Mononuclear Coordination Complexes Research Articles

Unprecedented Coordination Compounds with 4,4′-Diaminodiphenylethane as a Supramolecular Agent and Ditopic Ligand: Synthesis, Crystal Structures and Hirshfeld Surface Analysis

In this pioneering research, mononuclear coordination complexes and coordination polymers were obtained using the conformationally flexible ditopic ligand 4,4′-diaminodiphenylethane and different metal salts (nitrates, sulfates, tetrafluoroborates and perchlorates). Seven new products, including the mononuclear complexes [Cd(2,2′-bpy)3](ClO4)2](dadpe)(4,4′-bpy) (1), [Ni(dadpe)2(H2O)4](SO4).H2O (2), one-dimensional coordination polymers {[Zn(NO3)(dadpe)(dmf)2](NO3)}n (3), {[Cd(2,2′-bpy)2(dadpe)](ClO4)2}n (4), and two-dimensional coordination polymers, {[Cd(4,4′-bpy)2(H2O)2](ClO4)2(dadpe)(EtOH)2}n (5), {[Co(4,4′-bpy)2(H2O)2](BF4)2(dadpe)(EtOH)2}n (6) and {[Cd(adi)(dadpe)](H2adi)}n (7), (dadpe=4,4′-diaminodiphenylethane, 2,2′-bpy=2,2′-bipyridine, 4,4′-bpy=4,4′-bipyridine, H2adi=adipic acid) were produced. The synthesized compounds were characterized by FTIR and single-crystal X-ray diffraction analyses. The dadpe was recorded as a neutral guest in the crystals of mononuclear complex 1 and in coordination polymers 5 and 6. In compound 2, two dadpe ligands coordinate in a monodentate mode and occupy two trans-positions in the [Ni(H2O)4(dadpe)2]2+ octahedral complex cation. Coordination polymers 3 and 4 represent single chains originating from dadpe as a bidentate linker in both. The H-donor’s possibilities of amino groups were utilized in the interconnection of coordination chains into H-bonded networks via NH(NH2)···O hydrogen bonds. The isostructural coordination polymers 5 and 6 comprise similar cationic square grids [M(4,4′-bpy)2(H2O)2]2+ [M=Cd (5), M=Co (6)], with sql topology balanced by the charge-compensated anions, while dadpe and EtOH as neutral guests are situated in the interlayer space. The neutral 2D coordination network in 7 with the sql topology originates from both adi and dadpe linkers as bidentate-bridging ligands, and the neutral H2adi is entrapped as a guest in crystal lattice. The impact of different types of intermolecular interactions was evaluated by Hirshfeld surface analysis.

Crystalline Molecular Assemblies of Complexes Showing Eightfold Coordinated Niobium(IV) Dodecahedral Geometry in the Pyridine-Dicarboxylic Acid System.

The reactivity of 2,3-pyridine-dicarboxylic (known as quinolinic or H2qui) acid and 2,5-pyridine-dicarboxylic (known as isocinchomeronic or H2icc) acid has been investigated as a complexing agent toward the niobium(IV) tetrachloride precursor (NbCl4·2THF) in different organic solvent mixtures. It resulted in the isolation of four crystalline assemblies of mononuclear coordination complexes 1-4 [Nb(HL)4·solvent], where HL is the monoprotonated quinolinate (Hqui) ligand (complexes 1-3) or the monoprotonated isocinchomeronate ligand (complex 4). For each complex, the discrete niobium(IV) center is eightfold coordinated to four oxygen atoms from the deprotonated carboxylate arm and four nitrogen atoms from the pyridine part of the dicarboxyl ligand with a dodecahedral environment [NbO4N4]. The remaining carboxyl arm (either in 3 or in 5 position) remained under its protonated form, leading to neutral [Nb(HL)4] moieties for compounds 1, 2, and 4, or the anionic [Nb(qui)(Hqui)3]- moiety for compound 3. The complexes are observed in various molecular arrangements, involving intercalated solvent molecules such as acetonitrile in compound 1 ([Nb(Hqui)4·0.8(CH3CN)], obtained at room temperature), a mixture of acetonitrile and pyridine in compound 2 ([Nb(Hqui)4·0.7CH3CN·2PYR], obtained via the solvothermal reaction at 80 °C), a mixture of pyridine and triethylamine, in addition with water and chloride species, in compound 3 ([Nb(qui)(Hqui)3·Cl·HPYR·HTEA·1.5H2O], obtained via solvothermal reaction at 80 °C), and N,N-dimethylformamide in compound 4 ([Nb(Hicc)4·6DMF], obtained at room temperature). The d1 configuration expected for the niobium(IV) centers has been analyzed by magnetic measurements, as well as by EPR and XPS. An anti-ferromagnetism transition has been observed at very low temperatures for complexes 1 (3.6 K) and 4 (3.3 K), for which the shortest Nb···Nb interatomic lengths occur.

