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Two novel complexes [Zn(L)2·(NO3)2] (1) and [Ni(L)2·2H2O]·2CH3OH·(NO3)2 (2) (L = 2‐(2‐thiazolyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide) were synthesized successfully and characterized by elemental analysis, as well as various spectroscopic techniques. Specifically, the photoluminescence behavior of complex 1 was explored in different solvents. The structural characterization of both complexes has been determined single‐crystal X‐ray diffraction. It revealed that the metals in 1 and 2 are chelated by two L ligands in centro‐symmetrically fashion and the complexes are counterbalanced by nitrate ions which act as coordinating species in 1, while two water molecules complete the Ni coordination sphere in 2. In the crystal structures, the adjacent molecules of complex 1 disclosed a ladder‐like 2‐D network and 3‐D supramolecular self‐assembly. Simultaneously, an infinite 1‐D chain, 2‐D layered skeleton, and even meter‐shaped 3‐D network of 2 was governed by molecular interactions (H–bonds, C–H⋯π). Most strikingly, the research of antibacterial activity proved that two complexes had good activity against two standard bacteria strains. To ascertain deeply the optimum geometric configurations and detect the frontier molecular orbital energy gaps, density functional theory (DFT) calculations were also investigated. Additionally, analyses of Hirshfeld surfaces (HS) and electrostatic potential (ESP) were also performed to quantify the presence of diverse noncovalent interactions. [ABSTRACT FROM AUTHOR]

Two mono‐ and dinuclear Bi(III) complexes, [Bi(L)2(NO3)2]·NO3 (1) and [Bi2(L)2Cl8] (2) (L = (2‐(2‐pyridyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide), were obtained via complexation of L with Bi(III) nitrate pentahydrate and Bi(III) chloride. L and both complexes were characterized by elemental analyses and spectroscopic methods including FT‐IR, UV–Vis, and fluorescence spectroscopy. Specifically, it clearly manifested that both complexes had good fluorescence emission and showed different fluorescence behaviors in diverse solvents. Both Bi(III) complexes were further determined by X‐ray crystallography, and it was found that the ratio of ligand to metal was 2:1 in 1, whereas 2 was 1:1. Their coordination geometric configurations were significantly different, such as octa‐coordinated complex 1 formed an infinite 1‐D chain‐like, funnel‐shaped 2‐D network, and ladder‐like 3‐D supramolecular framework, whereas hexa‐coordinated complex 2 with a binuclear structure exhibited two slightly distorted octahedral geometric structures; meanwhile, symmetric units came into being an infinite 2‐D layer even and meter‐shaped 3‐D supramolecular skeleton. The optimal geometries, frontier molecular orbital energies, and molecular electrostatic potential diagrams of both complexes were calculated using DFT/B3LYP. The electronic distribution of HOMO‐LUMO rationalized the results of UV–Vis spectra with the help of TD‐DFT calculations. Furthermore, all samples demonstrated excellent antibacterial activities against Escherichia coli and Staphylococcus aureus. In addition, non‐covalent interactions of complexes and their contributions were quantified with Hirshfeld surfaces using CrystalExplorer17 program. [ABSTRACT FROM AUTHOR]

