Mononuclear Compounds Research Articles

Organosulfonate‐Modulated Spin‐Crossover Behavior in Three Halogen‐Functionalized Cobalt(II) Complexes

AbstractWe present here the syntheses, crystal structures, and spin crossover (SCO) properties of a series of halogen‐functionalized cobalt(II) complexes, [Co(Brphtpy)2](OTf)2 ⋅ DMF ⋅ 2H2O (1), [Co(Brphtpy)2](HBS)2 ⋅ H2O (2), [Co(Brphtpy)2](MQ)2 ⋅ 2MeCN ⋅ 3H2O (3) (Brphtpy=4′–(4‐Bromophenyl)–2,2′:6′,2′′‐terpyridine; OTf−=trifluoromethanesulfonate; HBS−=hydroxybenzenesulfonate dihydrate; MQ−=methyl orange). Variable‐temperature single‐crystal X‐ray analyses revealed mononuclear compounds of 1–3 consisted of [Co(Brphtpy)2]2+ SCO active units and organosulfonate anions and no structural phase transformation happened in measured high‐low temperature. The packing structures of these complexes were tuned by varying organosulfonates. However, no notable supramolecular interactions can be found, in turn leading to gradual, incomplete, and non‐hysteretic SCO behaviors. Interestingly, the SCO behaviors of these three complexes were significantly modified after the removal of lattice solvents. Combined structural and magnetic investigations revealed the non‐cooperative supramolecular packing structures, guest internal pressure, and the small structural distortions of the SCO units should be responsible for the worse SCO properties of 1–3. The foregoing results show that to achieve high‐performance Co2+ SCO, both the weak interactions, internal pressure, and structural distortion should be considered during the design and construction of SCO complexes.

Enclathration of Mn(II)(H2O)6 guests and unusual Cu⋯O bonding contacts in supramolecular assemblies of Mn(II) Co-crystal hydrate and Cu(II) Pyridinedicarboxylate: Antiproliferative evaluation and theoretical studies

Two new coordination compounds of Mn(II) and Cu(II) involving 2,6-pyridinedicarboxylate viz. [Mn3(2,6-PDC)4(H2O)4][Mn(H2O)6]·8H2O (1) and [Cu(2,6-PDC)(H2O)(4-CNpy)]·H2O (2) (2,6-PDC = 2,6-pyridinedicarboxylate, 4-CNpy = 4-cyanopyridine) have been synthesized at room temperature. Compound 1 crystallizes as a co-crystal hydrate of Mn(II); whereas compound 2 is a mononuclear compound of Cu(II). Crystal structure analysis of 1 unfolds the presence of Mn(II)(H2O)6 guests within the supramolecular host cavities formed by anionic complex moieties and lattice water molecules. The lattice water molecules of the compounds 1 and 2 are involved in the formation of (H2O)2 cores which are enclathrated in the supramolecular host cavities. Furthermore, the unconventional anion⋯π, antiparallel CN⋯CN, CO⋯CO, CR⋯CR (CR: chelate ring) and Cu⋯O bonding interactions observed in compound 2 play crucial role to the stability of the crystal structure. Theoretical calculations confirm that the H-bonding network in 1 and anion-π, unconventional Cu···O bonds, antiparallel CO···CO along with CR···CR interactions in 2 play crucial roles in the solid state stability of the compounds. In vitro anticancer activities of the compounds considering cell viability and apoptosis assays against Dalton's lymphoma (DL) cancer cell lines reveal that the compounds induce considerable cytotoxicity in DL cells with negligible cytotoxicity in normal PBMC cells. Lactate dehydrogenase (LDH) leakage assay also unfolds the release of LDH from DL cells to extracellular space suggesting the irreversible cell death with cell membrane damage. The molecular docking simulations of the compounds further demonstrate the structure activity relationships involving the active sites of some important antiapoptotic proteins.