Ancillary ligand-assisted self-assembly of a pyrenylpyridine with Zn(II), Cu(II), Ni(II), and Co(II): Syntheses, structural characterization, and photoluminescence properties

4-(Pyren-1-yl)pyridine (L) with luminescence properties was self-assembled with β-diketone-based transition metal compounds to produce five new hexacoordinated metal complexes: [Zn(acac)2L2] (1), [Zn(hfacac)2L2] (2), [Ni(hfacac)2L2] (3), [Cu(hfacac)2L2] (4), and [Co(acac)2L2] (5) [L = 4-(pyren-1-yl)pyridine, acac = acetylacetone, and hfacac = hexafluoroacetylacetone]. The structures of these complexes were characterized by single-crystal and powder X-ray diffractometry; elemental analysis; electrospray ionization masss pectrometry; and nuclear magnetic resonance, infrared, and fluorescence spectroscopies. The β-diketone ancillary ligands and pyrenylpyridine functional ligands were bonded to Zn(II)/Ni(II) /Cu(II)/Co(II) metal ions in an O^O and two N chelating fashion, leading to the formation of mononuclear coordination complexes where one-dimensional chains and two-dimensional sheet structures were formed via π···π stacking and hydrogen bonding interactions. In addition, the solid state photoluminescence properties of these new crystalline materials were examined, with obvious differences observed between the metal complexes.

Supramolecular cis-“Bis(Chelation)” of [M(CN)6]3− (M = CrIII, FeIII, CoIII) by Phloroglucinol (H3PG)

Studies on molecular co-crystal type materials are important in the design and preparation of easy-to-absorb drugs, non-centrosymmetric, and chiral crystals for optical performance, liquid crystals, or plastic phases. From a fundamental point of view, such studies also provide useful information on various supramolecular synthons and molecular ordering, including metric parameters, molecular matching, energetical hierarchy, and combinatorial potential, appealing to the rational design of functional materials through structure–properties–application schemes. Co-crystal salts involving anionic d-metallate coordination complexes are moderately explored (compared to the generality of co-crystals), and in this context, we present a new series of isomorphous co-crystalline salts (PPh4)3[M(CN)6](H3PG)2·2MeCN (M = Cr, 1; Fe, 2; Co 3; H3PG = phloroglucinol, 1,3,5-trihydroxobenzene). In this study, 1–3 were characterized experimentally using SC XRD, Hirshfeld analysis, ESI-MS spectrometry, vibrational IR and Raman, 57Fe Mössbauer, electronic absorption UV-Vis-NIR, and photoluminescence spectroscopies, and theoretically with density functional theory calculations. The two-dimensional square grid-like hydrogen-bond {[M(CN)6]3−;(H3PG)2}∞ network features original {[M(CN)6]3−;(H3PG)4} supramolecular cis-bis(chelate) motifs involving: (i) two double cyclic hydrogen bond synthons M(-CN⋅⋅⋅HO-)2Ar, {[M(CN)6]3−;H2PGH}, between cis-oriented cyanido ligands of [M(CN)6]3− and resorcinol-like face of H3PG, and (ii) two single hydrogen bonds M-CN⋅⋅⋅HO-Ar, {[M(CN)6]3−;HPGH2}, involving the remaining two cyanide ligands. The occurrence of the above tectonic motif is discussed with regard to the relevant data existing in the CCDC database, including the multisite H-bond binding of [M(CN)6]3− by organic species, mononuclear coordination complexes, and polynuclear complexes. The physicochemical and computational characterization discloses notable spectral modifications under the regime of an extended hydrogen bond network.

