Bidentate Fashion Research Articles

Synthesis, Characterisation, and Coordination Behaviour of Novel Pyridyl‐formamidine Based Mn(I), Cu(II), Zn(II), and Pd(II) Complexes

AbstractWe report a new synthetic approach for the synthesis of less‐explored unsymmetrical pyridyl‐formamidine ligands and their coordination behaviour to form Mn(I), Cu(II), Zn(II), and Pd(II) complexes. The one‐step process for synthesising the unsymmetrical pyridyl‐formamidine compounds offers the advantage of being functional‐group tolerant and less cumbersome. Generally, the pyridyl‐formamidine ligands coordinate to the metal centres in a bidentate fashion to form a six‐membered chelate as established by spectroscopic and crystallographic analysis. It was observed that the formamidine functionality is prone to hydrolysis in the presence of methoxy substituent on the phenyl ring and/or acetate‐containing metal precursors.

The influence of the pyridyl substituent in N-methyl-P,P-diphenyl-N-2-pyridinyl-phosphinous amide ligand on the coordination chemistry of group 6B metal carbonyl derivatives

The reaction of N-methyl-P,P-diphenyl-N-2-pyridinyl-phosphinous amide (1) with group 6B metal hexa, tetra, and tricarbonyls yielded the same octahedral complexes cis-M(CO)4[1-κ2P,Npy] (M = Cr(2), Mo(3), W(4)) in which the ligand chelates only in a bidentate fashion through its phosphorus atom and pyridyl N-atom. Compounds 1–4 were identified and characterized by multinuclear NMR spectroscopy (1H, 13C, 31P NMR), elemental analysis, IR and UV–Vis spectroscopy. Complexes 2–4 exhibited weak metal-to-ligand charge transfer transitions unaffected by solvent polarity. Crystal structure determination is carried out on complex 4.

Photocatalytic dye degradation and hydrogen peroxide sensing by a novel copper-Schiff base complex prepared via mechanochemical method

ABSTRACT Water pollution, primarily caused due to hazardous organic and inorganic substances, is a cause of concern for human health and development, for it manifests adverse repercussions across health, economic, and social dimensions. The footprints of its adverse effects are also left on aquatic/marine life forms. In the light of the negative impacts of such substances, the development of efficient remediation techniques becomes pertinent. In this article, we report a water-soluble glutamic acid Schiff base copper complex (Cu-GSb) that has been synthesised by taking recourse to a mechanochemical approach, relying upon solid-state reagent interactions in a benign environmental setting, eluding a rigorous refluxing condition and overuse of solvents. The experimental results revealed that the ligand coordinates to the metal centre in a bidentate fashion through the imine nitrogen and carboxylate oxygen, respectively, adopting a distorted square planar geometry. Further, the complex’s utility in mitigating chemical hazards has been demonstrated through the studies involving degradation of organic dyes like methylene blue and bromocresol green, and decomposition/sensing of H2O2. Notably, as a photocatalyst towards the degradation of above-mentioned dyes under visible light irradiation, our study showed the photocatalytic efficiency of Cu-GSb to be ~95% in 50–60 min. The rate of degradation reaction has been found to follow first-order kinetics with rate constant values of 6 × 10−2 and 5.66 × 10−2 min−1 for MB and BCG, respectively. Furthermore, the results of H2O2 sensing evaluation revealed that the complex is capable of potentially decomposing H2O2 in about 20–30 min. The compounds have been routinely characterised by UV–visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and proton nuclear magnetic resonance (1H NMR).

