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A nitrogen-sulfur Schiff base HL (1) derived from S-hexyldithiocarbazate and 4-methylbenzaldehyde has been reacted with different divalent metal ions in 2:1 molar ratio, producing neutral complexes (2–7) of general formula MIIL2 (where M = Ni, Cu, Zn, Cd, Pd and Pb). All compounds were characterized using established physico-chemical and spectroscopic methods. The single crystal structures of CuII and ZnII complexes are compared and discussed with those of NiII and PdII already reported by us, underlining the geometrical variations occurring in the HL ligand upon coordination. The metal complexes, as revealed by the X-ray diffraction analyses, show a square planar or tetrahedral coordination geometry, and in the former case either a cisoid or transoid configuration of chelating ligands. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations have been performed on the isolated cis/trans complexes of Ni and Pd complexes in order to evaluate the stability of the isomer isolated in solid state. The thermodynamic parameters for trans to cis isomerization of NiL2 complex [ΔH = −29.12 kJ/mol and ΔG = −43.97 kJ/mol] indicated that the trans isomer (observed in solid state) is more stable than the cis one. On the other hand, relative enthalpy [ΔH = −4.37 kJ/mol] and Gibbs free energy [ΔG = −5.50 kJ/mol] of PdL2 complex disclosed a small difference between the energies of the two isomers. Experimental UV–vis and TD-DFT calculation confirmed that these complexes have distinctive LMCT bands with a broad shoulder at 400–550 nm. With the purpose of providing insight into the properties and behavior of the complexes in solution, photoluminescence and electrochemical experiments have been also performed. Finally, the anti-bacterial activity of these compounds was evaluated against three pathogenic Gram-negative organisms such as Escherichia coli, Salmonella typhi and Shigella flexneri, but only the free ligand 1 showed anti-bacterial property against all three tested organisms.

The title compound, C14H20N2OS2 [systematic name: S-hexyl (E)-2-(2-hydroxybenzylidene)hydrazine-1-carbodithioate], crystallizes with four independent molecules (A–D) in the asymmetric unit. All four molecules adopt an E conformation with respect to the C=N bond of the benzylidene moiety and have an intramolecular O—H...N hydrogen bond generating an S(6) ring motif. In the crystal, the A and D molecules are connected by a pair N—H...S hydrogen bonds, forming a dimer with an R22(8) ring motif. In the case of molecules B and C, they are linked to themselves by pairs of N—H...S hydrogen bonds, forming B–B and C–C inversion dimers with R22(8) ring motifs.

The title compound, C32H30N4O2S4, consists of two Schiff base moieties, namely two S-benzyl-β-N-(2-hydroxyphenylethylidene)dithiocarbazate groups, which are connected through an S—S single bond. These two moieties are twisted with respect to each other, with a dihedral angle of 87.88 (4)° between the S2C=N planes. A bifurcated intramolecular O—H...(N,S) hydrogen bond is observed in each moiety. In the crystal, molecules are linked by pairs of C—H...O hydrogen bonds into inversion dimers. The dimers are further stacked in a column along the b axis through weak C—H...π interactions.

In the title complex, [Cu(C16H24N3S2)2], the CuII atom is coordinated by two azomethine N and two thiolate S atoms of the chelating Schiff base ligands, resulting in a distorted square-planar coordination environment. The S—Cu—N chelating angle is of 84.41 (5)°. The CuII atom is located on a crystallographic inversion centre, leading to a trans configuration of the N,S-chelating ligands.

In the title complex, [Pd(C12H17N2S3)2], the PdII atom exhibits a square-planar coordination geometry with the N,S-chelating ligands arranged in a trans configuration. Intramolecular C—H...S hydrogen bonds are observed. In the crystal, molecules are linked by weak C—H...N hydrogen-bond interactions, forming chains parallel to the b axis.

In the title complex, [Pd(C15H21N2OS2)2], the PdII ion is located on a crystallographic inversion center. The two Schiff base ligands in a deprotonated imino thiolate form chelate the metal atom via the azomithine N and thiolate S atoms in a trans-square-planar configuration as imposed by the crystal symmetry. The complex has an approximately planar geometry with the exception of the hexyl chains; the mean plane of the five-membered chelate ring makes a dihedral angle of 15.43 (5)° with the benzene ring. In the crystal, the complex molecules are stacked along the a axis.

