Synthesis,Crystal Structure,Spectroscopic, Electrochemical and Antimicrobial Properties of Cu(II) Complex with the Mixed Ligands of 2,9‐Dimethyl‐1,10‐phenanthroline and 4‐Hydroxypyridine‐2,6‐dicarboxylic Acid

A mononuclear Cu(II) complex with mixed ligands, formulated as [Cu(hypydc)(dmp)]·H₂O (hypydc=4‐hydroxypyridine‐2,6‐dicarboxylate, dmp=2,9‐dimethyl‐1,10‐phenanthroline), was synthesized and well characterized by single crystal X‐ray diffraction analysis, as well as spectroscopic (IR, UV‐Vis), and electrochemical methods. The Cu(II) atom exhibits a distorted square‐pyramidal geometry. Intermolecular O? H···O and C? H···O hydrogen bonds, π‐π stacking interactions and C? H···π interactions seem to be effective in the stabilization of the crystal structure. The complex was also evaluated for its antimicrobial activity using in vitro microdilution methods. Six standard bacteria and a strain of Candida albicans were used for the antimicrobial activities. There was a very strong activity against Candida albicans and significant activities against Enterococcus fecalis, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus, indicating important biological activities of the complex.     

Synthesis,characterization, crystal structure and biological activities of supramolecular compounds of Mn(II) and Zn(II) with dipicolinic acid and 8-hydroxyquinoline

Two compounds, (8-H₂Q)₂[Mn(dipic)₂] · 6H₂O (1) and (8-H₂Q)₂[Zn(dipic)₂] · 6H₂O (2) (8-HQ = 8-hydroxyquinoline (oxine), H₂dipic = dipicolinic acid), have been prepared and characterized by elemental, spectroscopic (IR and UV–Vis), and thermal analyses, magnetic measurements and single crystal X-ray diffraction techniques. Compounds 1 and 2 consist of two 8-hydroxyquinolinium cations, one bis(dipicolinato)M(II) anion (M = Mn(II) and Zn(II)) and six uncoordinated water molecules. Both 1 and 2 crystallize in the monoclinic space group C2/c. In the complex anion, each dipic ligand is tridentate through N of pyridine and oxygens of the carboxylate groups. Crystal packing of 1 and 2 is a composite of intermolecular hydrogen bonding interactions. The in vitro antibacterial and antifungal activities of 1 and 2 were evaluated by the agar well diffusion method by MIC (Minimal Inhibition Concentration), looking for compounds which display high-inhibitory effect against gram positive bacteria and fungi. No growth inhibition was observed against tested gram negative bacteria.     

Structurally characterized dinuclear zinc(II) bis(salamo)‐type tetraoxime complex possessing square pyramidal and trigonal bipyramidal geometries

A novel dinuclear Zn(II) complex with the chemical formula [Zn₂(L)(OCH₃)] has been synthesized by a bis(salamo)‐type tetraoxime ligand based on 3‐bromo‐5‐chlorosalicylicaldehyde, and characterized by elemental analyses, IR, UV–vis, and fluorescent spectra, and single‐crystal X‐ray diffraction analysis. All the Zn(II) atoms are pentacoordinated by N₂O₂ donor atoms from the (L)³⁻ unit and one oxygen atom from one μ₂‐methoxyl group. The Zn(II) (Zn1 and Zn4) atoms have distorted square pyramidal geometries (τ₁ = 0.458, τ₄ = 0.388), whereas the Zn2 and Zn3 atoms adopt trigonal bipyramidal (τ₂ = 0.675, τ₃ = 0.550) geometries. The Zn(II) complex is self‐assembled by intermolecular C H···O interactions to form an infinite three‐dimensional supramolecular structure. Interestingly, the intermolecular C H···π interactions in the Zn(II) complex is involved not in the formation of three‐dimensional structures but rather in the formation of the 0D dimer structure. Meanwhile, the optical properties of the Zn(II) complex were also measured and are discussed.     