The quinazoline‐type ligand 2‐(3‐ethoxy‐2‐hydroxyphenyl)‐4‐methyl‐1,2‐dihydroquinazolin 3‐oxide (HL1, H is the deprotonatable hydrogen) was synthesized. Two mono‐ and dinuclear Cu (II) complexes, [Cu(L2)2]·2CH3OH (1), and [Cu4(L2)4(NO3)2] (2) (HL2 = 1‐(2‐{[(E)‐(3‐ethoxy‐2‐hydroxybenzylidene]amino}phenyl)ethanone oxime), were obtained via complexation of HL1 with Cu (II) acetate monohydrate or Cu (II) nitrate trihydrate in methanol. HL1 and both complexes were characterized by elemental analyses and spectroscopic methods. The structures of complexes were confirmed by single‐crystal X‐ray crystallography and the ratio of ligand to metal in 1 was 2:1 whereas 2 was 1:1. In the crystal structures, hexa‐coordinated Cu (II) complex 1 was assembled into an infinite 1‐D, 2‐D network and 3‐D supramolecular framework. Complex 2 included four deprotonated (L2)− units, four coordinated Cu (II) and two coordinated nitrate anions, forming an infinite 2‐D layer and interesting butterfly‐shaped 3‐D supramolecular skeleton. Specifically, the Cu1 and Cu4 centers were four‐coordinated, while the Cu2 and Cu3 centers were penta‐coordinated in 2. Furthermore, electrochemical properties and antibacterial activities of both complexes were also investigated. In addition, the electron paramagnetic resonance (EPR) spectra of 1 and 2 were also studied. The optimal geometries, HOMO‐LUMO energies and molecular electrostatic potential diagrams of two complexes were calculated using density functional theory (DFT)/B3LYP, and specific electronic transitions in the UV–vis spectra of 1 and 2 were recorded by time‐dependent DFT (TD‐DFT) calculations. Additionally, the noncovalent interactions between both complexes were also confirmed by Hirshfeld surfaces. [ABSTRACT FROM AUTHOR]

Two complexes [Cd(L)2(NO3)2] (1) and [Ni(L)2(OH)2][Ni(L)2(CH3OH)2](NO3)2·CH3OH (2) (L = 2‐[2‐pyridyl]‐4‐methyl‐1,2‐dihydroquinazolin 3‐oxide) were gained via complexation an amount of the new ligand L with different nitrate salts. The obtained complexes were characterized by elemental analysis, spectroscopy, and X‐ray crystallographic. In the crystal structure, centrosymmetric 1 adopted slightly distorted octahedral geometry. On the other hand, the independent unit of 2 contained two half Ni (II) complex located on a center of symmetry, differing for the axial ligand, two uncoordinated nitrate ions, and one lattice methanol molecule. Both the crystal structures formed a 3‐D supramolecular architecture through different interactions (H‐bonds, π···π, etc). X‐ray crystallography revealed that complexes 1 and 2 had 2:1 ligand‐to‐metal ratios. Most strikingly, 1 performed different fluorescence behaviors in diverse solvents, whereas 2 exhibited fluorescence quenching. When 1 was dissolution in N,N‐dimethylformamide (DMF) solvent system, it has better fluorescence properties. The geometry optimization and HOMOs and LUMOs energies of both complexes were calculated by density functional theory (DFT) methods, and the nucleophilic and electrophilic attack sites were confirmed with electrostatic potential (ESP) calculations. Preliminary investigation of antimicrobial activities of all compounds against Gram‐negative bacteria (Escherichia coli) and Gram‐positive bacteria (Bacillus subtilis) was reported. Additionally, CrystalExplorer program was used to quantify the noncovalent interactions in complexes 1 and 2 through Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

Two complexes [Co(L)2·2CH3OH]2·(NO3)4 (1) and [Cd(L)2(NO3)2] (2) (L = 2‐(2‐imidazolyl)‐4‐methyl‐1,2‐dihydroquinazoline‐3‐oxide) were synthesized by natural evaporation of Co (II)/Cd (II) nitrate with a new heterocyclic ligand. The metal complexes are characterized by elemental analysis, spectroscopy, and X‐ray crystallographic. In the crystal structures, Co (II) complex 1 was in a six‐coordinated coordination environment and constituted an infinite 1‐D chain, 2‐D network, Meter‐shaped 3‐D supramolecular framework, while Cd (II) complex 2 assembled into an infinite 1‐D, wave‐like 2‐D, and dragonfly‐shaped 3‐D skeleton. Specifically, nitrate ions were present as a dissociated group in complex 1, whereas complex 2 was involved in the coordination. Moreover, Cd (II) complex exhibited different fluorescence behaviors in diverse solvents. Remarkably, all the compounds have shown perceptible antibacterial activity against Gram‐positive and Gram‐negative bacteria. Furthermore, the electrostatic potential (ESP) calculations were utilized to analyze electrophilic and nucleophilic attack sites on the molecule, which verified the existence of hydrogen bonds in the optimized crystal structure. In addition, the structural features of metal complexes have been remarkably rationalized, and the overall trends obtained in the experimental values have been resoundingly remade by TD/DFT calculations. The detailed Hirshfeld surface analysis and fingerprint plots yielded a comparative picture of the mode of non‐covalent interactions. [ABSTRACT FROM AUTHOR]