Preparation, spectroscopic and anticancer investigations of metal-drug complexes associated between flumequine antibiotic drug with lanthanum(III), samarium(III) and terbium(III) chloride

Flumequine ligand (FLQ) metal complexes of the [M(FLQ)2(Cl)(H2O)].nH2O type, where M are (La(III), Sm(III), and Tb(III)) and FLQ is flumequine have been synthesized. The FLQ metal complexes could be prepared using MCl3 : flumequine in stoichiometry of 1:2 in situ bidentate chelation. The characterization of FLQ complexes obtained have been done using elemental analyses (%C, %H and %N), molar conductivity (Ʌm), infrared spectroscopy (FTIR), electronic spectra (UV-Vis), thermal analysis (TGA), and physicochemical techniques such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) measurements at room temperature. Accordingly, these complexes are indicative of an octahedral coordination structure. Flumequine ligand has a bidentate fashion through the oxygen atoms of carbonyl (quinolone) and carboxylic groups. The findings demonstrated the anti-cancer efficacy of these compounds against HepG-2 and MCF-7 cancer cell lines at extremely low doses of up to 58.2 mg/mL. The La(III) complex was shown to have the highest selectivity against cancer cells in comparable with both samarium and terbium(III) complexes.
 KEY WORDS: Flumequine, Lanthanide metal ions, FTIR, EDX, Complexation, Anticancer activity
 Bull. Chem. Soc. Ethiop. 2024, 38(3), 671-684. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i3.10

N′-(Furan-2-ylmethylene)-2-hydroxybenzohydrazide and its metal complexes: synthesis, spectroscopic investigations, DFT calculations and cytotoxicity profiling

The ligand, N′-(furan-2-ylmethylene)-2-hydroxybenzohydrazide (H2L), was synthesized characterized through various spectral studies which cleared out that the free ligand existed in keto form. The ligand upon reaction with Cu(II), Co(II), Ni(II) and Zn(II) acetates yielded complexes with stoichiometric ratio 1:2 (M:L) which has been validated through the elemental and mass spectral measurements. The IR and NMR spectral studies of the isolated complexes disclosed that the ligand chelated to metal ion in mononegative bidentate fashion via the azomethine nitrogen and deprotonated enolized carbonyl oxygen. Moreover, the DFT quantum chemical calculations designated that the ligand and Ni(II) complex exhibited the highest and lowest values of HOMO, LUMO energies and HOMO-LUMO energy gap, respectively. Furthermore, the in vitro cytotoxic activity towards HePG-2 and HCT-116 cell lines of the isolated compounds was investigated and the data cleared out that the ligand was more potent than the metal complexes.

Ligand redistribution hinders preparation of a nickel(II)-hydroxo

The synthesis is demonstrated for a heteroleptic Ni(II) complex, with a tridentate ligand bearing N-heterocyclic carbene (NHC), aryloxide, and picolyl donor groups. The compound was reacted with a variety of hydroxide sources, several of which resulted in complex mixtures. Reaction with [NH4]OH affords a bis-ligated nickel compound, in which the ligands are each bound in a bidentate fashion through the NHC and aryloxide donor groups. A desired nickel(II)-hydroxo product was not observed. DFT studies suggest that ligand redistribution is thermodynamically preferred over stabilization of a Ni-hydroxo in either a monomeric or dimeric form.

Transition metal complexes of N'-(2-cyanoacetyl)nicotinohydrazide: Synthesis, structural and anticancer activity studies

On reacting the nicotinic hydrazide with 1-cyanoacetyl-3,5-dimethylpyrazole, a new ligand, N'-(2-cyanoacetyl)nicotinohydrazide (H2L), was produced and characterized using diverse spectral studies which cleared out that the free ligand existed in keto form. The ligand reacted with Cu(II), Co(II), Ni(II) and Zn(II) acetates affording metal complexes with 1:1 (M:L) stoichiometric which was validated using the elemental and mass spectral measurements. The spectral studies of the isolated complexes showed that the ligand chelated to metal ion in mononegative bidentate fashion via the amide nitrogen and deprotonated enolized carbonyl oxygen group. Moreover, the DFT quantum chemical calculations indicated that the ligand has the highest HOMO-LUMO energy gap, ΔEH-L, while the Co(II) complex has the lowest and may be sorted as H2L > Zn(II) > Cu(II) > Ni(II) > Co(II). Furthermore, isolated compounds’ in vitro cytotoxic activity against HePG-2 and HCT-116 cell lines was investigated and the data cleared that the ligand has very strong, IC50 6.59 ± 0.4 and 8.17 ± 0.7 μM, respectively. Whereas, the metal complexes exhibited moderate to weak potent effect against both cell lines.

