Synthesis, Crystal Structure, Hirshfeld Surface Analysis, and Computational Study of a Novel Organic Salt Obtained from Benzylamine and an Acidic Component

Synthesis and structural investigation of salts of 2-amino-3-methylpyridine with carboxylic acid derivatives: an experimental and theoretical study

The salts bis(2-amino-3-methylpyridinium) fumarate dihydrate, 2C6H9N2+·C4H2O22-·2H2O (I), and 2-amino-3-methylpyridinium 5-chlorosalicylate, C6H9N2+·C7H4ClO3- (II), were synthesized from 2-amino-3-methylpyridine with fumaric acid and 5-chlorosalicylic acid, respectively. The crystal structures of these salts were characterized by single-crystal X-ray diffraction, revealing protonation in I and II by the transfer of a H atom from the acid to the pyridine base. In the crystals of both I and II, N-H...O interactions form an R22(8) ring motif. Hirshfeld surface analysis distinguishes the interactions present in the crystal structures of I and II, and the two-dimensional (2D) fingerprint plot analysis shows the percentage contribution of each type of interaction in the crystal packing. The volumes of the crystal voids of I (39.65 Å3) and II (118.10 Å3) have been calculated and reveal that the crystal of I is more mechanically stable than II. Frontier molecular orbital (FMO) analysis predicts that the band gap energy of II (2.6577 eV) is lower compared to I (4.0035 eV). The Quantum Theory of Atoms In Molecules (QTAIM) analysis shows that the pyridinium-carboxylate N-H...O interaction present in I is stronger than the other interactions, whereas in II, the hydroxy-carboxylate O-H...O interaction is stronger than the pyridinium-carboxylate N-H...O interaction; the bond dissociation energies also confirm these results. The positive Laplacian [∇2ρ(r) > 0] of these interactions shows that the interactions are of the closed shell type. An in-silico ADME (Absorption, Distribution, Metabolism and Excretion) study predicts that both salts will exhibit good pharmacokinetic properties and druglikeness.

1D and 2D Coordination Polymers of Calcium with Nonsteroidal Anti-Inflammatory Drugs: Synthesis, Crystal Structures, Hirshfeld Surfaces, Antimicrobial and Antioxidant Activities

Four alkaline earth metal complexes of ketoprofen (Hket) and indomethacin (Hind) were synthesized and characterized: [Ca(ket)2(H2O)2]n (1), [Mg(ket)2(H2O)2] (2), [Ca(ind)2(EtOH)2]n (3), and [Mg(ind)2(EtOH)2] (4). All compounds were studied by elemental analysis (EA), flame atomic absorption spectrometry (FAAS), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Crystal structures of 1 and 3 were determined by single crystal X-ray diffraction technique T=100 K. The structure of 1 is dominated by a one-dimensional coordination polymer, while 3 is formed by a two-dimensional layer stabilized by the calcium zig-zag chains and π⋅⋅⋅π stacking interactions. Crystal packing arrangements were characterized by fingerprint plots (FPs) that were derived from the Hirshfeld surfaces (HSs). The antioxidant and antimicrobial activities of complexes were evaluated against Gram-positive and Gram-negative bacteria as well as yeasts.

Crystal structure, intermolecular interactions, charge-density distribution and ADME properties of the acridinium 4-nitrobenzoate and 2-amino-3-methylpyridinium 4-nitrobenzoate salts: a combined experimental and theoretical study