Coordination complexes constructed from pyrazole-acetamide and pyrazole-quinoxaline: effect of hydrogen bonding on the self-assembly process and antibacterial activity.

Two mononuclear coordination complexes of N-(2-aminophenyl)-2-(5-methyl-1H-pyrazol-3-yl)acetamide (L1), namely [Cd(L1)2Cl2] (C1) and [Cu(L1)2(C2H5OH)2](NO3)2 (C2) and one mononuclear complex [Fe(L2)2(H2O)2](NO3)2·2H2O (C3), obtained after in situ oxidation of L1, have been synthesized and characterized spectroscopically. As revealed by single-crystal X-ray diffraction, each coordination sphere made of two heterocycles is completed either by two chloride anions (in C1), two ethanol molecules (in C2) or two water molecules (in C3). The crystal packing analysis of C1, C2 and C3, revealed 1D and 2D supramolecular architectures, respectively, via various hydrogen bonding interactions, which are discussed in detail. Furthermore, evaluation in vitro of the ligands and their metal complexes for their antibacterial activity against Escherichia coli (ATCC 4157), Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923) and Streptococcus fasciens (ATCC 29212) strains of bacteria, revealed outstanding results compared to chloramphenicol, a well-known antibiotic, with a normalized minimum inhibitory concentration as low as 5 μg mL−1.

Fe(II) Spin Crossover/Polymer Hybrid Materials: Investigation of the SCO Behavior via Temperature-Dependent Raman Spectroscopy, Physicochemical Characterization and Migration Release Study.

Polymeric composites constitute an appealing class of materials with applications in various fields. Spin crossover (SCO) coordination complexes are switchable materials with potential use in data storage and sensors. Their incorporation into polymers can be considered an effective method for their wider practical application. In this study, Fe(II) SCO/polylactic acid hybrid polymeric composites have been prepared by film casting. The mononuclear coordination complex [Fe{N(CN)2}2(abpt)2] was incorporated into polylactic acid. The morphological, structural and thermoanalytical characterization of the composite films were performed via scanning electron microscopy (SEM), attenuated total reflectance (ATR/FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). In addition, the migration release study (MRS) of the SCO compound from the polymeric matrix into the food simulant 50% v/v water/ethanol solution was also examined via UV/Vis absorption. Of particular interest was the investigation of the SCO behavior of the coordination complex after its incorporation into the polymer matrix; it was accomplished by temperature-dependent micro-Raman spectroscopy. The described attempt could be considered a preparatory step toward the development of SCO-based temperature sensors integrated into food packaging materials.

New Mononuclear Complex of Europium(III) and Benzoic Acid: From Synthesis and Crystal Structure Solution to Luminescence Emission

This study presents a general method which can be used for the synthesis of mononuclear complexes with europium(III) and organic ligands with carboxylic groups. It describes the procedure for preparing a new mononuclear coordination complex with europium(III) and carboxylate ligands sourced from benzoic acid. The construction of mononuclear complexes with a coordination sphere saturated in carboxylic ligands must go through the preparation and purification of a europium(III) intermediate complex that presents a coordination sphere with anions that will be later exchanged for carboxylic groups and finally precipitated as a solvent-free or anion-free complex within the coordination sphere. The detailed synthesis procedure for powders of a new complex, as well as studies of its structural composition at each phase and luminescent properties, are detailed in this study. Analytical and spectroscopic data reveal the formation of a new mononuclear complex of the general formula [Eu(OOCC6H5)3·(HOOCC6H5)2]. The crystal structure of the Eu(III) complex was solved using X-ray powder diffraction data and EXPO2014 software, and the crystal structure result was deposited in the CCDC service with number 19771999.