Structural and Photoluminescent Properties of a Novel Terbium Bis(thiocyanato)aurate, Tb[Au(SCN)2]3·6H2O

The reaction of Tb3+ ions with KAu(SCN)2 results in the formation of the crystalline coordination compound Tb[Au(SCN)2]3·6H2O. Single-crystal X-ray diffraction has been employed to investigate the structural features of this compound. The crystallographic data are as follows (Mo Kα, λ = 0.71073 Å): orthorhombic, Cmcm, a = 12.4907(9) Å, b = 8.5845(6) Å, c = 20.7498(8) Å, V = 3679.72(16) Å3, Z = 4, R1(I > 2(σ)) = 0.0232. This material represents the first known example of a lanthanide dithiocyanatoaurate compound. Au(SCN)2− anions bridge Tb3+ centers in a bidentate fashion to form the [Tb(H2O)4(Au(SCN)2)2]͚+ 1D chains present in the structure. Trimeric Au units in the structure contain short aurophilic bonding interactions with distances of 3.1066(4) Å. The more common O–H‧‧‧O and O–H‧‧‧N H-bonding interactions in the structure are overshadowed by relatively rare O–H‧‧‧S interactions involving the bis(thiocyanato)gold(I) anions. Photoluminescence measurements illustrate that Tb[Au(SCN)2]3·6H2O displays strong Tb3+-based emission, but there is a lack of Au-based emission down to 85 K. Excitation spectra are recorded for the title compound and these measurements demonstrate the presence of a donor–acceptor process within the compound, leading to enhanced Tb3+-based emission.

Racemic cis-bis-[bis-(pyrimidin-2-yl)amine-κN]bis(dicyanamido-κN1)iron(II) dihydrate: synthesis, crystal structure and Hirshfeld surface analysis.

The title compound, [Fe(C2N3)2(C8H7N5)2]·2H2O, has been synthesized solvothermally and characterized by single-crystal X-ray diffraction. The octa-hedral iron coordination polyhedron contains two di(pyrimidin-2-yl)amine ligands coordinated in a bidentate fashion, and two monodentate dicyanimido ligands, each coordinated via a terminal N atom, with the latter in a cis orientation. The ligand configuration about the iron atom is chiral, although the compound crystallizes as a racemic mixture: the Fe-N distances (> 2.07 Å) are characteristic of high-spin iron(II). In the crystal, an extensive series of N-H⋯N, O-H⋯N and O-H⋯O hydrogen bonds links the independent mol-ecular components into a three-dimensional framework. The H atoms of both water mol-ecules are disordered. The structure also features some π-π and anion-π inter-actions. The inter-molecular inter-actions were investigated by Hirshfeld surface analysis and two-dimensional fingerprint plots. Comparisons are made with some related compounds.

In vitro biological activities of novel Ni(II)-2-chloroquinoline derivative complex: Synthesis, characterization and computational studies

Quinoline derivative nickel complexes have received considerable attention in biomedical research. Herein, novel nickel(II) complex [Ni(II)(HL)2].2H2O was synthesized from newly synthesised ligand 2-((2-hydroxyethyl)amino)quinoline-3-carbaldehyde (H2L) through bidentate fashion of metal–ligand interaction. The complex was characterized using spectroscopic and physicochemical methods. The formation constant (KNi(II) = 2.36 × 107) of the complex was calculated spectroscopically and thermodynamic parameters (ΔG, ΔH and ΔS) were determined from it. In vitro antibacterial activity analysis of the newly synthesized complex exhibited mean inhibition zones ranging from medium to high (16.55 ± 1.03 mm, 16.69 ± 0.63 and 20.94 ± 2.01 mm) at 600 μg/mL against E. coli, S. aureus and P. aeruginosa, respectively. The complex also showed enhanced antioxidant activities compared with the corresponding free ligand. The energy band gap (1.183 eV) was calculated from the HOMO and LUMO of the most stable structure of the synthesized complex. The DFT calculated results and molecular docking analysis results showed good agreement with the experimental results. The complex showed pronounced biological activities than the free ligand. The in silico binding modes of the complex against E. Coli DNA Gyrase and S. aureus Dihydrofolate reductase (PDB: 2w9h) were found to be in excellent agreement with the in vitro biological studies.