• Two 1-D, 2-D and 3-D supramolecular Cu(II) and Ni(II) complexes based on the quinazoline-type ligand L containing pyrazole ring were structural characterized. • The activity data showed the metal complexes to be more antibacterial than the quinazoline-type ligand L. • The experimental investigations match with those obtained from TD-DFT calculations. • ESP calculation results confirmed the charge distribution in the molecule and Hirshfeld surface analyses of both complexes were also discussed. The ligand 2-(3-pyrazolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide (L) was synthesized, and two transition metal complexes, namely [Cu(L) 2 ]·(NO 3) 2 (1) and [Ni(L) 3 ]·(NO 3) 2 ·3CH 3 OH (2) were prepared through complexation reaction between L and the corresponding metal salt. L and both complexes were characterized by elemental analysis, as well as compared with spectrographic technique for example FT-IR and UV–Vis spectroscopy. X-ray single-crystal diffraction demonstrated that 1 was tetra-coordinated square planar whereas 2 was hexa-coordinated slightly distorted octahedral geometry. Meanwhile, the metal-ligand ratios were 2:1 in 1 whereas 3:1 in 2. Through the superposition of hydrogen bonds and other weak interactions, both complexes formed 1-D chain-like, 2-D layered, and 3-D supramolecular structures. Theoretical investigations explained the optimized geometries of complexes and the electrostatic potential distribution in molecules, and also analyzed the electron transition types of L and both complexes in combination with UV–vis spectroscopy, which provided theoretical support for the experimental conclusions. Electrostatic potential (ESP) was computed for both complexes to predict the reaction positions of electrophilic and nucleophilic assaults. Hirshfeld Surface Analysis quantified interactions in molecules and analyzed the contribution of various weak interactions to stabilize the structure of complexes. Especially, antibacterial experiments displayed compounds had certain antibacterial activities against both Gram-positive and Gram-negative bacterial strains. The ligand 2-(3-pyrazolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide (L) was synthesized, and two metal complexes, namely [Cu(L) 2 ]·(NO 3) 2 (1) and [Ni(L) 3 ]·(NO 3) 2 ·3CH 3 OH (2) were prepared through complexation reaction between L and the corresponding metal salt. Both complexes were characterized by X-ray crystallography, spectroscopic methods such as FT-IR and UV–Vis spectroscopy, and electrochemical property, as well as Hirshfeld surface analysis and DFT studies. The antimicrobial activities of all compounds were also compared. [Display omitted] [ABSTRACT FROM AUTHOR]