Supramolecular inorganic chemistry leading to functional materials

Functional inorganic materials are very important today to meet the needs of our society. The most demanding needs are sustainable and clean energy (it would be nice if that can be achieved from water splitting), smart materials for sensing toxic volatile as well as water-soluble substances (health care) and efficient catalysts that can cycle multiple times without deterioration for useful chemical reactions. Supramolecular chemistry, that plays a vital role to design and synthesize such functional molecules, controls over the intermolecular interactions, thereby the molecular recognition processes leading to molecular functions, e.g., sensing, catalysis, etc. This article deals with inorganic supramolecular chemistry of a number of mono-nuclear coordination complexes to selected di-nuclear systems through trinuclear metal basic carboxylates, mostly in their solid-state, leading to the functional inorganic materials. We have demonstrated that some of the very old inorganic systems can be explored in the light of supramolecular chemistry to describe them as functional materials, which have potential in serving our society to some extent. This work aims to discuss the potential applications of some of the age-old chemical systems which can be broadly classified as mononuclear complexes, dinuclear systems and trinuclear clusters. These systems can be perceived as a seedling which has the potential to grow into a tree, provided, it is supplied with all the resources and well taken care of. By the virtue of extensive research going around the world, these versatile systems have evolved through the years to grow into a field with wide-ranging applications, but still a lot remains to be explored.

A series of Wells-Dawson and Keggin-based compounds with uncoordinated S donors as fluorescence sensors to Hg2+

Through using a S-containing ligand 2,2’-dimethyl-4,4’-bithiazole (dbt), a series of Wells-Dawson and Keggin-based compounds, {Zn(dbt)3}{Zn(dbt)2(H2O)}2{HP2WVWVI17O62}·4H2O (1), {Cd(dbt)2(H2O) (HP2WVWVI17O62)}{Cd(dbt)3}{Cd(dbt)2(H2O)}·13H2O (2), {Cd2(dbt)4Cl} {PW12O40} (3) and {Cd2(dbt)4}{SiW12O40} (4), were synthesized under hydrothermal conditions and structurally characterized. In 1, there are three dissociated subunits: Wells-Dawson anion, {Zn(dbt)3}2+ and {Zn(dbt)2(H2O)}2+. In 2, the mono-supporting Wells-Dawson anions exhibit abundant hydrogen bonding interactions with discrete {Cd(dbt)3}2+ and {Cd(dbt)2(H2O)}2+ mononuclear coordination complexes, constructing a supramolecular layer. Compound 3 has a binuclear Cd cluster {Cd2(dbt)4Cl}4+ with a Cl as a bridging atom. The Keggin anions link these binuclear Cd clusters alternately to build a 1D chain. In 4, a pair of {Cd(dbt)2}2+ subunits connect adjacent Keggin anions and a 1D chain is formed. In these four compounds, only the N donors coordinate with Zn or Cd and the S atoms are uncoordinated. These compounds show good fluorescence sensing performance to Hg2+. We also studied the electrochemical and photocatalytic properties of 1–4. These compounds also can act as electrochemical sensors for the detection of nitrite.

New Cobalt(II) and Copper(II) Thiocyanate Complexes of 2,5‐Bis(pyridin‐2‐yl)‐1,3,4‐oxadiazole Ligand: Synthesis, Crystal Structures, Spectral Properties and Hirshfeld Surface Analysis

AbstractThe synthesis and characterization of two new mononuclear coordination complexes based on 2,5‐bis(pyridin‐2‐yl)‐1,3,4‐oxadiazole (bpox) and thiocyanate ion as coligand, [M(bpox)2(SCN)2]nH2O (M=Co, n=1 for complex 1; M=Cu, n=0 for complex 2), are described. The obtained complexes crystallize in the monoclinic crystal system with space group C 2/c for complex 1 and P 21/n for complex 2. UV/Vis, FTIR and Raman data indicated the presence of bpox and thiocyanate groups, in isolated compounds. This finding has been confirmed by crystallographic studies, which shows that the two metals Co(II) and Cu(II), have an octahedral environment in complex 1 and complex 2, respectively, with both bpox ligands in equatorial sites and terminal SCN− in axial positions. The crystal structure cohesion of each compound is ensured by intramolecular metal‐nitrogen M–N (M= Co, Cu) interactions, by π–π stacking interactions and by different intermolecular‐hydrogen bonds, such as C–H⋯π, O–H⋯N, O–H⋯O, C–H⋯N, and/or C–H⋯S. The three‐dimensional Hirshfeld surface analysis and the two‐dimensional fingerprint plots reveal that the structure is dominated by C⋯H/H⋯C contacts.