Synthesis, crystal structure and Hirshfeld surface analysis of a copper(II) complex involving 3-methyl-benzoate and 2,2'-bi-pyridine ligands.

3-Methyl-benzoic acid (3-mbH) and 2,2'-bi-pyridine (bipy) reacted with a cop-per(II) salt forming a new mixed ligand complex, aqua-(2,2'-bi-pyridine-κ2 N,N')bis-(3-methyl-benzoato)-κ2 O,O';κO-copper(II) 0.68-hydrate, [Cu(C8H7O2)2(C10H8N2)(H2O)]·0.68H2O or [Cu(3-mb)2(bipy)(H2O)]·0.68H2O. The coord-ination environment of CuII is a distorted octa-hedron. The metal atom is attached to two 3-mb moieties, which bind in monodentate and bidentate fashions. One of the 3-mb units is disordered. The coordination environment is completed by one bipy ligand and a water mol-ecule. A second water mol-ecule is outside the coordination sphere of the CuII atom and its occupancy refined to 0.68. The structure consists of chains along the b-axis direction formed by complex units joined via hydrogen bonds between the coordinated water mol-ecule and an O atom of a coordinated 3-mb unit. Hirshfeld surface analysis indicates that the most abundant contacts are H⋯H (56.8%), H⋯C/C⋯H (21.7%) and H⋯O/O⋯H (13.7%).

Synthesis, characterization, spectroscopic study and biological evaluation of Zn(II), Ni(II), and Cu(II)complexes derived from(1-methyl-1H-imidazol-2-yl)methanol

This study focuses on the synthesis, the structural studies of four new divalent metal coordination complexes of (1-methyl-1H-imidazol-2-yl)methanol (Hmim), and the assessment of their antimicrobial activity against five pathogenic microorganisms as well as their antioxidant potential. M(II) complexes were prepared by condensation of Hmim with Zn(OAc)2, Cu(OAc)2, NiCl2·6H2O, or CuCl2 in dry 1,2-dimethoxyethane at rt.. The ligand and its complexes have been characterized systematically by elemental analysis, FT-IR and UV–vis spectroscopy, and single-crystal X-ray diffraction. In [Zn(Hmim)2(OAc)2] (1)four donor atoms surround the metal ion displaying tetra-coordinated compound in distorted tetrahedral geometry, while in [Cu(Hmim)3OAc].AcOH (2), the Cu(II) ion is coordinated by three Hmim ligands and one acetate ligand displaying a tetragonally distorted octahedral environment. In [Ni(Hmim)2(H2O)2]Cl2(3), and [Cu(Hmim)3]Cl2 (4), the ligand is coordinated to M(II) ions in bidentate fashion exhibiting a distorted octahedral environment, the chloride anions act only as counter ions. The free ligand and its complexes 1–4 were tested in vitro for their antimicrobial activity against the growth of five strains including Gram (+) and Gram (-) bacteria, a Gram (+) phytopathogenic bacteria, a yeast and a fungus using the agar diffusion method. The SAR study of the antibacterial activity revealed significant differences in their inhibition activity profile, where 1 gave the best results displaying significant inhibition effects with a broad spectrum. The free-radical scavenging activity of synthesized compounds was investigated through their DPPH radical scavenging capacity, and has shown moderate to interesting antioxidant potential.

Efficient Hydroboration of Esters and Nitriles Using a Quinazolinone‐Supported Titanium(IV) Multitasking Catalyst

AbstractWe report catalytic hydroboration of esters as well as nitriles under solvent‐free and mild conditions using single titanium(IV) metal complex, [{κ2‐C6H4C(O)N(iPr)C(N‐iPr)=N}{κ3‐(iPr)N=C(O)−C6H4−NC(NMe2)N(iPr)}TiNMe2] 1 as a sustainable, economical, and efficient pre‐catalyst. The molecular structure of the TiIV complex in the solid state reveals the unique coordination of TiIV metal with N, N, and O atoms of one quinazolinone unit via in‐situ rearrangement, while another quinazolinone moiety coordinates in bidentate fashion via both N atoms only. The TiIV complex demonstrates excellent activity as a pre‐catalyst towards the hydroboration of a wide array of esters and nitriles with pinacolborane (HBpin) to afford alkoxyboranes and diboryl amines in high yield (up to 99 %) with greater tolerance to a variety of electron‐withdrawing and electron‐donating functional groups. A most plausible mechanism of hydroboration of esters is also proposed based on kinetics and NMR studies, which suggests the formation of titanium‐hydride species as an active catalyst.