Synthesis and biological properties of palladium(II) cyclometallated compounds derived from (E)-2-((4-hydroxybenzylidene)amino)phenol

(E)-2-((4-hydroxybenzylidene)amino)phenol (iminophenol a) reacted with Pd(OAc)2 giving place to compound 1a, in which the iminophenol was bonded to palladium(II) in a κ3-Cortho,N,Oortho tridentate chelating mode. Thus, 1a was formed by neutral mononuclear units of schematic formula Pd(C,N,O), consisting of two fused five-membered metallacycles. Self-assembly of the Pd(C,N,O) units gave place to the polynuclear structure of 1a. Treatment of 1a with PPh3 or PPh2CH2CH2PPh2 in molar ratio Pd(II)/PPh3 = 1/1 or Pd(II)/PPh2CH2CH2PPh2 = 2/1 produced the mononuclear or dinuclear compound of schematic formula [Pd(C,N,O)(PPh3)] (2a) or {[Pd(C,N,O)]2(µ2-PPh2CH2CH2PPh2)} (3a), respectively. Compounds a were characterized by elemental analysis, high resolution ESI-(+) mass spectrometry, IR, and NMR. In addition, the crystal structure of the adducts 2a·2(CH2Cl-CH2Cl) and 3a·5(dmso) was determined by single crystal X-ray diffraction analysis. Most compounds a were noncytotoxic or poorly cytotoxic. Nonetheless, 2a was moderately cytotoxic against the MCF-7 breast and HCT-116 colon human cancer cell lines, and presented very low cytotoxicity towards normal skin human BJ cells. Compounds a showed moderate antibacterial activity against some Gram-positive (B. subtilis and S. aureus) and Gram-negative (E. coli) bacterial strains, and displayed also moderate antioxidant activity, producing 3a the best antioxidant activity. 1a changed the electrophoretic mobility of the pBluescript SK+ plasmid DNA. This change followed the pattern of cisplatin, but it started at a concentration twenty times higher than with cisplatin. Moreover, compounds 1a - 3a inhibited topoisomerase IIα at concentrations of 10, 50 and 25 µM, respectively.

Orthopalladated N,N-dimethyl-1-phenethylamine compounds containing 2,6-lutidine: Synthesis, DNA binding studies and cytotoxicity evaluation

Metathetical reactions involving [Pd(C2,N-dmpa)(μ-Cl)]2 (1) and the appropriate halides/pseudohalides salts afforded cyclopalladated dimers of the type [Pd(C2,N-dmpa)(μ-X)]2 (dmpa = S(−) enantiomer of N,N-dimethyl-1-phenethylamine; {X = Cl (1) and N3 (2)}. Mononuclear compounds of general formulae [Pd(C2,N-dmpa)(X)(lut)] {X = Cl (1a) and N3 (2a)} were obtained by bridge-splitting reactions involving the corresponding [Pd(C2,N-dmpa)(μ-X)]2 with 2,6-lutidine (lut) in the 1:2 M ratio at room temperature. Both the cyclopalladated compounds were characterized by means of elemental analysis, FT-IR, Raman, 1H and 13C NMR spectroscopy. The antiproliferative activity of the mononuclear compounds 1a-2a was evaluated towards human glioblastoma (U251 and T98G) and melanoma cell lines (HT144 and LB373) and their IC50 values determined between 1 and 6 μM. In most cases, the cytotoxic effects of compounds 1a-2a showed to be similar to those of cisplatin (depending on the cell line), what is of utmost importance when considering treatment alternatives for these aggressive tumor types. Binding studies on the representative compound 2a towards ct-DNA, however, showed low or no affinity, suggesting that the observed cytotoxicity against the human cell lines may involve different mechanisms of action compared to that of the platinum-based chemotherapy drug. The ability of 1a to induce the inhibition of topoisomerase IIα activity has also been investigated. These cyclopalladated compounds can be transported and distributed through the body by human serum albumin (HSA), as observed by competition and computational studies with the protein. These findings are very promising and have motivated further studies for the design of new and bioactive cyclopalladated compounds for future medicinal purposes.