Synthesis,crystal structure,DNA-binding properties,and antioxidant activity of a V-shaped ligand bis(N-methylbenzimidazol-2-ylmethyl)benzylamine and its zinc(II) complex

A V-shaped ligand bis(N-methylbenzimidazol-2-ylmethyl)benzylamine (L) and its zinc(II) complex, [ZnL ₂](pic)₂?·?2CH₃CN (pic?=?picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal X-ray crystallographic analysis revealed that the Zn(II) complex possesses a distorted trigonal bipyramidal geometry. Supramolecular interactions arising from various intra- or intermolecular π···π stacking interactions contributed to the form of the multidimensional configuration. Interactions of L and Zn(II) complex with DNA were monitored using spectrophotometric methods and viscosity measurements. The results suggest that L and Zn(II) complex both bind to DNA via intercalation and Zn(II) complex binds to DNA more strongly than L. Moreover, the Zn(II) complex also exhibited potential antioxidant properties in vitro.     

Chemical and spectroscopic studies of a new palladium(II) complex with N -acetyl-L-cysteine

Chemical and spectroscopic studies of a new palladium(II) N-acetyl-L-cysteine complex are described. Elemental analyses for the solid complex are consistent with the formula [Pd(C₅H₈NO₃S)₂]?·?H₂O or [Pd(NAC)₂]?·?H₂O. Solid-state ¹³C nuclear magnetic resonance (NMR), UV–Visible (UV–Vis) and infrared (IR) spectroscopic analyses are consistent with coordination of the ligand to palladium(II) through the nitrogen and sulfur atoms in a square-planar geometry. Thermogravimetric and differential thermal analyses confirmed the composition; final residue was identified as metallic palladium.     

Investigation of the Crystal Structure,Characterization, Hirshfeld Surface,and Theoretical Study of (C6H14N)5[HP2Mo5O23]·4H2O

The synthesis of an organoammonium diphosphopentamolybdates(VI), (C₆H₁₄N)₅[HP₂Mo₅O₂₃] · 4H₂O ( 1 ), is reportet. The molecular structure and spectroscopic analysis were performed using experimental techniques like X‐ray diffraction, FT‐IR, and UV/Vis. The single crystal analysis of the title compound shows that the compound crystallizes in the monoclinic crystal system with space group P2₁/c and cell constants of a = 12.7934(2) Å, b = 14.8145(2) Å, c = 27.2637(5) Å, and β = 92.9298(14)°. The Hirshfeld surfaces and the associated 2D fingerprint plots were investigated to study the intermolecular interactions in the crystal packing and this study has confirmed that the hydrogen bonding interactions play a dominating role in the stability of crystal structure. The theoretical calculations were done using PM3 semi‐empirical model and several properties were studied.     

Metal–Organic Cyclohelicates as Optical Receptors for Glutathione: Syntheses,Structures, and Host–Guest Behaviors

Two trinuclear zinc‐based cyclohelicates, Zn–PDB (PDB=[5‐(dibenzylamino)‐N1′,N3′‐bis(pyridin‐2‐ylmethylene)isophthalohydrazide]) and Zn–PMB (PMB=[5‐(bodipy‐oxy)‐N1′,N3′‐bis(pyridin‐2‐ylmethylene)isophthalohydrazide]) containing dibenzylamino and BODIPY groups, respectively, were generated by incorporating two amide‐containing tridentate chelators into meta‐positions of a substituted phenyl ring. Single‐crystal structure analysis and related spectroscopic characterizations demonstrated the formation of macrocyclic helicals both in the solid state and in solution. The host–guest behavior of the cyclohelical hosts towards γ‐glutamyl‐cysteinyl‐glycine (GSH) and its component amino acids was investigated by spectroscopic titrations. UV/Vis absorption titration and NMR titrations of Zn–PDB and Zn–PMB upon addition of the above‐mentioned guests suggested that the Glu residue of GSH was positioned within the cavity. The COO⁻ groups interacted with metal ions through static interactions. The Cys moiety of GSH interacted with the amide groups sited in host molecules through hydrogen‐bonding interactions to produce measurable spectral changes. Fluorescent titrations of Zn–PMB upon the addition of GSH and ESI‐MS investigations of the titration solutions confirmed the host–guest interaction modes and revealed the possible 1:1 complexation stoichiometry. These results showed that the recognition of a substrate within the cavity of functionalized metal–organic cage‐like receptors could be a useful method to produce supramolecular sensors for biomolecules.     