Acridines are a class of bioactive agents which exhibit high biological stability and the ability to intercalate with DNA; they have a wide range of applications. Pyridine derivatives have a wide range of biological activities. To enhance the properties of acridine and 2-amino-3-methylpyridine as the active pharmaceutical ingredient (API), 4-nitrobenzoic acid was chosen as a coformer. In the present study, a mixture of acridine and 4-nitrobenzoic acid forms the salt acridinium 4-nitrobenzoate, C13H10N+·C7H4NO4- (I), whereas a mixture of 2-amino-3-methylpyridine and 4-nitrobenzoic acid forms the salt 2-amino-3-methylpyridinium 4-nitrobenzoate, C6H9N2+·C7H4NO4- (II). In both salts, protonation takes place at the ring N atom. The crystal structure of both salts is predominantly governed by hydrogen-bond interactions. In salt I, C-H...O and N-H...O interactions form an infinite chain in the crystal, whereas in salt II, intermolecular N-H...O interactions form an eight-membered R22(8) ring motif. A theoretical charge-density analysis reveals the charge-density distribution of the inter- and intramolecular interactions of both salts. An in-silico ADME analysis predicts the druglikeness properties of both salts and the results confirm that both salts are potential drug candidates with good bioavailability scores and there is no violation of the Lipinski rules, which supports the druglikeness properties of both salts. However, although both salts exhibit drug-like properties, salt I has higher gastrointestinal absorption than salt II and hence it may be considered a potential drug candidate.

Preparation, Crystal Structure, Supramolecular Assembly, and DFT Studies of Two Organic Salts Bearing Pyridine and Pyrimidine

The effective preparation of two new pyrimidine- and pyridine-based organic crystalline salts with substituted acidic moieties (i.e., (Z)-4-(naphthalen-2-ylamino)-4-oxobut-2-enoic acid (DCNO) and 2-hydroxy-3,5-dinitrobenzoic acid (PCNP)) using methanol as a solvent has been reported. These molecular salts have ionic interactions that are responsible for their structural stabilization in their solid-state assemblies. The crystal structures of DCNO and PCNP were determined by the single-crystal X-ray diffraction (SCXRD) technique. The SCXRD study inferred that cations and anions are strongly packed due to N-H···O, N-H···N, and C-H···O noncovalent interactions in DCNO, whereas in PCNP, N-H···N noncovalent interactions are absent. The noncovalent interactions in both organic crystalline salts were comprehensively investigated by Hirshfeld surface analysis. Further, a detailed density functional theory (DFT) study of both compounds was performed. The optimized structures of both compounds supported the existence of the H-bonding and weak dispersion interactions in the synthesized organic crystalline salt structures. Both compounds were shown to have large and noticeably different HOMO/LUMO energy gaps. The atomic charge analysis results supported the SCXRD and HSA results, showing the formation of intermolecular noncovalent interactions in both organic crystalline salts. The results of the natural bond orbital (NBO) analysis confirmed the existence of (relatively weak) noncovalent interactions between the cation and anion moieties of their organic crystalline salts. The global reactivity parameters (GRPs) analysis showed that both organic crystalline salts' compounds should be quite thermodynamically stable and that DCNO should be less reactive than PCNP. For both compounds, the molecular electrostatic potential (MEP) analysis results support the existence of intermolecular electrostatic interactions in their organic crystalline salts.

Novel Indoline Spiropyrans Based on Human Hormones β-Estradiol and Estrone: Synthesis, Structure, Chromogenic and Cytotoxic Properties

The introduction of a switchable function into the structure of a bioactive compound can endow it with unique capabilities for regulating biological activity under the influence of various types of external stimuli, which makes such hybrid compounds promising objects for photopharmacology, targeted drug delivery and bio-imaging. This work is devoted to the synthesis and study of new spirocyclic derivatives of important human hormones-β-estradiol and estrone-possessing a wide range of biological activities. The obtained hybrid compounds represent an indoline spiropyrans family, a widely known class of organic photochromic compounds. The structure of the compounds was confirmed by ¹H and ¹³C NMR, IR, HRMS and single-crystal X-ray analysis. The intermolecular interactions in the crystals of spiropyran (3) were defined by Hirshfeld surfaces and 2D fingerprint plots, which were successfully acquired from CrystalExplorer (v21.5). All target hybrids demonstrated pronounced activity in the visible region of the spectrum. The mechanisms of thermal isomerization processes of spiropyrans and their protonated merocyanine forms were studied by DFT methods, which revealed the energetic advantage of the protonation process with the formation of a β-cisoid CCCH conformer at the first stage and its further isomerization to more stable β-transoid forms. The proposed mechanism of acidochromic transformation was confirmed by the additional NMR study data that allowed for the detecting of the intermediate CCCH isomer. The study of the short-term cytotoxicity of new spirocyclic derivatives of estrogens and their 2-formyl-precursors was performed on the HeLa cell model. The precursors and spiropyrans differed in toxicity, suggesting their variable applicability in novel anti-cancer technologies.