X-ray structure and magnetic properties of a mononuclear complex and a 1D coordination polymer assembled by cobalt(II) ions and a flexible oxamate ligand

This work describes the synthesis, crystal structures and direct current (dc) magnetic properties of two air-stable oxamato-containing cobalt(II) complexes, [Co(H2edpba)(dmso)2]·dmso·H2O (1) and [Co(H2edpba)(H2O)2] n ·n(dmso) (2) [H4edpba = N,N′-2,2′-ethylenediphenylenebis(oxamic acid); dmso = dimethylsulfoxide]. 1 is a mononuclear compound, whereas 2 is a neutral chain. Cobalt(II) ions in both compounds are six-coordinate by six oxygen atoms, four of them from two monodeprotonated oxamate groups and the other two from dmso (1)/water (2) molecules in cis (1) and trans (2) positions. Hydrogen bonds between monodeprotonated oxamate fragments of adjacent mononuclear units in 1 lead to a supramolecular chain growing along the crystallographic c axis. Hydrogen bonds involving coordinated water molecules and monodeprotonated oxamate fragments from adjacent chains in 2 result in a supramolecular 2D network. Cryomagnetic measurements reveal the occurrence of magnetically isolated high-spin cobalt(II) ions in agreement with the large values of the shortest intramolecular (1)/intrachain (2) metal···metal separation [ca. 10.3 (1) and 10.4 Å (2)]. Simultaneous simulation of the χ M T versus T and M against H data through the Griffith–Figgis Hamiltonian led to the best-fit parameters: λ = −141.1 (1)/–174.8 cm−1 (2), σ = −1.45 (1)/–1.25 (2) and ν = −121.42 (1)/−247.29 cm−1 (2).

Zinc(II) Complexes with Triplet Charge-Transfer Excited States Enabling Energy-Transfer Catalysis, Photoinduced Electron Transfer, and Upconversion.

Many CuI complexes have luminescent triplet charge-transfer excited states with diverse applications in photophysics and photochemistry, but for isoelectronic ZnII compounds, this behavior is much less common, and they typically only show ligand-based fluorescence from singlet π–π* states. We report two closely related tetrahedral ZnII compounds, in which intersystem crossing occurs with appreciable quantum yields and leads to the population of triplet excited states with intraligand charge-transfer (ILCT) character. In addition to showing fluorescence from their initially excited 1ILCT states, these new compounds therefore undergo triplet–triplet energy transfer (TTET) from their 3ILCT states and consequently can act as sensitizers for photo-isomerization reactions and triplet–triplet annihilation upconversion from the blue to the ultraviolet spectral range. The photoactive 3ILCT state furthermore facilitates photoinduced electron transfer. Collectively, our findings demonstrate that mononuclear ZnII compounds with photophysical and photochemical properties reminiscent of well-known CuI complexes are accessible with suitable ligands and that they are potentially amenable to many different applications. Our insights seem relevant in the greater context of obtaining photoactive compounds based on abundant transition metals, complementing well-known precious-metal-based luminophores and photosensitizers.

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

Dinuclear Organoruthenium Complex for Mitochondria-Targeted Near-Infrared Imaging and Anticancer Therapy to Overcome Platinum Resistance