• Two 2-D and 3-D supramolecular Ni(II) and Co(III) complexes based on 3-ethoxy salicylaldehyde were structural characterized. • X-ray crystallography revealed that the valence of cobalt ion is trivalent, EPR and cyclic voltammetry experiment also proved the result. • The experimental investigations match with those obtained from TD-DFT calculations. • ESP calculation results confirmed the charge distribution in the molecule and Hirshfeld surface analyses of complexes 1 and 2 were also discussed. The ligand 2-(3-ethoxy-2-hydroxyphenyl)-4-methyl-1,2-dihydroquinazolin 3-oxide (HL1 , H is the deprotonatable hydrogen) has been synthesized, and two metal complexes, namely [Ni(L2) 2 ]·2CH 3 OH (1) and [Co(L2) 2 ]·NO 3 ·H 2 O (2) (where HL2 =1-(2-{[(E)-(3- ethoxy -2- hydroxybenzylidene ]amino} phenyl)ethanone oxime) were obtained via complexation reaction between HL1 and nickel(II) acetate tetrahydrate or cobalt(II) nitrate hexahydrate. HL1 and both complexes were characterized by elemental analysis, as well as compared by spectroscopic methods such as FT-IR, UV–Vis and fluorescence spectroscopy. X-ray crystallography revealed that both complexes have distorted octahedral geometries but with a different configuration of the two tridentate (L2)– ligands around the metal centers. Complex 1 contained two lattice methanol molecules whereas 2 were counterbalanced by a nitrate anion beside an uncoordinated water molecule. The crystal structures show a 2-D and 3-D supramolecular architecture due to intermolecular interaction. Electrochemical properties of both complexes were tested by cyclic voltammetry and Electron paramagnetic resonance (EPR) spectroscopy of 2 was also investigated. Fascinatingly, antibacterial efficiencies of all compounds were compared. Furthermore, molecular electrostatic potential (ESP) was computed for both complexes to predict the reaction sites of electrophilic and nucleophilic attacks. Density Functional Theory (DFT) calculations were done to ascertain the optimum geometric configurations. The non-covalent interaction was determined using the Hirshfeld program. The quinazoline-type ligand HL1 , used for the synthesis of two discrete metal complexes, [Ni(L2) 2 ]·2CH 3 OH (1) and [Co(L2) 2 ]·NO 3 ·H 2 O (2), was observed to be modified upon complexation with HL2. Both complexes were characterized by X-ray crystallography, spectroscopic methods such as FT-IR, UV–Vis and fluorescence spectroscopy, and electrochemical properties, as well as Hirshfeld surface analysis and DFT studies. The antimicrobial activities of all compounds were also compared. [Display omitted] [ABSTRACT FROM AUTHOR]

Two new cobalt(II) complexes, [Co(L3)2]·CH3OH·CH3COCH3(1) (HL3= 1-(2-{[(E)-3,5-dichloro-2-hydroxybenzylidene]amino}phenyl)ethanone oxime) and Co(L4)2(2) (HL4= 1-(2-{[(E)-3,5-dibromo-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), have been synthesized via complexation of Co(II) acetate tetrahydrate withHL1andHL2.HL1,HL2,and their corresponding Co(II) complexes were characterized by IR,1H NMR spectra, as well as by elemental analysis and UV–Vis spectroscopy, respectively. The crystal structures of the complexes have been determined by single-crystal X-ray diffraction.1and2display that extensive hydrogen bonds and C–X···πbonding interactions construct the 1-D infinite chain [Co(L3)2]·CH3OH·CH3COCH3and Co(L4)2into 2-D supramolecular frameworks. The electrochemical properties of two Co(II) complexes were also investigated by cyclic voltammetry. Two new cobalt(II) complexes have been synthesized via complexation of Co(II) acetate tetrahydrate withHL1andHL2originally.HL1,HL2and their corresponding Co(II) complexes were characterized by IR,1H NMR spectra, as well as by elemental analysis and UV–Vis spectroscopy, respectively. The crystal structures of the complexes have been determined by single-crystal X-ray diffraction.1and2display that extensive hydrogen bonds and C-X···π bonding interactions construct the 1-D infinite chain [Co(L3)2]·CH3OH·CH3COCH3and Co(L4)2into 2-D supramolecular frameworks. The electrochemical properties of two Co(II) complexes were also investigated by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

Highlights: [•] An unexpected mononuclear Co(III) complex has been synthesized and structural characterized. [•] Single crystal X-ray analysis reveals that the valence of cobalt ion is trivalent. [•] Cyclic voltammetry and XPS experiment also proved that cobalt ion is trivalent. [ABSTRACT FROM AUTHOR]