Efficient Synthesis of Imine-Carboxylic Acid Functionalized Compounds: Single Crystal, Hirshfeld Surface and Quantum Chemical Exploration

Two aminobenzoic acid based crystalline imines (HMBA and DHBA) were synthesized through a condensation reaction of 4-aminobenzoic acid and substituted benzaldehydes. Single-crystal X-ray diffraction was employed for the determination of structures of prepared Schiff bases. The stability of super molecular structures of both molecules was achieved by intramolecular H-bonding accompanied by strong, as well as comparatively weak, intermolecular attractive forces. The comparative analysis of the non-covalent forces in HMBA and DHBA was performed by Hirshfeld surface analysis and an interaction energy study between the molecular pairs. Along with the synthesis, quantum chemical calculations were also accomplished at M06/6-311G (d, p) functional of density functional theory (DFT). The frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), natural bond orbitals (NBOs), global reactivity parameters (GRPs) and natural population (NPA) analyses were also carried out. The findings of FMOs found that Egap for HMBA was examined to be smaller (3.477 eV) than that of DHBA (3.7933 eV), which indicated a greater charge transference rate in HMBA. Further, the NBO analysis showed the efficient intramolecular charge transfer (ICT), as studied by Hirshfeld surface analysis.

Structural and theoretical investigations, Hirshfeld surface analysis and anti-SARS CoV-2 of nickel (II) coordination complex

A nickel(II) Schiff base complex, [Ni(L)(DMF)](1), was synthesized by treating NiCl₂.6H₂O with an ONS-donor Schiff base ligand(H₂L) derived from the condensation 3,5-Dichlorosalicylaldehyde and 4,4-Dimethyl-3-thiosemicarbazide in DMF. The geometry around the center metal ion in [Ni(L)(DMF)](1) was square planar as revealed by the data collection from diffraction studies. DFT calculations were performed on the complex to get a structure-property relationship. Hirshfeld surface analysis was also carried out in the crystal structure of nickel (II) Schiff base complex. Additionally, inspiring from recent developments to find a potential inhibitor for SARS-CoV-2 virus, we have also performed molecular docking study of [Ni(L)(DMF)](1) to see if our novel complex show affinity for main protease (M^pro) of SARS-CoV-2 M^pro (PDB ID: 6LZE). Interestingly, the results are found quite encouraging where the binding affinity and inhibition constant was found to be -6.6 kcal/mol and 2.358 µM, respectively, for the best docked confirmation of complex [Ni(L)(DMF)](1) with M^pro protein. This binding affinity is reasonably well as compared to recently known antiviral drugs. For instance, the binding affinity of complex [Ni(L)(DMF)](1) is found to be better than that of recently docking results of anti-SARS-CoV-2 drugs like chloroquine (-6.293 kcal/mol), hydroxychloroquine (-5.573 kcal/mol) and remdesivir (-6.352 kcal/mol) when targeted to the active-site of SARS-CoV-2 M^pro. Besides this, molecular docking against G25K GTP-nucleotide binding protein (PDB ID: 1A4R) was also studied. We believe that current results can intrigue not only for the biomedical community but also for the materials chemists who are engaged to explore the application coordination complexes. Communicated by Ramaswamy H. Sarma.