New mononuclear and dinuclear Ru(II) coordination compounds with the 2,7-bisbenzoimidazolyl-naphthyridine ligand have been synthesized and characterized by UV-vis, NMR, and MALDI-TOF. The molecular structures for Ru(II) compounds were determined by single-crystal X-ray diffraction. With the expansion of ligand π-conjugation and the increase in the complexed Ru number, the maximum emission wavelength red-shifted from 696 to 786 nm. The binding mode between complexes and DNA was predicted by molecular docking, which is intercalations and π-π stacking interactions with the surrounding bases. The intercalation mode of DNA binding was then determined by DNA titration and ethidium bromide (EB) displacement experiments. The antigrowth effects of complexes RuY, RuY1, and RuY2 were tested in HaCat (normal cells), HeLa (cervical cancer), A549 (lung cancer), and A549/DDP (cisplatin-resistant lung cancer) through the MTT assay. The dinuclear complex RuY2 was superior to mononuclear complexes and cisplatin in the cisplatin-resistant cell line. Confocal imaging proved that the subcellular localization of Ru(II) complexes was mitochondria; moreover, apoptosis was detected by flow cytometry. All three complexes showed a dose-dependent manner in all four cell lines. All Ru(II) complexes were found to have reactive oxygen species (ROS). The finding indicated that these Ru(II) complexes caused cell death by both DNA disruption and ROS. This study helps to explore the potential of the polynuclear Ru(II) complexes for the combination of NIR imaging and Pt-resistant cancer therapy.

Synthesis and properties of binuclear ferrocene energetic compounds as combustion rate catalyst

AbstractIn order to improve the catalytic performance, oxidation resistance and thermal stability of neutral alkyl ferrocene‐based combustion rate catalysts, mononuclear ferrocene energetic compounds were designed and prepared, but four binuclear ferrocene energetic compounds were unexpectedly discovered during the synthesis compounds. The new compounds were characterized by single‐crystal X‐ray diffraction,1H and13C nuclear magnetic resonance spectroscopy, and high‐resolution mass spectrometry. The crystal structures of compoundsa,b,canddconfirmed that we have successfully prepared binuclear ferrocene nitrogen‐containing heterocyclic compounds. The thermogravimetric results revealed that most of the compounds exhibit high thermal stability. The electrochemical properties of the four compounds were examined by cyclic voltammetry (CV) and differential pulse voltammetry; the CV experimental results indicated that these compounds showed good electrochemical performance, which contributed to their burning rate catalytic activity in composite solid propellants. Differential scanning calorimetry was used to study the catalytic performance of the binuclear ferrocene energetic compounds for ammonium perchlorate (AP). The results show that these compounds have a good combustion catalytic effect on AP due to the increase in the number of ferrocene groups.

Inside Back Cover: Self‐Assembly of Molecular Trefoil Knots Featuring Pentadecanuclear Homoleptic AuI‐, AuI/AgI‐, or AuI/CuI‐Alkynyl Coordination (Angew. Chem. Int. Ed. 21/2022)

Molecular trefoil knots are usually covalently assembled from rationally designed building blocks with multiple functional groups. In their Research Article (e202200748), Jie-Sheng Huang, Chi-Ming Che, and co-workers report on the use of monoalkynes and a mononuclear AuI compound for the self-assembly of Au−C bonded Au15 trefoil knots featuring non-covalent AuI–AuI interactions. The structures, solution behavior, and photoluminescence properties of the Au15 and Au9M6 (M=Cu/Ag) trefoil knots were studied.

Reactivity between late first-row transition metal halides and the ligand bis(2-pyridylmethyl)disulfide: Vibrantly-colored compounds with variable molecular geometries influenced by metal-sulfur interactions