Cu(II) and Mn(II) coordination complexes constructed by C linked bispyrazoles: Effect of anions and hydrogen bonding on the self assembly process

The reaction of 1,5,5′-trimethyl-1H,1′H-3,3′-bipyrazole (Hbpz) with copper and manganese salts (Cu(BF4)2·6H2O, MnCl2·4H2O and Mn(NCS)2) leads to the formation of three mononuclear coordination complexes [Cu(Hbpz)3](BF4)2(1), [Mn(Hbpz)2Cl2]·CH3CN (2) and [Mn(Hbpz)2(NCS)2]·Et2O (3). These compounds have been characterized using single crystal X-ray diffraction and infrared spectroscopy. The single crystal structures of 1, 2 and 3 are discussed in the context of the effect of hydrogen bonding functionalities and counter anions on the supramolecular structural diversities observed in these new coordination complexes.

Novel class of mononuclear 2-methoxy-4-chromanones ligated Cu (II), Zn (II), Ni (II) complexes: synthesis, characterisation and biological studies

Abstract Two new 2-methoxy -4-chromanones were synthesized from 3-formylchromone and 2-aminopyridine/2-amino-5-nitropyridine in methanolic media and was characterised using various spectral and analytical techniques. Reactions of these ligands with copper (II), zinc (II) and nickel (II) acetates lead to the formation of a novel class of mononuclear co-ordination complexes. Synthesized complexes were structurally characterised using elemental analysis, IR, UV-Vis, EPR, thermo gravimetric analysis, conductivity studies, magnetic measurements and proton NMR. Spectroscopic analysis reveals that ligand behaves bidendately. The complexes were tested for their binding ability with HS-DNA and found to be intercalative. Complex NiL1 was found to possess the highest Kb value (5.1 × 105). The α-amylase and α-glucosidase inhibition ability of ligands and complexes were also explored. The tested compounds were found to be mild α-amylase inhibitors and strong α-glucosidase inhibitors, characteristically similar to most of the antidiabetic drugs. Among the synthesized compounds, complex CuL2 exhibited highest α-amylase inhibitory activity with IC50 = 0.251 ± 0.2 mM and complex CuL1 exhibited highest α-glucosidase activity with IC50 = 0.060 ± 0.3 mM. In addition, compounds were also screened for their antimicrobial efficacy. All complexes were found significantly potent, among which complex CuL1 the most active with MIC of 15.3 µg/mL against S. aureus (MTCC 96).

Assessing the Ligand Properties of NHC-Stabilised Phosphorus(I) Cations.

The isolation and full characterisation of a series of cationic metal-carbonyl complexes bearing an N-heterocyclic carbene stabilised phosphorus(I) ligand are reported. Specifically, the mononuclear coordination complexes [LM(CO)5 ][BPh4 ] (M=Cr, Mo, W), [LFe(CO)4 ][BPh4 ] and the dinuclear complexes [LMn2 (CO)8 ][BPh4 ] and [LCo2 (CO)6 ][BPh4 ], in which L=[bis(1,3,4,5-tetramethylimidazol-2-ylidene)phosphanide]+ , have all been isolated in the solid state and structurally confirmed by single-crystal X-ray diffraction. The dicationic platinum complex trans-[L2 PtCl2 ][BPh4 ]2 is also reported and fully characterised. The donor ability of [L]+ has been assessed by IR spectroscopy of its metal-carbonyl complexes and by using DFT calculations. The results suggest that [L]+ is a weak π-acceptor with moderate donor strength and thus it bridges the gap that exists between phosphines and amines in terms of ligand properties. Collectively, these molecules represent the first crystallographically characterised cationic metal-carbonyl derivatives of a PI -centred ligand and are a rare collection of cationic metal-carbonyl complexes.