(π)C—H···S, (allyl)C—H···C(π) and π···π intermolecular interactions: synthesis, characterization, and crystal structure of 2,2′-bipyridine bis(diallyldithiocarbamato)zinc(II)

A mixed-ligand Zn(II) complex formulated as [Zn(aldtc)₂(bipy)] (aldtc=diallyldithiocarbamate; bipy=2,2′-bipyridine) was synthesized and characterized by IR, ¹H and ¹³C NMR spectral measurements and X-ray crystallography. The crystal structure of this complex indicates that Zn has a distorted octahedral geometry. The Zn—N distances are invariant (2.168(2) Å), while those of the Zn—S are slightly different (2.5408(9) and 2.5440(9) Å). The N—Zn—N, S—Zn—S and N—Zn—S bond angles are in the range 75.35(13)–99.75(7)°, 70.48(3)–161.02(5)° and 95.26(7)–160.32(7)°, respectively. The crystal packing of the complex shows different motifs of supramolecularity resulting from both hydrophilic ((π)C—H···S) and hydrophobic ((allyl)C—H···C(π)) intermolecular interactions. These interactions result in a chain arrangement of molecules along crystallographic c axis and the chains are further connected via π···π stacking along with ((π)C—H···S along b axis leading to an overall crystal packing that can be regarded as layers of complexes along bc plane, which are held together through nonconventional hydrogen bonding and π···π stacking.     

Single‐armed salamo‐like dioxime and its multinuclear Cu (II), Zn (II) and Cd (II) complexes: Syntheses,structural characterizations,Hirshfeld analyses and fluorescence properties

Three multinuclear Cu (II), Zn (II) and Cd (II) complexes, [Cu₂(L)(μ‐OAc)]·CHCl₂ ( 1 ), [Zn₂(L)(μ‐OAc)(H₂O)]·3CHCl₃ ( 2 ) and [{Cd₂(L)(OAc)(CH₃CH₂OH)}₂]·2CH₃CH₂OH ( 3 ) with a single‐armed salamo‐like dioxime ligand H₃L have been synthesized, and characterized by FT‐IR, UV–vis, X‐ray crystallography and Hirshfeld surfaces analyses. The ligand H₃L has a linear structure and C‐H···π interactions between the two molecules. The complex 1 is a dinuclear Cu (II) complex, Cu1 and Cu2 are all five‐coordinate possessing distorted square pyramidal geometries. The complex 2 also forms a dinuclear Zn (II) structure, and Zn1 and Zn2 are all five‐coordinate bearing distorted trigonal bipyramidal geometries. The complex 3 is a symmetrical tetranuclear Cd (II) complex, and Cd1 is a hexa‐coordinate having octahedral configuration and Cd2 is hepta‐coordinate with a pentagonal bipyramidal geometry, and it has π···π interactions inside the molecule. In addition, fluorescence properties of the ligand and its complexes 1 – 3 have also been discussed.     

Cobalt(II) Complex with a Tridentate N Donor Ligand: Synthesis,Crystal Structure,Antioxidation, and DNA Binding Studies

A heptacoordinated mononuclear cobalt(II) complex of tridentate bis(N‐ethylbenzimidazol‐2‐ylmethyl)aniline (Etbba) formulated as [Co(Etbba)(pic)₂] · (MeCN) (pic = picrate), was synthesized and characterized by elemental analysis, electric conductivity measurements, as well as IR and UV/Vis spectroscopy. The crystal structure of the cobalt(II) complex was determined by single‐crystal X‐ray diffraction. The study shows the metal atom in a distorted monocapped octahedral arrangement that comprises two picrate molecules and one Etbba ligand molecule. The DNA‐binding properties of the cobalt(II) complex were investigated by electronic absorption and fluorescence spectroscopy, as well as viscosity measurements. The experimental results suggest that the cobalt(II) complex binds to DNA in an intercalating mode. In addition, the complex shows strong scavenging effects for hydroxyl radicals.     