The reactivity between late first-row transition metal halides and the disulfide-containing ligand bis(2-pyridylmethyl)disulfide was examined. From this survey, a series of mononuclear, four- and five-coordinate metal compounds were prepared and characterized. Single-crystal X-ray diffraction was employed to analyze the molecular structures in the solid state. The four-coordinate, tetrahedral compounds adopt either the form MLX2 (M = Zn; L = bis(2-pyridylmethyl)disulfide; X = Cl, Br) where the disulfide ligand is coordinated in a bidentate fashion by two nitrogen donors, or MLX (M = Cu; L = bis(2-pyridylmethyl)disulfide; X = Cl, Br) where the ligand is tridentate, coordinating via one sulfur and two nitrogen donors. The five-coordinate metal compounds, though varying significantly with regard to molecular geometry due to metal-sulfur interaction strength, adopt the form MLX2 (M = Zn, Cu, Co; L = bis(2-pyridylmethyl)disulfide; X = Cl, Br) with the ligand serving as a tridentate scaffold employing one sulfur and two nitrogen donors. The crystal structures ZnLCl2•CHCl3 and ZnLBr2•CHCl3 are isomorphous as are the structures ZnLCl2•CH2Cl2, ZnLBr2•CH2Cl2, and CoLBr2•CH2Cl2. The crystal structure of CoLCl2 is a kryptoracemate, having an enantiomeric pair within the asymmetric unit. Although chemically-identical, both hands of CoLCl2 have strikingly different Co–S distances: 2.599(2) versus 2.755(2) Å. Based on the X-ray crystal structures, the choice of halide does not appear to significantly influence the molecular geometry. For the solvated crystal structures, the identity of the solvent molecule has a drastic effect on the metal-sulfur distances. Compounds that contain metal-sulfur coordination do not appreciably affect the disulfide bond, as determined by X-ray crystallography and Raman spectroscopy. In addition to the standard analytical methods, variable-temperature NMR and UV–vis–NIR spectroscopy was utilized to gain insight into the solution behavior of the vibrantly-colored compounds.

An 8-hydroxyquinoline-N-oxide manganese(II) complex induces apoptosis of A549/DDP cells by disrupting the mitochondrial pathway

• • Mn(II) complex 1 with 8-hydroxyquinoline-N-oxide was firstly synthesized. • • Mn(II) complex 1 showed high in vitro antitumor activity toward A549/DDP cells. • • Mn(II) complex 1 can cause mitochondrial dysfunction. A new manganese(II) complex bearing an 8-hydroxyquinoline- N -oxide (HNQ) ligand, i.e., [Mn(HNQ) 2 (CH 3 OH) 2 Cl 2 ] ( 1 ), was synthetized and fully characterized by single-crystal X-ray diffraction, infrared spectroscopy, electrospray ionization mass spectrometry, and elemental analysis, which revealed that Mn(II) complex 1 is a six-coordinated mononuclear compound. The anticancer activity of Mn(II) complex 1 against A549/DDP and A549 cancer cells and HL-7702 normal cells was tested and compared with that of MnCl 2 ⋅4H 2 O, cisplatin, and HNQ. Mn(II) complex 1 displayed potent cytotoxic activity, especially against A549/DDP tumor cells, with IC 50 values of 0.02 ± 0.01 μM, whereas it was practically inactive against HL-7702 normal cells. Mechanistic studies indicated that the cytotoxic activity of Mn(II) complex 1 proceeds via induction of mitochondria-mediated intrinsic apoptosis in A549/DDP cells.

Immobilization mechanism of antimony by applying zirconium‐manganese oxide in soil

Antimony (Sb) accumulation in soil poses great potential risk to ecological environment, and its mobilization, transformation and bioavailability are controlled by its fractions and species. Hence, it is important to develop functional materials with both adsorption and oxidation that achieve detoxification and control the mobilization of Sb. In this study, the synthesized zirconium‑manganese oxide (ZrMn) could extremely promoted the transformation of antimonite [Sb(III)] to antimonate [Sb(V)], induced the bioavailable Sb shift to well-crystallized (hydr)oxides of Mn and residual fractions, and further reduced mobility and bioavailability Sb in soil. The sorption of ZrMn to Sb(III) and antimonate Sb(V) were affected by interfering ions, and to Sb(III) was a heterogeneous adsorption process. Spectroscopic characterization of XPS and FTIR suggested exchange between the hydroxyl groups and Sb was crucial in its retain and forming an electronegative inner-sphere mononuclear or binuclear bridging compound. The oxidation induced the transformation of Mn species in ZrMn, generated Mn(II) and Mn(III) exposing more reactive sites conducive to oxidation and adsorption, thus Mn oxides has a higher adsorption capacity for Sb(III). However, the Zr oxides of ZrMn presented adsorption rather than oxidation. The application of ZrMn could realize the dual effect of Sb oxidation detoxification and adsorption immobilization in soil, which provided references for Sb contaminated soil remediation.