The title compound, C18H20N2O3S2, a dithiocarbazate derivative, adopts an E conformation about the C=N bond. The trimethoxyphenyl group and the dithiocarbazate fragment lie almost in the same plane, with the mean plane of the dithiocarbazate unit being inclined to the trimethoxyphenyl ring by 13.34 (6)°. The aromatic rings are inclined to one another by 75.30 (9)°. In the crystal, molecules are linked via pairs of N—H...S hydrogen bonds, forming inversion dimers with an R22(8) ring motif. The dimers are linked via C—H...O hydrogen bonds, forming undulating sheets lying parallel to (103) which are linked via C—H...π interactions, forming a three-dimensional supramolecular structure.

The title compound, [Cu2(C14H18N2OS2)2], is a binuclear copper(II) complex of an oxybenzylidenedithiocarbazate ligand. The ligand coordinates in a tridentate manner through N-, S- and O-donor atoms. Each O atom also bridges to a second CuII ion to form the binuclear species. It has a central Cu2O2 rhomboid moiety and a metal-to-metal separation of 2.9923 (6) Å. In the crystal, the binuclear complexes stack along the a axis with all the hexyl chains located side-by-side, forming a hydrophobic region. The complexes are linked via C—H...N hydrogen bonds, forming chains along the c-axis direction. One CuII atom has the S atom of a symmetry-related complex located approximately in the apical position at 2.9740 (11) Å. This weak interaction links the chains to form slabs parallel to the ac plane.

As already observed in similar molecules, the dithiocarbazate group in the title compound, C17H26N2OS2, adopts an EE configuration with respect to the C=N bond of the benzylidene moiety. In the crystal, molecules are connected into inversion dimers by pairs of N—H...S hydrogen bonds. The dimers are linked by weak π–π interactions, with centroid-to-centroid distances of 3.723 (11) Å, forming chains parallel to [110].

In the title compound, C15H22N2OS2, the dithiocarbazate group adopts an EE conformation with respect to the C=N bond of the benzylidene moiety. The hexyl side chain adopts an extended conformation and the C—S—C—C torsion angle is −93.36 (13)°. In the crystal, inversion dimers linked by pairs of N—H...S hydrogen bonds generate R22(8) loops.

In the title complex, [Ni(C15H21N2S2)2], the NiII atom exhibits a square-planar coordination geometry and is located on an inversion centre leading to a trans configuration of the N,S-chelating ligands. In the crystal, the complex molecules stack at a distance of 4.6738 (3) Å along the a axis, which exclude any significant interactions between the aromatic rings.

In the title complex, [Cd(C17H15N2S2)2], the CdII ion is located on a twofold rotation axis and exhibits a coordination number of four within a very distorted coordination environment that is best described as bisphenoidal. The two deprotonated Schiff base ligands chelate the CdII ion through the azomethine N and the thiolate S atom. The dihedral angle between the two chelating ligands is 84.01 (9)°. Weak intermolecular C—H...S interactions lead to the formation of chains along the c axis.

In the title compound, [Hg(C17H15N2S2)2], the HgII ion lies on a crystallographic twofold rotation axis giving a very distorted tetrahedral coordination geometry best described as bisphenoidal, being chelated by two deprotonated N,S Schiff base ligands through the azomethine nitrogen and the thiolate sulfur donors. The dihedral angle between the two chelating ligand moieties is 79.75 (10)°. In the crystal, weak C—H...S interactions give rise to chains extending along the c axis.

In the title compound, C16H25N3OS, the thiosemicarbazone group adopts an E configuration with respect to the C=N bond and is almost coplanar with the benzene ring, forming a dihedral angle of 9.3 (1)°. In the crystal packing, the molecules lie along the a axis in an antiparallel arrangement and are held in place by van der Waals interactions. As a consequence, there is relatively low anisotropic thermal motion in the terminal atoms of the n-octyl chain.

The title molecule, C18H20N2O4, is located on a crystallographic centre of symmetry. The methoxy groups are coplanar with the benzene ring [interplanar angles of 14.4 (2) and 3.1 (3)°], indicating a conjugation effect.