Polymeric and monomeric dipicolinate complexes with 4-hydroxymethyl pyridine: spectral, structural, thermal and electrochemical characterization

Polymeric copper(II), [Cu(μ-dpc)(μ-4-hymp)] _n (1), and monomeric nickel(II), [Ni(dpc)(4-hymp)(H₂O)₂]·H₂O (2), (dpc: dipicolinate, 4-hymp: 4-hydroxymethyl pyridine), dipicolinate complexes have been prepared and characterized by spectroscopic (IR, UV–Vis, EPR), thermal (TG/DTA), X-ray diffraction technique and electrochemical methods. In both the dipicolinate complexes, the dpc dianion acts as a tridentate ligand. In polymeric copper(II) complex, the 4-hymp and dpc ligands adopt a bridging position between the Cu(II) centers, forming the elongated octahedral geometry. The polymeric chains are linked to one another via O–H···O hydrogen bond interactions, forming the 3-D polymeric structure. The Ni(II) ion is bonded to dpc ligand through pyridine N atom together with one O atom of each carboxylate group, two aqua ligands and N pyridine atom of 4-hymp, forming the distorted octahedral geometry. The Ni(II) complexes are connected to one another via O–H···O hydrogen bonds, forming R ₄²(18) motifs in 2-D pattern. The powder EPR spectra of copper(II) complex have indicated that the paramagnetic center is in rhombic symmetry with the Cu²⁺ ion having distorted octahedral geometry. IR and UV–Vis spectroscopes all agree with the observed crystal structure.     

Synthesis,Crystal Structure and Spectroscopic Properties of [2,13‐Bis(1‐naphthalenylmethyl)‐5,16‐dimethyl‐2,6,13,17‐tetraazatricyclo(14,4,01.18,07.12)docosane]copper(II) Diperchlorate Acetonitrile Disolvate

The N‐functionalized macrocyclic ligand 2,13‐bis(1‐naphthalenylmethyl)‐5,16‐dimethyl‐2,6,13,17‐tetraazatricyclo(14,4,0^1.18,0^7.12)docosane (L³) and its copper(II) complex were prepared. The crystal structure of [Cu(L³)](ClO₄)₂·2CH₃CN was determined by single‐crystal X‐ray diffraction at 150 K. The copper atom, which lies on an inversion centre, has a square planar arrangement and the complex adopts a stable trans‐III configuration. The longer distance [2.081(2) Å] for Cu–N(tertiary) compared to 2.030(3) Å for Cu–N(secondary) may be due to the steric effect of the attached naphthalenylmethyl group on the tertiary nitrogen atom. Two perchlorate ions are weakly attached to copper in axial sites and are further connected to the ligand of the cation through NH ··· O hydrogen bonds [N ··· O 3.098 Å]. IR and UV/Vis spectroscopic properties are also described.     

Synthesis,Crystal Structure,Antioxidation and DNA‐Binding Studies of a Zinc(II) Complex with the Bis(N‐allylbenzimidazol‐2‐ylmethyl)aniline

A complex of zinc(II) picrate (pic) with bis(N‐allylbenzimidazol‐2‐ylmethyl)aniline (abba), with composition [Zn(abba)₂](pic)₂, was synthesized and characterized by elemental analysis, electrical conductivity, IR and UV/Vis spectral measurements. The crystal structure of the zinc(II) complex has been determined by single‐crystal X‐ray diffraction. The Zn(II) is bonded to two abba ligands through four benzimidazole nitrogen, resulting in a distorted tetrahedron geometry. The DNA‐binding properties of the ligand and the zinc(II) complex were investigated by electronic absorption, fluorescence spectra and viscosity measurements. The experimental results suggest that the zinc(II) complex binds to DNA in an intercalation mode. In addition, the ligand abba and Zn(II) complex have scavenging effects for hydroxyl radicals and the complex shows stronger scavenging effects for hydroxyl radicals than the ligand.     

Synthesis and structure of a Schiff base and its bivalent transition metal complexes

A Schiff base (HCSmz) was synthesized via (E)-cinnamaldehyde with S-methyl dithiocarbazate and six bivalent transition metal complexes [M(CSmz)₂] (M=Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺) were prepared. The complexes were characterized by elemental analyses, IR, ¹H NMR, and UV-Vis spectra, and the Ni(II) and Zn(II) complexes were also characterized by single crystal X-ray diffraction. After tautomerism of thiotone to thioenol and deprotonization of the thioenol, two ligands chelate the metal by two nitrogens of azomethine and two sulfurs of thioenol. Ni(CSmz)₂ crystallizes in the centrosymmetric space group P2₁ /n with a perfectly square planar trans-configuration with Ni located at the center of the square; crystal packing is stabilized by intra- and intermolecular C–H···S hydrogen bonds. Zn(CSmz)₂ is in the mirror-symmetric space group I4₁ /a in a distorted tetrahedral geometry with two equivalent Zn–N and Zn–S bonds; crystal packing is stabilized by intermolecular C–H···π hydrogen bonds.     