A combined spectroscopic and theoretical study to investigate the coordination modes of 2,3- and 3,4-pyridine dicarboxylates with Eu(III)

The complex formation of Eu(III) with 2,3-pyridine dicarboxylic acid (23PDCA) and 3,4-pyridine dicarboxylic acid (34PDCA) has been studied by luminescence spectroscopy in aqueous medium. About three orders of luminescence enhancement of Eu(III) was observed in Eu(III)-PDCA complexes compared to its aqua complex, Eu(H2O)93+. Stability constant values (Log KMLi) were obtained for various metal–ligand (MLi (i = 1–3)) complexes formed in the aqueous medium. Complexation studies along with luminescence lifetime data suggested that both the ligands bind with Eu(III) in a bidentate fashion. Interestingly, the bi-dentate mode of 23PDCA interaction with Eu(III) is dominantly through nitrogen atom of pyridyl and the oxygen atom of nearby carboxylate group, whereas in case of 34PDCA, the bi-dentate coordination is through the two oxygen atoms of both the carboxylate groups. The density functional theory (DFT) calculations provided insights into the complex formation at the molecular level and the theoretical results show excellent agreement with the experimental observations.

New Ligand-Based Metal Complexes: Synthesis, Spectroscopic Characterization, Thermal Behavior, Anticancer Properties, and Biological Activity

New ligands, N1, N4-bis (benzo[d]thiazol-2- ylcarbamothioyl) succinamide (L1) and N1, N4- bis (benzylcarbamothioyl)succinamide (L2), derived from succinyl chloride and 2-amino benzothiazole or benzylamine, respectively, have been used to prepare a set of transition metal complexes with the general formula [M2(L)Cl4], where L=L1 or L2, M = Mn(II), Ni(II), Cu(II), Cd(II), Co(II), Zn(II) or Hg(II). The synthesized compounds were characterized using various analytical techniques including TGA, 13C NMR, mass spectroscopy, 1H and Fourier-transform infrared (FTIR) spectroscopy, magnetic measurement, molar conductivity, electronic spectrum, (%M, %C, %H, %N) and atomic absorption flame (AAF) analysis. The results showed that (L1, L2) bind to the metal ion in a bidentate fashion through the (C=O) and (C=S) groups, and the complexes have a tetrahedral geometry. The antibacterial activity of the compounds was tested against two types of bacteria, Escherichia coli (−) and Staphylococcus aureus (+). Additionally, the anticancer activity of the Cu(II) and Co(II) complexes was evaluated by carrying out cell viability and cytotoxicity assays on the MCF-7 breast cancer cell line and comparing the results with those obtained for normal cells.

Hexacoordinated MIV (M=Ti, Zr, Hf) Tetrachlorido Complexes with Chelating Dithienylethane Based 1,2 Diketone Ligand – π‐Conjugation as Decisive Factor for Axial Chirality Mode