This study investigates the non-covalent interactions between [Au(CN) 4 ] - anions and silver and zinc complexes, with a particular focus on coinage bonding interactions. Four new complexes, [Ag 2 (pyNP) 2 ][Au(CN) 4 ] 2 (1) [Zn(bipy) 3 ][Au(CN) 4 ] 2 (2), [Zn(phen) 3 ][Au(CN) 4 ] 2 (3) and [Zn(terpy)(H 2 O) 3 ][Au(CN) 4 ] 2 (4), were synthesized and spectroscopically characterized, including their X-ray solid-state structures, where pyNP is (2-(2-pyridyl)-1,8-naphthyridine, bipy is 2,2' bipyridine, phen is 1,10'-phenantroline and terpy is terpyridine. The [Au(CN) 4 ] - anion exhibits unique anion⋯anion interactions, despite the electrostatic repulsion, forming stable 1D supramolecular polymers in the solid state. Using a combination of X-ray crystallography and DFT calculations, this work characterizes the coordination and non-covalent bonding modes, including Au⋯N coinage bonds. Energy decomposition analysis (EDA), QTAIM, and NCIplot methods were applied to understand the energetics and bonding nature. The study reveals that electrostatic and dispersion forces play critical roles in stabilizing these assemblies, especially in the formation of π-stacking and T-shaped dimers. These findings offer insights into the design of new materials leveraging coinage bonding in molecular architectures.

Electrical performances of a biphenyl-derived amido Schiff base ligand L and its dinuclear Al(iii) complex (complex 1) were investigated in a metal-semiconductor (MS) junction. Electrical studies revealed that complex 1 significantly enhanced the electrical conductivity and improved the characteristics of a Schottky barrier diode (SBD). The I - V characteristics demonstrated that complexation of ligand L with Al(iii) ion increased the conductivity by two orders of magnitude (conductivity of L = 1.04 × 10 -7 Sm -1 and complex 1 = 1.04 × 10 -5 Sm -1 ) with improved diode rectification ratio. Complex 1 extended itself to the 3D supramolecular array by virtue of the hydrogen bond, C-H⋯π(C) bond and π⋯π interactions. This significantly influenced the semiconducting behaviour of complex 1 and essentially improved the characteristics of SBD. The optical band gap of complex 1 and ligand L in the solid state was determined experimentally (2.63 eV and 3.04 eV, respectively) and compared with the theoretical value obtained from DFT calculations. Furthermore, DOS analysis explained the conductivity behavior of complex 1 in a logically better way., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

The asymmetric unit of the title salt co-crystal, C 5 H 6 N + ·C 2 HO 4 - ·C 2 H 3 ClO 2 , comprises a pyridinium cation, a carb-oxy-formate anion and a 2-chloro-acetic acid mol-ecule. In the crystal, the components are connected by hydrogen bonds within a one-dimensional chain in the a -axis direction which incorporates rather short, charge-assisted O-H⋯O hydrogen bonds; the pyridinium-NH group forms bifurcated N-H⋯(O,O) hydrogen bonds of different strength., (© Sadikhova et al. 2025.)

Two copper(II) complexes [Cu(Hpmoh)(NO 3 )(NCS)] (1) and [Cu(peoh)(N 3 )] 2 (2) were designed and synthesized by reaction of Cu(NO 3 ) 2 ·3H 2 O with hydrazone Schiff base ligands,abbreviated with Hpmoh and Hpeoh. Hpmoh and Hpeoh were prepared by condensation reaction of octanoic hydrazide with pyridine-2-carboxyaldehyde and 2-acetylpyridine, respectively. Complexes 1 and 2 were characterized using different analytical techniques such as FT-IR, UV-Vis, IR, EPR and single X-ray diffraction (XRD) analyses as well as computational methods (DFT). The XRD of 1 and 2 shows a mononuclear or a dinuclear structure with the copper(II) centre adopting a slightly distorted square pyramidal geometry. In water-containing solution and in DMSO, 1 and 2 undergo a partial transformation with formation of [Cu(Hpmoh)(NO 3 )(NCS)] (1) and [Cu(Hpmoh)(NO 3 )(H 2 O/DMSO)] (1a) in one system and [Cu(peoh)(N 3 )] (2a) in the other one, as supported by DFT calculations. Docking simulations confirmed that the intercalation is the preferred binding mode with DNA for 1, 1a and 2a, but suggested that the minor groove binding is also possible. A significant fluorescence quenching of the DNA-ethidium bromide conjugate was observed upon the addition of complexes 1 and 2 with a quenching constant around 10 4  M -1  s -1 . Finally, both 1 and 2 were examined for anti-cancer activity using MDA-MB-231 (human breast adenocarcinoma) and A375 (malignant melanoma) cell lines through in vitro MTT assay which suggest comparable cancer cell killing efficacy, with the higher effectiveness of 2 due to the dissociation into two [Cu(peoh)(N 3 )] units., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The central Ni II atom in the title complex, [Ni(C 13 H 25 N 2 S 2 ) 2 ], is located on an inversion center and adopts a roughly square-planar coordination environment defined by two chelating N , S donor sets of two symmetry-related ligands in a trans configuration. The Ni-N and Ni-S bond lenghts are 1.9193 (14) and 2.1788 (5) Å, respectively, with a chelating N-Ni-S bond angle of 86.05 (4)°. These data are compared with those measured for similar di-thio-carbazato ligands that bear n -octyl or n -hexyl alkyl chains. Slight differences are observed with respect to the phenyl-ethyl-idene derivative where the ligands are bound cis relative to one another., (© Khan et al. 2024.)