Rational synthesis, biological screening of azo derivatives of chloro-phenylcarbonyl diazenyl hydroxy dipyrimidines/thioxotetrahydropyrimidines and their metal complexes

Herein, a new series of azo ligands HL-1 (5-(2-chloro-6-(phenylcarbonyl)phenyl)diazenyl)-6-hydroxydihydropyrimidines-2,4dione), HL-2 (5-(2-chloro-6-(phenylcarbonyl)phenyl)diazenyl)-6-hydroxy-2-thioxottetrahydropyrimidin-4one), HL-3 (5-(2,4-dichloro-6-(phenylcarbonyl)phenyl) diazenyl)-6-hydroxydihydropyrimidines-2,4dione), HL-4 (5-(2,4-dichloro-6-(phenylcarbonyl) phenyl)diazenyl)-6-hydroxy-2-thioxotetrahydropyrimidin-4one) and their metal complexes with Cu(II) & Ni(II) were synthesized successfully having excellent yield, in reproducible conditions and for structure elucidation different advance spectroscopic techniques (FTIR, ¹H NMR, ¹³C NMR and Mass Spectrometry) were applied. In FTIR analysis, the absence of peak at 3450-3550 cm ^-1 due to -NH₂ and presence of a new peak of N=N at 1390-1520 cm^-1 confirmed synthesis of the ligands. The ¹H NMR spectra of azo ligands showed singlet peak at 11.5-13.5 ppm (Ar-OH) for hydroxyl group and -NH₂ signals disappearance of anilines at 4-5 ppm also gives strong indication for the synthesis of azo compounds. On complexation two most important peaks (M-O, M-N) appeared in all the metal chelates in the range of 400-600 cm^-1 which were not present in any of the ligands, confirmed the formation of complexes. Molecular ion peaks in mass spectra at 273, 388, 407 and 423 m/z value for ligands as well as for complexes at 803, 835, 871 and 904 m/z also give strong indication that proposed ligands and their metal complexes are produced successfully. Biological screening of the synthesized compounds were also carried out against different bacterial strains (E.coli, S.typhi, and B.subtilis), antifungal (C.albicans, A.niger, and C.glabrata) strains and antioxidant activity. From results it was observed that HL-4 and Cu complexes exhibited maximum inhibition against all bacterial and fungal strains as compared to other ligands and standard drug.

Self-assembled mononuclear complexes: open metal sites and inverse dimension-dependent catalytic activity for the Knoevenagel condensation and CO2 cycloaddition

To lessen the greenhouse effect, measures such as improving the recovery of crude oil and converting carbon dioxide (CO₂) into valuable chemicals are necessary to create a sustainable low-carbon future. To this end, the development of efficient new oil-displacing agents and CO₂ conversion has aroused great interest in both academia and industry. The Knoevenagel condensation and CO₂ cycloaddition are the key reactions to solve the above problems. Four Cu- or Zn-based molecular complexes built from different ligands possessing hydrophilic-hydrophobic layers and different dimensionalities were chosen as solid catalysts for this study. Structural analysis revealed the presence of hydrophilic-hydrophobic layers and open metal sites in the low-dimensional complexes. To obtain deep insight into the reaction mechanism, first-principles density functional theory (DFT) calculations were carried out. These calculations confirmed that in the Knoevenagel condensation reaction, the final formation of benzylidenemalononitrile is the rate-determining step (an energy barrier (ΔE) value of 73.2 kJ mol^-1). The zero-dimensional (0D) Cu molecular complex with unsaturated metal centers, hydrophilic and hydrophobic layers, exhibited higher catalytic activity (yield: 100%, temperature: room temperature, and time: 2 h) compared with one- and two-dimensional Cu complexes. In the presence of a 0D Zn complex co-catalyzed with Br^- in the CO₂ cycloaddition reaction, the ΔE value reduces to 35.5 kJ mol^-1 for the ring opening of styrene oxide (SO), which is significantly lower than Br^- catalyzed (80.9 kJ mol^-1) reactions. The roles of unsaturated metal centers, hydrophilic-hydrophobic layers and dimensionality in the Knoevenagel condensation and CO₂ cycloaddition were explained in the results of structure-activity relationships.