Abstract1,2‐bis(2,5‐dimethylthiophen‐3‐yl)ethane‐1,2‐dione (1, DTEthane) reacts with MCl4 metal precursors of group four (M=Ti, Zr, Hf) via coordination of the carbonyl groups. The molecular structure of complex 2–4 were determined in scXRD studies in the solid state and characterized by means of multi‐nuclear and multi‐dimensional NMR spectroscopy in solution. While the resulting titanium complex [TiCl4(DTEthane)] 2 shows a monomeric structure, where 1 binds in a bidentate fashion, complexes with a Zr (3) and Hf (4) center have dimeric scaffolds in which the ligands adopt a bridging mode. Quantum chemical calculations using density functional theory (G16, B97D3/def2‐TZVP) were used to evaluate the general trend of dimer formation (Ti<Zr<Hf). The molecular structures derived from both scXRD and the DFT optimized structures reveal the carbonyl groups in conjugation with the adjacent thiophene substituent. As a result, they are coplanar and rotation about the two C−C axes (C1−C7; C8−C9) is restricted allowing for only one chiral axis along C7−C8. This gains special importance with respect to previously described complexes carrying the closely related 1,2‐endiolato ligand (1,2‐bis(2,5‐dimethylthiophen‐3‐yl)ethene‐1,2‐diolate), in which no coplanarity of the thiophene rings to their neighboring metallacycle was observed allowing for two chiral axes. Noteworthy, further DFT calculations addressing the pathway of racemization found transition states, which are characterized by contrary rotations of both thiophene rings and a loss of conjugation rather than a direct rotation around the axis C7−C8.

Quantum-based modeling implies that bidentate Arg89-substrate binding enhances serine/threonine protein phosphatase-2A(PPP2R5D/PPP2R1A/PPP2CA)-mediated dephosphorylation.

PP2A-serine/threonine protein phosphatases function as heterotrimeric holoenzymes, composed of a common scaffold (A-subunit encoded by PPP2R1A/PPP2R1B), a common catalytic (C-subunit encoded by PPP2CA/PPP2CB), and one of many variable regulatory (B) subunits. The site of phosphoprotein phosphatase (PPP) hydrolysis features a bimetal system (M1/M2), an associated bridge hydroxide [W1(OH-)], and a highly-conserved core sequence. In the presumptive common mechanism, the phosphoprotein's seryl/threonyl phosphate coordinates the M1/M2 system, W1(OH-) attacks the central P atom, rupturing the antipodal bond, and simultaneously, a histidine/aspartate tandem protonates the exiting seryl/threonyl alkoxide. Based on studies of PPP5C, a conserved arginine proximal to M1 is also expected to bind the substrate's phosphate group in a bidentate fashion. However, in PP2A isozymes, the role of the arginine (Arg89) in hydrolysis is not clear because two independent structures for PP2A(PPP2R5C) and PP2A(PPP2R5D) show that Arg89 engages in a weak salt bridge at the B:C interface. These observations raise the question of whether hydrolysis proceeds with or without direct involvement of Arg89. The interaction of Arg89 with B:Glu198 in PP2A(PPP2R5D) is significant because the pathogenic E198K variant of B56δ is associated with irregular protein phosphorylation levels and consequent developmental disorders (Jordan's Syndrome; OMIM #616355). In this study, we perform quantum-based hybrid [ONIOM(UB3LYP/6-31G(d):UPM7)] calculations on 39-residue models of the PP2A(PPP2R5D)/pSer (phosphoserine) system to estimate activation barriers for hydrolysis in the presence of bidentate Arg89-substrate binding and when Arg89 is otherwise engaged in the salt-bridge interaction. Our solvation-corrected results yield ΔH‡ ≈ ΔE‡ = +15.5kcal/mol for the former case, versus +18.8kcal/mol for the latter, indicating that bidentate Arg89-substrate binding is critical for optimal catalytic function of the enzyme. We speculate that PP2A(PPP2R5D) activity is suppressed by B:Glu198 sequestration of C:Arg89 under native conditions, whereas the PP2A(PPP2R5D)-holoenzyme containing the E198K variant has a positively-charged lysine in this position that alters normal function.