Synthesis,characterization, spectroscopic and theoretical studies of transition metal complexes of new nano Schiff base derived from l‐histidine and 2‐acetylferrocene and evaluation of biological and anticancer activities

A new Schiff base derived from the condensation of 2‐acetylferrocene with l ‐histidine was prepared and characterized using elemental analyses and spectroscopic methods. Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of the Schiff base were prepared and characterized using various physicochemical methods such as elemental analysis, Fourier transform infrared and UV–visible spectroscopies, molar conductance, thermal analysis and scanning electron microscopy (SEM). Both ligand and complexes were investigated for their biological and anticancer activities. The elemental analyses showed that complexes were formed in a metal‐to‐ligand ratio of 1:1 stoichiometry. The spectral analyses proved that the ligand was tridentate and all complexes had an octahedral geometry, except the Zn(II) complex that was tetrahedral. SEM showed that the ligand and its Cd(II) complex were of nanometric structure. The molecular and electronic structure of the free ligand was optimized theoretically and the quantum chemical parameters were calculated. The molecular structure can be used to investigate the coordination sites and the total charge density around each atom. According to anticancer studies, Cd(II) complex was recommended to be used as anti‐breast cancer drug as it had very low IC₅₀ (3.5 μg ml^?1). Molecular docking was used to predict the binding between the free ligand and its Cd(II) complex and crystal structure of Staphylococcus aureus (PDB ID: 3Q8u), receptors of breast cancer mutant oxidoreductase (PDB ID: 3Hb5) and crystal structure of Escherichia coli (PDB ID: 3 T88) and to identify the binding mode and the crucial functional groups interacting with the three proteins.     

cis-bis(Saccharinato)cobalt(II) and -zinc(II) complexes with 2-dimethylaminoethanol: syntheses,crystal structures,spectroscopic and thermal studies

2-Dimethylaminoethanol (dmea) reacted with tetraaqua-bis(saccharinato)cobalt(II) and -zinc(II) in n-butanol to yield the new complexes cis-[Co(sac)₂(dmea)₂] (1), and cis-[Zn(sac)₂(dmea)₂] (2) (sac?=?saccharinate). The complexes were characterized by elemental analyses, IR spectroscopy, DTA-TG and X-ray crystallography. Both complexes are isomorphous and crystallize in the monoclinic space group P2₁/c. The cobalt(II) and zinc(II) ions are coordinated by two neutral dmea ligands and two sac anions in a distorted octahedral environment. The dmea ligand acts as a bidentate N, O donor through the amine N and hydroxyl O atoms, while the sac ligand exhibits non-equivalent coordination, behaving as an ambidentate ligand; one coordinates to the metal via the carbonyl oxygen atom, while the other is N-bonded. The packing of the molecules in the crystals of both complexes is achieved by aromatic π(sac)–π(sac) stacking interactions, C–H?·?π interactions and weak intermolecular C–H?·?O hydrogen bonds involving the methyl groups of dmea and the sulfonyl oxygen atoms of the sac ligands. IR and UV spectra and thermal analysis are in agreement with the crystal structures.     

Synthesis and characterization of a zinc(II) complex of 1,3-bis(1-benzylbenzimidazol-2-yl)-2-oxopropane

A ligand 1,3-bis(1-benzylbenzimidazol-2-yl)-2-oxopropane (Bobb) and the zinc(II) complex, [Zn(Bobb)₂](picrate)₂ · 2DMF, were synthesized and characterized by elemental analyses, electrical conductivities, IR, and UV. The crystal structures of the ligand and the zinc complex have been determined by single crystal X-ray diffraction. The ligand displays a V-shaped configuration and the Zn(II) cation is six-coordinate by four nitrogens and two oxygens from Bobb. The N₄O₂ donor set is a distorted octahedron.     