Quinones (QN) are one of the main components of diesel exhaust particulates that have significant detrimental effects on human health. Their extraction and purification have been challenging tasks because these atmospheric particulates exist as complex matrices consisting of inorganic and organic compounds. In this report, we introduce a new water soluble Pd 4 L 2 molecular architecture (MT) with an unusual tweezer-shaped structure obtained by self-assembly of a newly designed phenothiazine-based tetra-imidazole donor (L) with the acceptor cis -[(tmeda)Pd(NO 3 ) 2 ] (M) [ tmeda = N , N , N ', N '-tetramethylethane-1,2-diamine]. The molecular tweezer encapsulates some quinones existing in diesel exhaust particulates (DEPs) leading to the formation of host-guest complexes in 1 : 1 molar ratio. Moreover, MT binds phenanthrenequinone (PQ) more strongly than its isomer anthraquinone (AQ), an aspect that enables extraction of PQ with a purity of 91% from an equimolar mixture of the two isomers. Therefore, MT represents an excellent example of supramolecular receptor capable of selective aqueous extraction of PQ from PQ/AQ with many cycles of reusability., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A new tetraphenylpyrazine-based tetraimidazole ligand ( L ) was synthesized and used for subcomponent self-assembly with cis -(tmeda)Pd(NO 3 ) 2 and cis -Pt(PEt 3 ) 2 (OTf) 2 , leading to the formation of two tetrafacial barrels [Pd 8 L 4 (tmeda) 8 ](NO 3 ) 16 ( 1 ) and [Pt 8 L 4 (PEt 3 ) 16 ](OTf) 16 ( 2 ), respectively. Although ligand L is aggregation-induced emission (AIE) active, barrel 2 showed a magnificently higher AIE activity than ligand L , while 1 failed to retain the AIE properties of the ligand. Pd(II) barrel 1 , undergoing an aggregation-caused quenching (ACQ) phenomenon, nullified the AIE activity of the ligand to be used in the photophysical application. The enhanced emission in the aggregated state of Pt(II) barrel 2 was used for the recognition of picric acid (PA), which is explosive in nature and one of the groundwater contaminants in landmine areas. The recognition of picric acid was found to be selective in comparison with that of other nitroaromatic compounds (NACs), which could be attributed to ground-state complex formation and resonance energy transfer between picric acid and barrel 2 . The use of new AIE-active assembly 2 for selective detection of PA with a low detection limit is noteworthy.

The nitro-gen-sulfur Schiff base proligand S - n -octyl 3-(1-phenyl-ethyl-idene)di-thio-carbazate, C 17 H 26 N 2 S 2 (H L ), was prepared by reaction of S -octyl di-thio-carbamate with aceto-phenone. Treatment of H L with nickel acetate yielded the complex bis-[ S - n -octyl 3-(1-phenyl-ethyl-idene)di-thio-carbazato]nickel(II), [Ni(C 17 H 25 N 2 S 2 ) 2 ] (Ni L 2 ), which was shown to adopt a tetra-hedrally distorted cis -square-planar coordination geometry, with the NiSN planes of the two ligands forming a dihedral angle of 21.66 (6)°. Changes in the geometry of the L ligand upon chelation of Ni 2+ are described, involving a ca 180° rotation around the N(azomethine)-C(thiol-ate) bond., (© Khan et al. 2023.)

One new mononuclear nickel(II) thiosemicarbazone complex (1), has been synthesised from the Schiff base ligand derived from p-anisaldehyde and thiosemicarbazide. Complex 1 is characterized by using different spectroscopic techniques and single crystal X-ray structure analysis. Time dependent density functional theory (TD-DFT) was performed to simulate the electronic spectra of the complex 1 with the help of Polarizable Continuum Model (PCM) model. Complex 1 acts as functional models. The catalytic property has been evaluated from Lineweaver-Burk plot using the Michaelis-Menten approach of enzyme catalysis with a kcat value of the order of 708 h-1.