Synthesis, spectral characterization and biological investigation of new organoruthenium(II) complexes with N, X-donor (X = S, O) heterocyclic chelators

New Ru(II) arene complexes containing 2,4-dihydroxyacetophenone based Schiff bases have been synthesized and characterized with FTIR, UV–visible, 1H NMR, 13C NMR and mass spectroscopies. Spectroscopic analysis revealed that the ligands coordinated to ruthenium(II) in a monobasic bidentate fashion via azomethine nitrogen and thiolate/oxalate. Antimicrobial activities of the compounds were evaluated with two bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) and two fungi (Candida albicans and Candida tropicalis). The complexes displayed better antimicrobial activity over their ligands. In addition, the ligands and the complexes were analyzed for their anticancer potential against A549 (human lung carcinoma) and HeLa (human cervical cancer) cells, in which the complexes exhibited comparable activities against A549 (IC50 value is 21 ± 1 µM (1), 18 ± 1 µM (2)) and HeLa (IC50 value is 22.1 ± 0.9 µM (1), 20 ± 1 µM (2)) with the standard drug cisplatin (IC50 value is 25 ± 1 µM (A549) and 27 ± 1 µM (HeLa)). The non-toxic nature of the compounds has been confirmed with human umbilical vein endothelial cells (HUVEC cells). The obtained results highlighted the possibility of developing ruthenium arene complexes as anticancer agents.

Closing the Shell: Gas-Phase Solvation of Halides by 1,3-Butadiene.

Gas-phase solvation of halides by 1,3-butadiene has been studied via a combination of photoelectron spectroscopy and density functional theory. Photoelectron spectra for X- ⋯(C4 H6 )n (X=Cl, Br, I where n=1-3, 1-3 and 1-7 respectively) are presented. For all complexes, the calculated structures indicate that butadiene is bound in a bidentate fashion through hydrogen-bonding, with the chloride complex showing the greatest degree of stabilisation of the internal C-C rotation of cis-butadiene. In both Cl- and Br- complexes, the first solvation shell is shown to be at least from the vertical detachment energies (VDEs), however for I- , increases in the VDE may suggest a metastable, partially filled, first solvation shell for and a complete shell at . These results have implications for gas-phase clustering in atmospheric and extraterrestrial environments.

New palladium (II) complexes from halogen substituted Schiff base ligands: Synthesis, spectroscopic, biological activity, density functional theory, and molecular docking investigations

Two novel palladium (II) complexes Pd(L1)2 and Pd(L2)2 derived from ON donor bidentate ligands: 2-(((2-bromo-4-chlorophenyl)imino)methyl)phenol (HL1) and 2-(((-bromo-4-methylphenyl)imino)methyl)phenol (HL2) are reported. The structures of the complexes are unequivocally established using 1H NMR, 13C{H}NMR, Fourier transform-infrared, UV–Vis, TGA, elemental analysis (CHN), mass spectrometry (HRMS), and single crystal X-ray diffraction (SCXRD). The SCXRD revealed that the complexes crystallized as a monoclinic system in P2(1)/c space group, in which two ligands coordinated to one Pd(II) center via oxygen and nitrogen atoms of phenolate and imine in a bidentate fashion, resulting in a square planar geometry. The ligands and their complexes were tested for anticancer activity against breast cancer (MCF-7) and colon cancer (HT-29) cell lines, as well as their toxicity profile on HepG-2, a liver cell line, using MTT assays, and compared to 5-fluorouracil (the control). Pd(L1)2 was found to be more active and selective than Pd(L2)2, and it reduced the cancerous cells' viability by more than 70%. Pd(L2)2 reduced the viability of MCF-7 and HT-29 cell lines by more than 50%. However, the ligands were unable to reduce cancerous cell viability by more than 40%. Both complexes had no effect on the HepG-2 liver cell line at lower concentrations. The two complexes had higher antioxidant activity against DPPH radicals, with IC50 values of 33.16 and 38.40 μgmL−1, respectively, than the ligands, which had IC50 values of 50.76 and 60.90 μgmL−1. Hirshfeld surface (HS) analysis was used to investigate the non-covalent interaction (NCI) of the complexes and their ligands. The tendency of a pair of chemical species to form crystal packing interactions is computed, which provides the complexes with good contacts in the crystal packing. The DFT studies were performed for the ligands and their complexes at the M06-2X/6-311G (d,p) and LANL2DZ/6–31 + G (d, p) levels of theory, respectively. The structural characteristics, charges (Mulliken and NPA), global reactivity descriptors, MEP, and dipole moments were investigated using this method. Furthermore, a molecular docking study predicted the interactions in the protein–ligand complex.