Synthesis, Structural, and Intriguing Electronic Properties of Symmetrical Bis-Aryl-α,β-Unsaturated Ketone Derivatives

Three symmetrical bis-aryl-α,β-unsaturated ketone derivatives, 2,6-di((E)-benzylidene)-cyclohexan-1-one (DBC), 2,6-bis((E)-4-chlorobenzylidene)cyclohexan-1-one (BCC), and (1E,1'E,4E,4'E)-5,5'-(1,4-phenylene)bis(2-methyl-1-phenylpenta-1,4-dien-3-one) (PBMP), have been prepared using the aldol condensation approach toward ketones having two enolizable sites. The structures of DBC, BCC, and PBMP have been resolved via spectrometric methods. Moreover, the crystal structure of PBMP is determined by the single-crystal X-ray diffraction (SC-XRD) technique, which revealed that the PBMP molecular assembly is stabilized by the intermolecular C-H···O bonding and C-O···π and weak T-shaped offset π···π stacking interactions. The Hirshfeld surface analysis (HSA) of the PBMP crystal structure was performed as well, and the results were compared with the results of DBC and BCC. The density functional theory (DFT) study results revealed that the longer conjugated molecule of PBMP has smaller but still quite significant HOMO-LUMO gaps compared to the smaller molecules of BCC and DBC. The natural population analysis (NPA) and natural bonding orbital (NBO) analysis were performed. Accordingly, the hydrogen bonding and dipole-dipole interactions stabilize the crystal structures of these compounds. Additionally, the NBO analysis showed numerous high-energy stabilizing interactions for the PBMP compound due to the presence of numerous delocalized and relatively easily polarizable π-electrons, thus implying its significant thermodynamic stability. According to the global reactivity parameter (GRP) analysis, the compounds BCC and DBC are relatively stable in redox processes and have high thermodynamic stability and relatively lower reactivity in general. The molecular electrostatic potential (MEP) analysis results imply potential formation of the intermolecular hydrogen bonding and dispersion interactions, which stabilizes the crystal structures of these compounds.

Facile synthesis, crystal structure, biological evaluation, and molecular modeling studies of N-((4-acetyl phenyl) carbamothioyl) pivalamide as the multitarget-directed ligand

The crystal structure of N-((4-acetylphenyl)carbamothioyl)pivalamide (3) was synthesized by inert refluxing pivaloyl isothiocyanate (2) and 4-aminoacetophenone in dry acetone. The spectroscopic characterization (¹H-NMR, ¹³CNMR, FT-IR) and single crystal assays determined the structure of synthesized compound (3). Systematic experimental and theoretical studies were conducted to determine the molecular characteristics of the synthesized crystal. The biological examination of (3) was conducted against a variety of enzymes i.e., acetyl cholinesterase (AChE), butyl cholinesterase (BChE), alpha amylase, and urease enzyme were evaluated. The crystal exhibited approximately 85% enzyme inhibition activity against BChE and AChE, but only 73.8 % and 57.9% inhibition activity against urease and alpha amylase was observed respectively. The theoretical calculations were conducted using density functional theory studies (DFTs) with the 6–31G (d, p) basis set and B3LYP functional correlation. The Frontier molecular orbital analysis revealed that the HOMO/LUMO energy gap was smaller, which corresponds to the molecule’s reactivity. In terms of reactivity, the chemical softness value was found to be in good agreement with experimental values. In Crystal structure analysis, the intramolecular N—H•••O hydrogen bond generates a S 6) ring motif and N—H•••O interactions exist in crystal structure between the centroids of neighboring parallel aromatic (C4-C9) rings with a centroid to centroid distance of 3.9766 (7)Å. These intermolecular interactions were useful in structural stabilization. The Hirshfeld surfaces and their related two-dimensional fingerprint plots were used for thorough investigation of intermolecular interactions. According to Hirshfeld surface analysis of the crystal structure the most substantial contributions to the crystal packing are from H ••• O and H ••• N/N ••• H interactions. Molecular docking studies were conducted to evaluate the binding orientation of synthesized crystal with multiple targets. The compound exhibited stronger interactions with AChE and BChE with binding energies of -7.5 and -7.6 kcal/mol, respectively. On the basis of in-vitro and in-silico findings, it is deduced that N-((4-acetylphenyl)carbamothioyl)pivalamide 3) possesses reactive and potent multiple target inhibitory properties.