We have synthesized a biphenyl-derived two arm-containing amido Schiff base, bis((2-hydroxynaphthalen-1-yl) methylene)-[1,1'-biphenyl]-2,2'-dicarbohydrazide (sensor 1), having hard donors to facilitate chelation with hard metal centers. The crystal structure of sensor 1 reveals that it crystallizes in the monoclinic system with the space group I 2/ a and shows several types of intra/inter-molecular H-bond interactions, which stabilized the crystal lattice. The sensing property of sensor 1 towards different metal ions has been demonstrated using different analytical techniques. In fact, sensor 1 shows high fluorescence selectivity and sensitivity towards Al 3+ ions in aqueous DMF media. Importantly, we have reported the first structurally characterized six-coordinate dinuclear Al 3+ complex ([Na(Al 2 L 2 )·2H 2 O·4DMF], complex 1 (where ligand, L = sensor 1). Complex 1 crystallizes in the space group P 1̄. X-ray single crystal diffraction studies for complex 1 reveal that each Al 3+ ion is hexa-coordinated by four oxygen and two nitrogen atoms from each arm of the two ligands. The sodium ion has penta-coordination in a highly distorted trigonal bipyramidal geometry, surrounded by two μ-bridging naphtholate oxygen atoms and three solvent DMF oxygen atoms. Upon addition of Na 2 EDTA to complex 1, no spectral change or naked-eye colour change was observed. Furthermore, "test kits" coated with sensor 1 showed successful selective detection of Al 3+ ions under UV light.

In the title complex, [Ni(C 14 H 21 N 2 S 3 ) 2 ], the nickel(II) atom is located on a crystallographic inversion center and exhibits a square-planar coordination environment, being coordinated by two negatively charged N,S - chelating ligands in a trans configuration. In the crystal, the non-H atoms of the complex are practically coplanar (r.m.s. deviation of fitted atoms = 0.135 Å), and the angle between the thienyl and the chelating rings is 6.7 (1)°. The mol-ecules stack at a distance of 3.623 (2) Å along the b -axis direction., (© Khan et al. 2023.)

The mol-ecular structure of the title compound, C 22 H 19 N 3 O 4 , shows a non-coplanar conformation, with dihedral angles between the phenyl rings of 73.3 (1) and 80.9 (1)°. These deformations are induced by the crystal packing that is mainly governed by N-H⋯O and C-H⋯O hydrogen bonds, forming a mono-periodic arrangement parallel to the b axis., (© Banna et al. 2023.)

In the title complex, [Ni(C 14 H 15 N 2 O 2 ) 2 ], the nickel(II) atom exhibits a square-planar coordination geometry, being coordinated by two negatively charged N , O chelating ligands in a trans configuration, with the metal located on a crystallographic center of symmetry. The X-ray structural characterization showed the complex to be disordered over two orientations with refined occupancies of 0.898 (2) and 0.102 (2). The whole mol-ecule is close to planar, the five- and six-membered rings subtending a dihedral angle of 7.5 (2)°. The crystal packing is supported by C-H⋯π and C-H⋯O inter-actions that form a di-periodic layered network., (© Khan et al. 2023.)

The mol-ecular and crystal structures of a benzoyl-hydrazine bearing an ether group, 4-[(4-methyl-benz-yl)-oxy]benzohydrazide, C 15 H 16 N 2 O 2 , (I), and of the corresponding N '-[(thio-phen-2-yl)-methyl-idene]- derivative, 4-[(4-methyl-benz-yl)-oxy]- N '-[(thio-phen-2-yl)-methyl-idene]benzohydrazide, C 20 H 18 N 2 O 2 S, (II), are described. The supra-molecular structures of both compounds are governed by N-H⋯N and N-H⋯O hydrogen-bonding inter-actions. The hydrazine compound (I) shows a crystal packing with a more complex hydrogen-bonding scheme because of the NH-NH 2 entity, forming a di-periodic supra-molecular structure extending parallel to (100). Hydrazone mol-ecules in (II) are hydrogen-bonded through N-H⋯O inter-actions, giving rise to the formation of ribbons parallel to [010]. Mol-ecules of (I) and (II) show a different orientation of the carbohydrazide moiety likely to favor the crystal packing and thus hydrogen-bonding inter-actions., (© Banna et al. 2023.)

The non-H atoms of the title compound, C 10 H 12 N 2 O 2 , are approximately coplanar with the exception of those at the ends: the terminal allyl carbon atom and terminal hydrazide nitro-gen atom are displaced from the mean plane by 0.67 (2) and 0.20 (2) Å, respectively. In the crystal, the mol-ecules are linked by N-H⋯O and N-H⋯N hydrogen bonds, which give rise a two-dimensional network propagating in the (001) plane., (© Khan et al. 2023.)