Syntheses and Crystal Structures of Quinidinum-Zinc(II)-Trichloride and Quinidinum Iron(III) Tetrachloride Hydrogen Chloride Hydrate

A mononuclear coordination complex, quinidinum-zinc(II)-trichloride (I), and a multi-component ionic complex, quinidinum iron(III) tetrachloride hydrogen chloride hydrate (II), have been synthesized and characterized by elemental analyses, IR spectra, and single crystal X-ray diffraction (CIF files nos. 1497628 (I) and 1497629 (II)). The weak hydrogen-bonding interactions exist in both complexes I and II. Both complexes crystallize in the chiral space groups with the absolute configuration. Complex I crystallizes in the orthorhombic space group P212121 with a = 7.6651(6), b = 11.4923(9), c = 24.653(2) A, and Z = 4. Complex II crystallizes in the monoclinic space group P21 with a = 6.6425(15), b = 18.660(4), c = 10.958(3) A, β = 104.973(3), and Z = 2.

Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O‐Donor Organic Ligand

AbstractWe have prepared and fully characterized two isomers of [IrIV(dpyp)2] (dpyp=meso‐2,4‐di(2‐pyridinyl)‐2,4‐pentanediolate). These complexes can cleanly oxidize to [IrV(dpyp)2]+, which to our knowledge represent the first mononuclear coordination complexes of IrV in an N,O‐donor environment. One isomer has been fully characterized in the IrV state, including by X‐ray crystallography, XPS, and DFT calculations, all of which confirm metal‐centered oxidation. The unprecedented stability of these IrV complexes is ascribed to the exceptional donor strength of the ligands, their resistance to oxidative degradation, and the presence of four highly donor alkoxide groups in a plane, which breaks the degeneracy of the d‐orbitals and favors oxidation.

Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O-Donor Organic Ligand.

We have prepared and fully characterized two isomers of [IrIV (dpyp)2 ] (dpyp=meso-2,4-di(2-pyridinyl)-2,4-pentanediolate). These complexes can cleanly oxidize to [IrV (dpyp)2 ]+ , which to our knowledge represent the first mononuclear coordination complexes of IrV in an N,O-donor environment. One isomer has been fully characterized in the IrV state, including by X-ray crystallography, XPS, and DFT calculations, all of which confirm metal-centered oxidation. The unprecedented stability of these IrV complexes is ascribed to the exceptional donor strength of the ligands, their resistance to oxidative degradation, and the presence of four highly donor alkoxide groups in a plane, which breaks the degeneracy of the d-orbitals and favors oxidation.

Dynamic in situ solvothermal reactions between ZnX2 (X = Cl, ClO4) and a heterocyclic disulfide

Solvothermal reactions of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide) with ZnX2 (X = Cl, ClO4) in mixed CH3OH–CH2Cl2 solvent have been investigated. To better understand these reactions, solution analysis was conducted in parallel with single-crystal X-ray diffraction analysis of the in situ generated coordination complexes. At 120 °C, solvothermal reaction of 2-ppds with ZnCl2 resulted in a discrete mononuclear coordination complex formulated as [ZnCl2(L1)] (1), in which the zwitterion L1 (1-methyl-4-(pyridin-2-yl)pyrimidin-1-ium-2-olate) was formed in situ from 2-ppds, and solution analyses based on TLC and ESI–MS further showed that the reaction solution also contains in situ transformed products of L2 (bis(4-(pyridin-2-yl)pyrimidin-2-yl)sulfane) and L3 (2-methoxy-4-(pyridin-2-yl)pyrimidine). At 90 °C, solvothermal reaction between 2-ppds and Zn(ClO4)2 led to a discrete mononuclear coordination complex formulated as [Zn(SH)(L2)]ClO4 (2) that features a terminally bound –SH group, while the reaction solution was also found to contain a library of in situ reaction products of 2-ppds including L1, L2, L3 and L4 ((4-(pyridin-2-yl)pyrimidin-2-yl) 4-(pyridin-2-yl)pyrimidine-2-sulfonothioate). Thus, the heterocyclic disulfide 2-ppds is transformed in situ into various organic products in a series of reactions involving C–S/S–S bond cleavage.

