Bis[S-octyl 3-(2-methyl-propyl-idene)di-thio-carb-az-ato-κ2N3,S]nickel(II).

The central NiII atom in the title complex, [Ni(C13H25N2S2)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.

Interaction with CT-DNA and in vitro cytotoxicity of two new copper(II)-based potential drugs derived from octanoic hydrazide ligands.

Two copper(II) complexes [Cu(Hpmoh)(NO3)(NCS)] (1) and [Cu(peoh)(N3)]2 (2) were designed and synthesized by reaction of Cu(NO3)2·3H2O 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)(NO3)(NCS)] (1) and [Cu(Hpmoh)(NO3)(H2O/DMSO)] (1a) in one system and [Cu(peoh)(N3)] (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 104 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)(N3)] units.

A water-soluble Pd4 molecular tweezer for selective encapsulation of isomeric quinones and their recyclable extraction.

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 Pd4L2 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(NO3)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.

Pt(II) Tetrafacial Barrel with Aggregation-Induced Emission for Sensing.

A new tetraphenylpyrazine-based tetraimidazole ligand (L) was synthesized and used for subcomponent self-assembly with cis-(tmeda)Pd(NO3)2 and cis-Pt(PEt3)2(OTf)2, leading to the formation of two tetrafacial barrels [Pd8L4(tmeda)8](NO3)16 (1) and [Pt8L4(PEt3)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.

A novel nickel(II) complex with N,S donor Schiff base: Structural characterisation, DFT, TD-DFT study and catalytic investigation.

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.

Crystal structure of bis-{S-octyl-3-[(thio-phen-2-yl)methyl-idene]di-thio-carbazato-κ2N3,S}nickel(II).

In the title complex, [Ni(C14H21N2S3)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) Šalong the b-axis direction.

Crystallographic elucidation of an aluminium-bound amido Schiff base chemosensor: a selective turn-on fluorescent chemosensor for Al3+ ions.

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 I2/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 Al3+ ions in aqueous DMF media. Importantly, we have reported the first structurally characterized six-coordinate dinuclear Al3+ complex ([Na(Al2L2)·2H2O·4DMF], complex 1 (where ligand, L = sensor 1). Complex 1 crystallizes in the space group P1̄. X-ray single crystal diffraction studies for complex 1 reveal that each Al3+ 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 Na2EDTA 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 Al3+ ions under UV light.

Crystal structure of 4-[(4-methyl-benz-yl)-oxy]-N'-(4-nitro-benzyl-idene)benzohydrazide: a new hydrazone derivative.

The mol-ecular structure of the title compound, C22H19N3O4, 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.

Crystal structure of bis-[4-(all-yloxy)-N'-(but-2-en-1-yl-idene)benzohydrazidato]nickel(II).

In the title complex, [Ni(C14H15N2O2)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.

Crystal structures of 4-[(4-methyl-benz-yl)-oxy]benzohydrazide and its N'-[(thio-phen-2-yl)-methyl-idene]- derivative.

The mol-ecular and crystal structures of a benzoyl-hydrazine bearing an ether group, 4-[(4-methyl-benz-yl)-oxy]benzohydrazide, C15H16N2O2, (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, C20H18N2O2S, (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-NH2 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.

4-(All-yloxy)benzohydrazide.

The non-H atoms of the title compound, C10H12N2O2, 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.

Crystal structure of S-n-octyl 3-(1-phenyl-ethyl-idene)di-thio-carbazate and of its bis-chelated nickel(II) complex.

The nitro-gen-sulfur Schiff base proligand S-n-octyl 3-(1-phenyl-ethyl-idene)di-thio-carbazate, C17H26N2S2 (HL), was prepared by reaction of S-octyl di-thio-carbamate with aceto-phenone. Treatment of HL with nickel acetate yielded the complex bis-[S-n-octyl 3-(1-phenyl-ethyl-idene)di-thio-carbazato]nickel(II), [Ni(C17H25N2S2)2] (NiL 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 Ni2+ are described, involving a ca 180° rotation around the N(azomethine)-C(thiol-ate) bond.

Ionic Dioxidovanadium(V) Complexes with Schiff-Base Ligands as Potential Insulin-Mimetic Agents-Substituent Effect on Structure and Stability.

Four dioxidovanadium(V) complexes with Schiff-base ligands based on 2-hydroxybenzhydrazide with four different substituted salicylaldehydes (5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde, 5-nitrosalicylaldehyde, 3-bromo-5-chlorosalicylaldehyde) were synthesized and described, by using V2O5 and triethylamine. The single crystal X-ray structure measurements as well as elemental analyses and IR spectra confirmed the formulas of the ionic complexes with a protonated triethylamine acting as counterion, HTEA[VO2(L)] (HL = Schiff-base ligand). The kinetic stability of the complexes at pH = 2 and 7 was discussed with respect to the neutral vanadium(V) complexes previously studied as potential insulin-mimetic agents. A correlation between the substituents in an aromatic ring of the Schiff-base ligands with crystal packing, and also with the stability of the compounds, was presented.

Crystal structure of bis-{4-[(4-methyl-benz-yl)-oxy]-N'-(4-methyl-benzyl-idene)benzohydrazidato}nickel(II).

In the title complex, [Ni(C23H21N2O2)2], the central NiII atom is located on an inversion centre and exhibits a slightly distorted square-planar N2O2 coordination environment. A trans-configuration of the N,O chelating ligands results from the imposed site symmetry of the central NiII atom. In the crystal, individual mol-ecules stack along the a axis through weak π-π stacking inter-actions between the phenyl rings.

Crystal structure of ethyl 4-[(4-methyl-benz-yl)-oxy]benzoate.