Role of hydrazone substituents in determining the nuclearity and antibacterial activity of Zn(II) complexes with pyrazolone-based hydrazones.

Hydrazones and their metal derivatives are very important compounds in medicinal chemistry due to their reported variety of biological activities, such as antibacterial, antifungal and anticancer action. Five hydrazone-pyrazolone ligands H2Ln (n = 1-5) were prepared and fully characterized and their tautomerism was investigated in the solid state and solution. Five zinc(II) complexes 1-5 of composition [Zn(HLn)2] (n = 1 and 2), [Zn(HLn)2(H2O)2] (n = 3 and 5) and [Zn(HL4)2]n were synthesized and characterized by elemental analysis, IR, 1H, 19F, 13C, and 15N NMR spectroscopy, and ESI mass spectrometry. In addition, the structures of two ligands and three complexes were determined by single-crystal X-ray diffraction. The ligands H2L2 and H2L4 exist both in the NH,NH tautomeric form. Complexes 1 and 2 are mononuclear compounds, while complex 4 is a one-dimensional coordination compound. Density functional theory (DFT) calculations were carried out on proligands, their anions and all zinc complexes, confirming the experimental results, supporting IR and NMR assignments and giving proofs of the mononuclear diaqua structure of complexes 3 and 5. The antibacterial activity of the free ligands and the Zn(II) complexes was established against Escherichia coli and Staphylococcus aureus, and a strong efficiency has been found for Zn(II) complexes, particularly for the polynuclear 4 and the mononuclear diaqua complex 5, the latter containing a ligand with aliphatic and fluorinated substituents able to compromise the permeability of and disrupt the bacterial cell membrane.

Orthopalladated tetralone oxime compounds bearing tertiary phosphines: Synthesis, structure, biological and in silico studies

The halido-α-bridge cleavage reactions between [Pd(C2,N-tetrox)(μ-Cl)]2 precursor (tetrox = E-α-tetralone oxime) with phosphines, in 1:2 molar ratio, have afforded mononuclear cyclopalladated compounds of the type [PdCl(C2,N-tetrox)(L)] {L = triphenylphosphine (1); tris(4-methylphenyl)phosphine (2); tris(4-fluorophenyl)phosphine (3) and tris(4-methoxyphenyl)phosphine (4)}. The compounds have been characterized by elemental analyses, infrared (FT-IR) and 1H, 13C{1H} and 31P{1H}-NMR spectroscopies. The molecular structure of 3 has been determined by single crystal X-ray diffraction (SC-XRD) and the Hirshfeld Surface calculation (HS) has been performed. The antiproliferative activity of compounds 1–4 has been evaluated against breast (MCF-7) and lung (A549) human cancer cells, and human lung fibroblast (MRC-5). All cyclopalladated compounds have been more active than cisplatin against MCF-7 cells, with IC50 values ranging from 19 to 26 µM. Binding experiments involving compound 3 with ct-DNA and human serum albumin (HSA) have been carried out using spectroscopic techniques. The interaction between compound 3 and HSA has been studied by means of molecular docking.

