching vibrations in single replacement of benzene cycles are usually seen in band range of 3000-4000 cm -1 . Weak Raman bands are at 3193 cm -1 and 3207 cm -1 . C-C stretching mode is a strong Raman mode at 1211cm -1 . Raman weak band is seen at 1667 cm -1 , too. Bending mode of C-H is emerged as a weak mode at 1388 cm -1 and 1187 cm -1 and a strong band at 1291 cm -1 in Raman spectrum. Raman is considerably active in the range of 1000-2000 cm -1 which 1189 cm -1 indicates this issue.
C-H skew-symmetric stretching mode of methylene group is expected at 3199 cm -1 and its symmetric mode is expected at 3001 cm -1 . Skew-symmetric stretching mode of CH 2 in 6-Methoxy-8- -Isoquinolin-7-ol has a mode in mid-range of Raman spectrum at 3000-3530 cm -1 . When this mode is symmetric, it is at 3098 cm -1 and is sharp. The calculated wavenumbers of higher modes are at 3064 cm -1 and 3098 cm -1 for symmetric and skew-symmetric stretching mode of methylene, respectively.
Scissoring vibrations of CH 2 are usually seen at the range of 1528-1589 cm -1 which often includes mid-range bands. Weak bands at 1555 cm -1 are scissoring modes of CH 2 in Raman spectrum. Moving vibrations of methylene are usually seen at 1473 cm -1 . For the investigated chemical in the current study, these vibrations are at 1341 cm -1 were calculated using density functional theory. Twisting and rocking vibrations of CH 2 are seen in Raman spectrum at 900 cm -1 and 1200 cm -1 , respectively, which are in good accordance with the results at 915 cm -1 and 1185 cm -1 , respectively.
In a non-ionized carboxyl group (COOH), stretching vibrations of carbonyl [C=O] are mainly observed at the range of 1880-11890 cm -1 . If dimer is considered as an intact constituent, two stretching vibrations of carbonyl for symmetric stretching are at 1765-1795 cm -1 in Raman spectrum. In the current paper, stretching vibration of carbonyl mode is at 1803 cm -1 which is a mid-range value.
Stretching and bending bands of hydroxyl can be identified by width and band intensity which in turn is dependent on bond length of Hydrogen. In dimer form of Hydrogen bond, stretching band of O-H is of a strong Raman peak at 1387 cm -1 which is due to in-plain metamorphosis mode. Out-of-plain mode of O-H group is a very strong mode of peak at 1056 cm -1 of Raman spectrum. The stretching mode of C-O (H) emerges as a mid-band of Raman spectrum at 1267 cm -1 .
Lattice vibrations are usually seen at the range of 0-800 cm -1 .