Exploring Highly Functionalized Tetrahydropyridine as a Dual Inhibitor of Monoamine Oxidase A and B: Synthesis, Structural Analysis, Single Crystal XRD, Supramolecular Assembly Exploration by Hirshfeld Surface Analysis, and Computational Studies

Ethyl 4-(4-fluorophenylamino)-2,6-bis(4-(trifluoromethyl)phenyl)-1-(4-fluoro-phenyl)-1,2,5,6-tetrahydropyridine-3-carboxylate (FTEAA) has been synthesized efficiently in an iodine-catalyzed five-component reaction of 4-fluoroaniline, 4-trifluoromethyl benzaldehyde, and ethyl acetoacetate in methanol at 55 °C for 12 h. Various spectro-analytical techniques such as ¹H and ¹³C NMR and Fourier-transform infrared spectroscopy have validated the structure of FTEAA. Further confirmation of the structure of FTEAA has been established on the basis of single-crystal X-ray diffraction analysis. The supramolecular assembly of FTEAA in terms of strong and comparatively weak noncovalent interactions is fully investigated by Hirshfeld surface analysis, the interaction energy between pairs of molecules, and energy frameworks. The void analysis is conducted to explore the strength and stability of the crystal structure. Furthermore, molecular docking analysis was computationally performed to see the potential intermolecular interactions between the selected proteins and FTEAA. The binding interaction energies are found to be -8.8 and -9.6 kcal/mol for the proteins MAO-B (PDB ID: 2V5Z) and MAO-A (PDB ID: 2Z5X), respectively. These reasonably good binding energies (more negative values) indicate the efficient associations between the FTEAA and target proteins. The proteins and FTEAA were also analyzed for intermolecular interactions. FTEAA and proteins interact in a variety of ways, like conventional hydrogen bonds, carbon-hydrogen bonds, alkyl, π-alkyl, and halide interactions.

Synthesis of Crystalline Fluoro-Functionalized Imines, Single Crystal Investigation, Hirshfeld Surface Analysis, and Theoretical Exploration

This investigation is focused on the synthesis of two halo-functionalized crystalline Schiff base (imine) compounds: (E)-2-methoxy-6-(((3-(trifluoromethyl)phenyl)imino)methyl)phenol (MFIP) and (E)-1-(((2-fluorophenyl)imino)methyl)naphthalen-2-ol (FPIN) by the condensation reaction of substituted benzaldehydes and substituted aniline. The crystal structures of MFIP and FPIN were determined unambiguously by single-crystal X-ray diffraction (SC-XRD) studies. Intermolecular interactions and the role of fluorine atoms in the stabilization of the crystal packing are explored for both compounds using Hirshfeld surface analysis. Accompanied with experimental studies, quantum chemical calculations were also performed for comprehensive structure elucidation at the M06/6-311G(d,p) level of theory. A comparison of experimental and density functional theory results for geometrical parameters exhibited excellent agreement. Interestingly, Frontier molecular orbitals and natural bond orbital (NBO) findings revealed that intramolecular charge transfer and hyper-conjugation interactions had played a significant role to stabilize the molecules. Both compounds exhibited a relatively larger value of hardness with a smaller global softness, which, as proposed by the SC-XRD and NBO study, shows a higher stability. Nonlinear optical (NLO) findings showed that FPIN manifested a larger value of linear polarizability (<a> = 293.06 a.u.) and second-order hyperpolarizability (<γ> = 3.31 × 10⁵ a.u.) than MFIP (<a> = 252.42 and <γ> = 2.08 × 10⁵ a.u.) due to an extended conjugation. The above-mentioned findings of the entitled compounds may play a crucial role in NLO applications.