One-pot solvothermal synthesis of mononuclear and oxalate-bridged binuclear nickel compounds: Structural analyses, conformation alteration and magnetic properties

Two new discrete compounds with the formula [Ni(3,5,6-tcpa)(2,2′-bipy)Cl] (1) and [Ni2(3,5,6-tcpa)2(2,2′-bipy)2(ox)]·2EtOH (2) (3,5,6-Htcpa = 2-((3,5,6-trichloro pyridin-2-yl)oxy)acetic acid, 2,2′-bipy = 2,2′-bipyridine, ox = oxalate dianion) have been co-synthesized under solvothermal conditions in the same medium. Single-crystal X-ray diffraction analysis shows that both 1 and 2 have crystallized in triclinic system, space group P1¯ and the central NiII ions are both in deformed square–pyramids. The NiII ion in 1 was bonded by one chloride ion (Cl-), one bidentate chelate 3,5,6-tcpa anion and one 2,2′-bipy to give a mononuclear complex 1. While for 2, the NiII ion was coodinated with one monodentate 3,5,6-tcpa, one oxalate anion and one 2,2′-bipy. The oxalate anion linked two equivalent NiII ions to form the binuclear cluster 2. The Cl···Cl halogen bonds, π···π stacking interactions and/or OH···O hydrogen bonds play an important part in the crystal packing for 1 and 2. Their deeply structural analyses revealed that the similar structure features and conformation alteration of 3,5,6-tcpa may be responsible for the cocrystallization phenomenon of 1 and 2. The magnetic measurements indicated the presence of intramolecular weak ferromagnetic coupling with J = 1.02 cm−1 in 2.

Elucidating the contribution of solvent on the catecholase activity in a mononuclear Cu(II) system: An experimental and theoretical approach

• A mononuclear copper(II) complex, [Cu(H 2 tea)(N 3 )] (T-2) is synthesized and characterized. • The present complex exhibited excellent solvent dependent catecholase activity with K cat(MeOH) = 903.6 h ‒1 . • Highest catalytic efficiency is observed in MeOH followed by MeCN. • The catecholase activity is corroborated by DFT calculations. • The HOMO-LUMO energy gap and charge distribution govern the activity. A new mononuclear copper(II) complex, [Cu(H 2 tea)(N 3 )] (T-2) is synthesized and characterized by crystallographic, spectral and theoretical studies. The synthesized complex adopts penta coordinate tbp geometry around the Cu(II) center. The ligand (triethanolamine, H 3 tea) binds the metal as monoanionic species (H 2 tea ‒ ). Supporting ligand (N 3 ‒ ) satisfies the coordination geometry through monodentate mode. Several non-covalent interactions (such as O—H and N—H) integrate the whole framework and these interactions are well quantified with Hirshfeld surface analysis. The present complex exhibited excellent catecholase activity (solvent dependent) with K cat(MeOH) = 903.6 h ‒1 . UV-Visible spectral study indicated a notable effect of solvent nature on the catecholase activity of Cu(II) complex which is attributable to the coordinating capability of the diverse solvents used. The maximum catalytic efficiency is observed in MeOH and then tailed by MeCN for T-2; while no such activity in DMSO was observed. The catecholase activity of T-2 is well corroborated by DFT calculations which reveal that higher difference in charge contributions between HOMOs and LUMOs along with metal and ligands of copper complex is the factor to the enhanced catecholase activity. The present work deals with the determination of structure-activity interrelation of mononuclear coordination compounds. A Cu(II) complex exhibits excellent solvent dependent catecholase activity as corroborated experimentally and theoretically.

STRUCTURAL FEATURES, COMPUTATIONAL STUDIES AND BIOLOGICAL ANALYSIS: SCHIFF’S BASE LIGAND AND ITS COORDINATION COMPOUNDS

Structure and biological application based analysis has been carried out for Schiff’s base ligand containing nitrogen and sulphur donor atoms and also for a series of its coordination compounds. Ligand benzil-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L) has been prepared and structural features of ligand investigated by elemental analyses, IR, 1 H-NMR, mass spectra and molecular modeling studies. The chemical reaction of the prepared ligand with metal ions afforded mononuclear coordination compounds of Mn(II) and Co(II) metal ions. The characterization of the coordination compounds is being based on the techniques i.e. elemental analysis, infra-red, UV-visible as well as melting point, molar conductivity and magnetic moment measurement. A computational study has been done to understand the miscellaneous coordination modes of ligand to metal ions. Characterization result shows that coordination compounds exhibit a six coordinated geometrical arrangement i.e. octahedral geometry. The biological inhibition zone (antifungal and antibacterial activities) of synthesized compounds, i.e. ligand and its coordination compounds, has been monitored using well diffusion technique