The title compound, C17H18O3, crystallizes with three mol-ecules in the asymmetric unit. The mol-ecules differ in the conformation related to the eth-oxy group and in the orientation of the two phenyl rings, one of which has the eth-oxy group disordered over two positions with refined occupancies of 0.735:0.265 (9). In the crystal packing, the mol-ecules are connected by weak C-H⋯π inter-actions.

Interaction with bioligands and in vitro cytotoxicity of a new dinuclear dioxido vanadium(V) complex.

One centrosymmetric bis(µ-oxido)-bridged vanadium(V) dimer with molecular formula [(VVO2)2(pedf)2] (1) has been synthesized from the reaction of VOSO4·5H2O with a Schiff base ligand (abbreviated with pedf-) obtained from 2-acetylpyridine and 2-furoic hydrazide in methanol. Complex 1 was characterized by elemental analysis, UV-visible (UV-Vis), Fourier-transform infrared spectra (FT-IR), cyclic voltammetry (CV), electron paramagnetic resonance spectroscopy (EPR) and electrospray ionization-mass spectrometry (ESI-MS) techniques along with single crystal X-ray diffraction (SCXRD). The FT-IR spectral data of 1 indicated the involvement of oxygen and azomethine nitrogen in coordination to the central metal ion. The crystallographic studies revealed a dinuclear oxovanadium(V) complex with the Schiff base coordinated via the ONN donor set with formation of two five-membered chelate rings resulting in a distorted octahedral geometry. The interaction of 1 with calf thymus DNA (CT-DNA) was investigated by spectroscopic measurements and results suggested that the complex binds to CT-DNA via moderate intercalative mode with a binding constant (Kb) around 103 M-1. In addition, the in vitro protein binding behavior was studied by fluorescence spectrophotometric method using both bovine serum albumin (BSA) and human serum albumin (HSA) and a static quenching mechanism was observed for the interaction of the complex with both albumins that occurs with a Kb in the range (5-6) × 103 M-1. In vitro cytotoxicity of complex 1 on lung cancer cells (A549) and human skin carcinoma cell line (A431) demonstrated that the complex had a broad-spectrum of anti-proliferative activity with IC50 value of 64.2 µM and 56.2 µM.

Fluorescence enhancement via structural rigidification inside a self-assembled Pd4 molecular vessel.

Restriction of intramolecular motion (RIM) is fundamental for the high emission of aggregation-induced emission (AIE)-active molecules in aggregates or the solid-state. However, they are weakly emissive in dilute solution, which limits their application in dilute solutions. A Pd4 molecular vessel (MP1) was constructed by assembling [cis-(en)Pd(NO3)2] (M) with a tetradentate donor (L) in a 2 : 1 molar ratio. The active intramolecular motions of an AIE active molecule SG are restricted in the narrow cavity of MP1 upon encapsulation. As a result, SG displayed significant enhancement in its emission in dilute solution upon addition of MP1. This strategy of achieving high emission of AIE active compounds in dilute solution by confinement driven RIM might have potential in designing materials for high emission in the aggregated state as well as in dilute solution.

The tetrel bonding role in supramolecular aggregation of lead(II) acetate and a thiosemicarbazide derivative.

A new PbII coordination complex [PbL(OAc)], which was readily synthesized from a mixture of Pb(OAc)2·3H2O and 1-(pyridin-2-yl)benzylidene-4-phenylthiosemicarbazide (HL) is reported. The crystal structure analysis of [PbL(OAc)] showed that the PbII cation is N,N',S-chelated by the tridentate pincer-type ligand L and by the oxygen atoms of the acetate anion. In addition, the metal centre forms Pb...O and Pb...S tetrel bonds with an adjacent complex molecule, yielding a 1D zigzag polymeric chain, which is reinforced by N-H...O hydrogen bonds and π...π interactions. These chains are interlinked by C-H...py non-covalent interactions, realized between one of the acetate hydrogen atoms and the pyridine rings. According to the Hirshfeld surface analysis, the crystal packing is mainly characterized by intermolecular H...H, H...C and H...O contacts, followed by H...N, H...S, C...C, C...N, Pb...H, Pb...O and Pb...S contacts. The FTIR and 1H NMR spectra of [PbL(OAc)] testify to the deprotonation of the parent ligand HL, while the acetate ligand exhibits an anisobidentate coordination mode as established by means of single-crystal X-ray diffraction and FTIR spectroscopy. Lastly, theoretical calculations at the PBE0-D3/def2-TZVP level of theory have been used to analyze and characterize the Pb...O and Pb...S tetrel bonds observed in the crystal of [PbL(OAc)], using a combination of QTAIM (Quantum Theory of Atoms in Molecules) and NCIPlot (Non-Covalent Interaction Plot) computational tools.

Conformation-Selective Self-Assembly of Pd6 Trifacial Molecular Barrels Using a Tetrapyridyl Ligand.

A conformationally flexible tetrapyridyl ligand L was assembled separately with three cis-blocked 90° PdII acceptors (M1, M2, and M3) containing different blocking diamines. Surprisingly, different conformations of the donor L were arrested by the acceptors depending on the nature of the blocking amine, leading to the formation of isomeric Pd6 barrels (B1, B2, and B3). B2 and B3 with larger windows have been used to encapsulate polyaromatic hydrocarbons.

Correction: On the importance of π-hole spodium bonding in tricoordinated HgII complexes.

Correction for 'On the importance of π-hole spodium bonding in tricoordinated HgII complexes' by Ghodrat Mahmoudi et al., Dalton Trans., 2020, 49, 17547-17551, https://doi.org/10.1039/D0DT03938A.