Shedding Light on the Synthesis, Crystal Structure, Characterization, and Computational Study of Optoelectronic Properties and Bioactivity of Imine derivatives

Two imine compounds named as (E)-2-(((3,4-dichlorophenyl)imino)methyl)phenol (DC2H) and (E)-4-(((2,4-dimethylphenyl)imino)methyl)phenol (DM4H) are synthesized, and their crystal structures are verified using the single-crystal X-ray diffraction (XRD) technique. The crystal structures of the compounds are compared with the closely related crystal structures using the Cambridge Structural Database (CSD). The crystal packing in terms of intermolecular interactions is fully explored by Hirshfeld surface analysis. Void analysis is carried out for both compounds to check the strength of the crystal packing. Furthermore, a state-of-the-art dual computational technique consisting of quantum chemical and molecular docking methods is used to shed light on the molecular structure, optoelectronic properties, and bioactivity of indigenously synthesized compounds. The optimized molecular geometries are compared with their counterpart experimental values. Based on previous reports of biofunctions of the indigenously synthesized imine derivatives, they are explored for their potential inhibition properties against two very crucial proteins (main protease (M^pro) and nonstructural protein 9 (NSP9)) of SARS-CoV-2. The calculated interaction energy values of DC2H and DM4H with M^pro are found to be -6.3 and -6.6 kcal/mol, respectively, and for NSP9, the calculated interaction energy value is found to be -6.5 kcal/mol. We believe that the current combined study through experiments and computational techniques will not only pique the interest of the broad scientific community but also evoke interest in their further in vitro and in vivo investigations.

Single-Crystal Investigation, Hirshfeld Surface Analysis, and DFT Study of Third-Order NLO Properties of Unsymmetrical Acyl Thiourea Derivatives

In the current research work, unsymmetrical acyl thiourea derivatives, 4-((3-benzoylthioureido)methyl)cyclohexane-1-carboxylic acid (BTCC) and methyl 2-(3-benzoylthioureido)benzoate (MBTB), have been synthesized efficiently. The structures of these crystalline thioureas were unambiguously confirmed by single-crystal diffractional analysis. The crystallographic investigation showed that the molecular configuration of both compounds is stabilized by intramolecular N-H···O bonding. The crystal packing of BTCC is stabilized by strong N-H···O bonding and comparatively weak O-H···S, C-H···O, C-H···π, and C-O···π interactions, whereas strong N-H···O bonding and comparatively weak C-H···O, C-H···S, and C-H···π interactions are responsible for the crystal packing of MBTB. The noncovalent interactions that are responsible for the crystal packing are explored by the Hirshfeld surface analysis for both compounds. The void analysis is performed to find the quantitative strength of crystal packing in both compounds. Additionally, state-of-the-art applied quantum chemical techniques are used to further explore the structure-property relationship in the above-entitled molecules. The optimization of molecular geometries showed a reasonably good correlation with their respective experimental structures. Third-order nonlinear optical (NLO) polarizability calculations were performed to see the advanced functional application of entitled compounds as efficient NLO materials. The average static γ amplitudes are found to be 27.30 × 10^-36 and 102.91 × 10^-36 esu for the compounds BTCC and MBTB, respectively. The γ amplitude of MBTB is calculated to be 3.77 times larger, which is probably due to better charge-transfer characteristics in MBTB. The quantum chemical analysis in the form of 3-D plots was also performed for their frontier molecular orbitals and molecular electrostatic potentials for understanding charge-transfer characteristics. We believe that the current investigation will not only report the new BTCC and MBTB compounds but also evoke the interest of the materials science community in their potential use in NLO applications.