Bromination and C–C Cross-Coupling Reactions for the C–H Functionalization of Iridium(III) Emitters

The orthometalated phenyl groups of the dimer [Ir(μ-Cl){κ2-C,N-(C6H3Me-py)}2]2 have been selectively brominated, at para-position with regard to the Ir–C bonds, with N-bromosuccinimide. The bromination leads to [Ir(μ-Cl){κ2-C,N-(C6H2MeBr-py)}2]2, which affords the mononuclear derivatives Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-O,N-[OC(O)-py]}, Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-O,O-(acac)}, and Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-C,N-[C6H4-Mepy]} by replacement of the chloride bridges by a picolinate anion, an acac group, and an orthometalated 2-phenyl-5-methylpyridine ligand, respectively. Complexes Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-O,O-(acac)} and Ir{κ2-C,N-(C6H2MeBr-py)}2{κ2-C,N-[C6H4-Mepy]} have been subsequently postfunctionalized by means of palladium-catalyzed Suzuki–Miyaura cross-coupling to give Ir{κ2-C,N-(C6H2MeR-py)}2{κ2-O,O-(acac)} (R = Me, Ph) and Ir{κ2-C,N-(C6H2Me2-py)}2{κ2-C,N-[C6H4-Mepy]}. These [3b + 3b + 3b′] mononuclear compounds are green-yellow emitters (488–580 nm) upon photoexcitation, in doped poly(methyl methacrylate) (PMMA) film at 5 wt % at room temperature and 2-methyltetrahydrofuran (2-MeTHF) at room temperature and at 77 K. They display lifetimes in the range 1.0–5.0 μs and quantum yields in PMMA films and in 2-MeTHF at room temperature between 0.84 and 0.40.

Four new CuI/AgI-based coordination compounds containing 2-mercapto-5-methyl-1,3,4-thiadiazole: Synthesis, crystal structures and fluorescence properties

Effectively constructing CuI/AgI-based coordination polymers containing Hmthd ligands is a challenging work, here, four new coordination compounds [Cu(Hmthd)2Cl]n (1), [Cu3(mthd)2Br]n (2), [Ag(mthd)]n (3) and [Ag2(mthd)I]n (4) have been obtained by reactions of the corresponding metal salts and 2-mercapto-5-methyl-1,3,4-thiadiazole (Hmthd) ligand under solvothermal conditions. All the compounds were fully characterized by single-crystal X-ray diffraction, elemental analysis, IR spectrum, thermalgravimetric analysis and powder X-ray diffraction. Compound 1 is a mononuclear coordination compound, in which two neutral Hmthd molecules and CuCl unit are coplanar. In compound 2, the anionic [CuBr(mthd)]22– units and one-dimensional coplanar cationic {[Cu2(mthd)]+}n chains are connected to each other to form a two-dimensional layered structure. In compound 3, two different one-dimensional puckered [Ag(mthd)]n chains are connected to each other to form a two-dimensional irregular layered structure, in which a (AgS)n chain constructed by staggered Ag3S3 rings is observed. Compound 4 is a two-dimensional double layer coordination framework containing a two-dimensional inorganic (Ag2IS)n double layer. Compound 4 shows the apparent yellow emission with the maximum at 551 nm while exciting at 333 nm, and displays sensitive luminescence quenching response to nitrobenzene with quenching constant (Ksv) of 5.07 × 103 M−1 and detection limit of 5.33 × 10−6 M. This research provides a new strategy to construct the CuI/AgI-based coordination compounds containing Hmthd ligands with extended structures through the synergistic effect of (mthd)- and halide ions.