Synthesis, characterisation and catalytic activity of 4, 5-imidazoledicarboxylate ligated Co(II) and Cd(II) metal-organic coordination complexes

Two mono nuclear coordination complexes, namely, [Co(4,5-Imdc)2 (H2O)2] (1) and [Cd(4,5-Imdc)2(H2O)3]·H2O (2) were constructed using Co(II) and Cd(II) metal salts with 4,5-Imidazoledicarboxylic acid (4,5-Imdc) as organic ligand. Both 1, 2 were structurally characterized by single crystal XRD and the results reveal that 1 belongs to P21/n space group with unit cell parameters [a = 5.0514(3) Å, b = 22.5786(9) Å, c = 6.5377(3) Å, β = 111.5°] whereas, 2 belongs to P21/c space group with unit cell parameters [a = 6.9116(1) Å, b = 17.4579(2) Å, c = 13.8941(2) Å, β = 97.7°]. While Co(II) in 1 exhibited a six coordination geometry with 4,5-Imdc and water molecules, Cd(II) ion in 2 showed a seven coordination with the same ligand and solvent. In both 1 and 2, the hydrogen bond interactions with mononuclear unit generated 3D-supramolecular structures. Both complexes exhibit solid state fluorescent emission at room temperature. The efficacy of both the complexes as heterogeneous catalysts was examined in the green synthesis of six pyrano[2,3,c]pyrazole derivatives with ethanol as solvent via one-pot reaction between four components, a mixture of aromatic aldehyde, malononitrile, hydrazine hydrate and dimethyl acetylenedicarboxylate. Both 1 and 2 have produced pyrano [2,3,c]pyrazoles in impressive yields (92–98%) at room temperature in short interval of times (<20 min), with no need for any chromatographic separations. With good stability, ease of preparation and recovery plus reusability up to six cycles, both 1 and 2 prove to be excellent environmental friendly catalysts for the value-added organic transformations using green principles.

Synthesis, characterization, photoluminescence, and electrochemical studies of novel mononuclear Cu(II) and Zn(II) complexes with the 1-benzylimidazolium ligand

Two new mononuclear coordination complexes [Cu(bim)4Cl2]⋅2H2O (1) and [Zn(bim)2Cl2] (2) containing the 1-benzylimidazole (bim) ligand were successfully synthesized. Both complexes were characterized by IR, UV–vis, and fluorescence spectroscopies, single crystal and powder X-ray diffraction measurements, and thermogravimetric analysis. Self-assembly during the recrystallization process resulted in the formation of octahedral and tetrahedral Cu(II) and Zn(II) complexes, respectively. The single crystals obtained are representative of the bulk material, as shown by the powder X-ray diffraction patterns. Cyclic voltammetry measurements showed that complex 1 undergoes a quasi-reversible redox reaction, while complex 2 undergoes reduction alone, and no oxidation peak was observed; this is due to the stability of the reduced form of complex 2.

W(CO)3(Ph2PC2H4PPh2)(η(2)-Sc3N@Ih-C80/Sc3N@D5h-C80): regioselective synthesis and crystallographic characterization of air-stable mononuclear complexes of endohedral fullerenes.

The organometallic chemistry of endohedral metallofullerenes has lagged far behind that of empty fullerenes. Herein, we report a highly regioselective coordination reaction involving two Sc3N@C80 isomers and W(CO)4(Ph2PC2H4PPh2) (1), which affords only one mononuclear complex for each Sc3N@C80 isomer (2a for Sc3N@Ih-C80 and 2b for Sc3N@D5h-C80). X-ray results demonstrate that the tungsten center coordinates with the cages in an η(2) fashion on a [6,6]-bond in both cases, forming the first derivatives with a closed three membered ring for Sc3N@C80. Although IR and absorption spectroscopic results reveal relatively weak exohedral-metal to ligand π back-donation in both 2a and 2b, they show remarkable air-stability which promises their potential uses in related fields. Moreover, the coordination has narrowed down the electrochemical gaps of the parent Sc3N@C80 isomers, making the complexes better electron donors but worse electron acceptors than the corresponding precursors.