FT-IR, FT-Raman and NMR characterization of 2-isopropyl-5-methylcyclohexyl quinoline-2-carboxylate and investigation of its reactive and optoelectronic properties by molecular dynamics simulations and DFT calculations

Highlights

• The rings PhI and PhIII are nearly planar while the cyclohexyl ring and carbonyl group are tilted from each other.

• The ring breathing mode of the phenyl ring is assigned at 1087 cm⁻¹.

• An extensive quantum chemical study of the title compound is reported.

• Reactive properties have been assessed through calculations of bond dissociation energies and radial distribution functions.

• Molecular docking suggests that the title compound might exhibit inhibitory activity against CDK inhibitors.

Abstract

The FT-IR and FT-Raman spectra of the synthesized compound, 2-isopropyl-5-methylcyclohexyl quinoline-2-carboxylate is recorded and analyzed. Optimized molecular structure, wave numbers, corresponding assignments regarding 2-isopropyl-5-methylcyclohexyl quinoline-2-carboxylate has become screened tentatively as well as hypothetically using Gaussian09 program package. Natural bonding orbital assessment has been completed with a reason to clarify charge transfer or conjugative interaction, the intra-molecular re-hybridization and delocalization of electron density within the molecule. The NMR spectral assessment had been made choosing structure property relationship by chemical shifts along with the magnetic shielding effects regarding the title compound. The first and second hyperpolarizabilities were calculated. The calculated first order hyperpolarizability is commensurate with the documented worth of very similar derivatives and could be an interesting object for more experiments on nonlinear optics. Local reactivity properties have been investigated using average local ionization energies and Fukui functions. Investigation of optoelectronic properties encompassed calculations of reorganization energies and hopping rates of charge carriers within the framework of Marcus semi-empiric approach. The docked ligand title compound forms a stable complex with CDK inhibitors and gives a binding affinity value of −9.7 kcal/mol and molecular docking results suggest that the compound might exhibit inhibitory activity against CDK inhibitors.

Introduction

Quinoline is characterized by a double ring structure composed of a benzene and a pyridine ring fused at two adjacent carbon atoms [1]. Methylcyclohexane is a monosubstituted cyclohexane, which has one branching via the attachment of one methyl group on one carbon atom of the cyclohexane ring and the lowest form of this monosubstituted methylcyclohexane occurs when the methyl group occupies an equatorial rather than an axial position [2]. Quinoline derivatives are well known for their nonlinear optical properties [3], [4] and invite much interest due to their great potent application in the field of organic light emitting diodes (OLEDs) [5], [6], [7], [8] and are used as dopants in the polymer LED materials [9]. Certain quinoline derivatives could generate a sharp green electroluminescence and a high quantum efficiency of emission in the blue and green region [10], [11], [12], [13]. Quinoline derivatives are well known for anti-amoebic, antiviral, anti-parasitic, anti-microbial and anti-tubercular activities and possess anti-proliferative, anti-neoplastic, and cytotoxic properties [14], [15], [16], [17]. Substituted quinoline derivatives possess a broad range of bioactivities such as anticancer, anti-malarial, antibiotic, antihypertensive, platelet-derived growth factor-receptors tyrosine kinase (PDGF-RTK) inhibition, DNA-intercalating carrier, anti-inflammatory, analgesic, anti-HIV, anti-tumour, DNA binding capability and many other functional material [18], [19], [20], [21]. A series of tetracyclic indenoquinolines is used as potential anticancer agents. The compounds, which are obtained through the photo isomerization of Diels–Alder adducts formed between purpurogallin derivatives and nitrosobenzene, have in vitro anti-proliferative activities against breast (MCF-7), lung epithelial (A-549) and cervical (HeLa) adenocarcinoma cells [22]. Several novel functionalized quinolones, which exhibited potential antineoplastic activity against eukaryotic type II topoisomerases [23]. In addition to the antibacterial quinolones, specific members of this drug family display high activity against eukaryotic type II topoisomerases, as well as cultured mammalian cells and invivo tumour models. These antineoplastic quinolones represent an exploitable source of new anticancer agents which might also help addressing undesirable-toxicity and resistance phenomena [23], [24]. Jayashree et al. [25] reported the molecular docking experiments of 4-oxotheino [3,2-c]quinoline-2-carboxylates with DNA and their potential anticancer property. The author's group reported the vibrational spectroscopic studies of a number of quinoline derivatives [26], [27], [28], [29], [30], [31]. The crystal structure of the title compound, C₂₀H₂₅NO₂ is reported Fazal et al. [32]. The present study carries out the vibrational spectral analysis of the title compound, 2-isopropyl-5-methylcyclohexyl quinoline-2-carboxylate (EF3) to elucidate the correlation amongst the molecular structure and prediction of normal modes. The redistribution of electron density in various bonding and antibonding orbitals along with stabilization energies have been calculated by natural bond orbital analysis to give clear proof of stabilization originating from hyper-conjugation of a variety of intra-molecular interaction. NMR spectra were also reported both experimentally and theoretically. The nonlinear optical properties and global chemical descriptors are also reported. Average local ionization energy maps (ALIE), bond dissociation energies (BDE) and radial distribution functions (RDF) are also reported in the present work.