• Both L and trinuclear Cd(II) complex were characterized by X-ray crystallography. • The experimental investigations match with those obtained from TD-DFT calculations. • ESP calculation results confirmed the charge distribution in the molecule and experimental investigations match with those obtained from TD-DFT calculations. • Hirshfeld surface analyses of L and trinuclear Cd(II) complex were also measured and discussed. Two three-dimensional supramolecular structures of L and [Cd 3 L 2 (CH 3 OH) 4 Cl 6 ] complex (L = 2-(6-bromopyridin-2-yl)-4-methyl-1,2-dihydroquinazoline- N 3-oxide), were synthesized and characterized by X-ray crystallography and elemental analysis, as well as FT-IR, UV–Vis, and fluorescence spectroscopy. The photoluminescence behavior of the Cd(II) complex was also investigated in different solvents. X-ray diffraction analysis results revealed that the Cd(II) complex was a trinuclear hexa-coordinate structure and made up of two L , three Cd2+ metal central, four methanol and six chlorine ions. In the crystal structures, it was noteworthy that L formed an infinite 1-D chain-like, 2-D square structure, parallelogram 3-D supramolecular skeleton, whereas the Cd(II) complex formed an infinite 1-D chain-like, 2-D ladder-like configuration, and even expanding into 3-D grid-like supramolecular frameworks. Density functional theory (DFT) calculation was used to compute the optimization, molecular frontier orbital energies (HOMO and LUMO). Specifically, owing to the combination of metal orbitals and the ligand, the energy gap of the complex was less than L. Electrostatic potential (ESP) was used to analyze the reaction sites of two compounds. On the basis of optimized geometry, time-dependent DFT (TD-DFT) simulated the electronic transitions rationalized the UV–Vis spectra peaks of L and Cd(II) complex. In addition, some non-covalent interactions were quantified by Hirshfeld surface and analyzed by Interaction region indicator (IRI). The new quinazoline-type ligand L and trinuclear Cd(II) complex, namely [Cd 3 L 2 (CH 3 OH) 4 Cl 6 ] were synthesized and structural characterized. Both L and the Cd(II) complex were characterized by X-ray crystallography and elemental analysis, as well as FT-IR, UV–Vis and fluorescence spectroscopy. Hirshfeld surface analysis and DFT studies were also discussed. Additionally, Electrostatic potential (ESP) was used to analyze the reaction sites of both compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

• Packing dimension of supramolecular complexes with N -heterocycle ligand were characterized by X-ray crystallography. • The antibacterial activities demonstrated that the metal complexes were the best among all the compounds and 2 was superior to 1. • The experimental investigation was matched with those obtained from TD-DFT calculations. • ESP calculation results manifested the charge distribution and Hirshfeld surface analyses were also further enhanced. Two 1-D, 2-D, 3-D supramolecular complexes, namely [Ni(L1) 2 (CH 3 OH) 2 ](NO 3) 2 (1) and [Cd(L2) 2 (NO 3) 2 ] (2) with N -heterocycle ligands (L1 = 2-(4-imidazolyl)-4-methyl-1,2-dihydroquinazoline-N3-oxide, L2 = 2-(2-thiazolyl)-4-methyl-1,2-dihydroquinazoline- N 3-oxide), were synthesized by corresponding nitrate and characterized by elemental analysis and spectroscopic methods. X-ray diffraction displayed that both complexes were hexa-coordination geometries and had 2:1 ligand-to-metal ratios. Ni(II) in 1 was coordinated with two L1 and two lattice methanol molecules, counterbalanced by nitrate ions, whereas Cd(II) in 2 by two L2 and nitrate ions. In the crystal structures, 1 based on an infinite 1-D chains to form 2-D wavy-like and 3-D supramolecular self-assembly. Similarly, 2 further developed 2-D and 3-D network structure by several interactions. The electrochemical behavior of 1 in DMF revealed the electronic effects on redox potential of the groups. Most conspicuously, the investigation of antibacterial activities demonstrated that both complexes had good activity against two selected bacteria strains. Density functional theory (DFT) by B3LYP method was used to obtain optimizations, frontier molecular orbital energies and electrostatic potential (ESP) of both complexes. On the basis of optimized geometries, time-dependent DFT (TD-DFT) recorded the specific electronic transitions in the UV-Vis spectra. In addition, the non-covalent interactions in 1 and 2 were analyzed by Hirshfeld surface analysis (HSA). [ABSTRACT FROM AUTHOR]