Copper(II) Complex of a Urea-functionalized Pyridyl Ligand: Synthesis,Crystal Structure,and Acetate Binding Properties

A copper(II) acetate complex with a urea-functionalized pyridyl ligand, [CuL(OAc)₂]₂ · 2AcOH ( 1 ) [L = N-(3-chlorophenyl)-N'-(3-pyridyl) urea], was synthesized by the reaction of L with Cu(OAc)₂ in methanol. A zigzag-shaped hydrogen bond chain of L is obtained via urea N–H ··· N_pyridyl interactions, and a two-dimensional hydrogen bond network structure is further formed through the C–H ··· O interaction. In the complex 1 , a paddle-wheel structure is generated by Cu ··· O_acetate interactions and Cu ··· N_pyridyl interactions. Furthermore, hydrogen bonding chain structure is extended through weak C–H ··· O hydrogen bond interactions. Through ultraviolet-visible (UV/Vis) spectroscopy, the acetate binding properties of L in solution were also evaluated. Variable temperature magnetic susceptibility measurement indicates that the metal complex 1 displays antiferromagnetic coupling property.     

Synthesis,characterization, and biological screening of metal complexes of novel sulfonamide derivatives: Experimental and theoretical analysis of sulfonamide crystal

This study reports the synthesis of sulfonamide-derived Schiff bases as ligands L ¹ and L ² as well as their transition metal complexes [VO(IV), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II)]. The Schiff bases (4-{E-[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzene-1-sulfonamide ( L ¹ ) and 4-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}-N-(5-methyl-1,2-oxazol-3-yl)benzene-1-sulfonamide ( L ² ) were synthesized by the condensation reaction of 4-aminobenzene-1-sulfonamide and 4-amino-N-(3-methyl-2,3-dihydro-1,2-oxazol-5-yl)benzene-1-sulfonamide with 2-hydroxy-3-methoxybenzaldehyde in an equimolar ratio. Sulfonamide core ligands behaved as bidentate ligands and coordinated with transition metals via nitrogen of azomethine and the oxygen of the hydroxyl group. Ligand L ¹ was recovered in its crystalline form and was analyzed by single-crystal X-ray diffraction technique which held monoclinic crystal system with space group (P2₁/c). The structures of the ligands L ¹ and L ² and their transition metal complexes were established by their physical (melting point, color, yields, solubility, magnetic susceptibility, and conductance measurements), spectral (UV–visible [UV–Vis], Fourier transform infrared spectroscopy, ¹H NMR, ¹³C NMR, and mass analysis), and analytical (CHN analysis) techniques. Furthermore, computational analysis (vibrational bands, frontier molecular orbitals (FMOs), and natural bonding orbitals [NBOs]) were performed for ligands through density functional theory utilizing B3LYP/6-311+G(d,p) level and UV–Vis analysis was carried out by time-dependent density functional theory. Theoretical spectroscopic data were in line with the experimental spectroscopic data. NBO analysis confirmed the extraordinary stability of the ligands in their conjugative interactions. Global reactivity parameters computed from the FMO energies indicated the ligands were bioactive by nature. These procedures ensured the charge transfer phenomenon for the ligands and reasonable relevance was established with experimental results. The synthesized compounds were screened for antimicrobial activities against bacterial (Streptococcus aureus, Bacillus subtilis, Eshcheria coli, and Klebsiella pneomoniae) species and fungal (Aspergillus niger and Aspergillus flavous) strains. A further assay was designed for screening of their antioxidant activities (2,2-diphenyl-1-picrylhydrazine radical scavenging activity, total phenolic contents, and total iron reducing power) and enzyme inhibition properties (amylase, protease, acetylcholinesterase, and butyrylcholinesterase). The substantial results of these activities proved the ligands and their transition metal complexes to be bioactive in their nature.     

Nickel(II) complex with an asymmetric tetradentate Schiff base ligand: synthesis,characterization, crystal structure,and DFT studies

Abstract

A new asymmetric tetradentate Schiff base, bis(5-methoxysalicylidene)-4-methylbenzene-1,2-diamine), H₂L, and its Ni(II) complex were prepared and characterized using elemental analyses (CHN), FTIR, UV–Vis, ¹H NMR, and ¹³C{¹H} NMR spectroscopic techniques, and crystal structures of both were determined by X-ray crystallography. For both ligand and Ni(II) complex, density functional theory calculations to find geometry parameters, IR frequencies, electronic properties, and natural bond orbital analysis (NBO) were done with M062X method and Def2-TZVP basis set. All calculated data are consistent with the experiments. NBO data for the Ni(II) complex show that the main type of transition in UV-Vis is interligand charge-transfer, which is assigned as π-π*.