Single-crystal X-ray Structure Research Articles

Inelastic Neutron Scattering Measurement of the Ground State Tunneling Gap in Tb and Ho Analogues of a Dy Field-Induced Single-Molecule Magnet.

Recent advances in single-molecule magnet (SMM) research have placed great value on interpretation of inelastic neutron scattering (INS) data for rare earth (RE)-containing SMMs. Here, we present the synthesis of several rare earth complexes where combined magnetic and INS studies have been performed, supported by ab initio calculations. The reaction of rare earth nitrate salts with 2,2'-bipyridine (2,2'-bpy) and tetrahalocatecholate (X4Cat2-, X = Br, Cl) ligands in methanol (MeOH) afforded two new families of compounds [RE(2,2'-bpy)2(X4Cat)(X4CatH)(MeOH)] (X = Br and RE = Y, Eu, Gd, Tb, Dy, Ho, Yb for 1-RE; X = Cl and RE = Y, Tb, Dy, Ho, and Yb for 2-RE). Addition of triethylamine (Et3N) to the reaction mixture delivered Et3NH[RE(2,2'-bpy)2(Br4Cat)2] (3-RE, RE = Er and Yb). Interestingly, cerium behaves differently to the rest of the series, generating (2,2'-bpyH)2[Ce(Br4Cat)3(2,2'-bpy)] (4-Ce) with tetravalent Ce(IV) in contrast to the trivalent metal ions in 1-3. The static magnetic properties of 1-RE (RE = Gd, Tb, Dy and Ho) were investigated in conjunction with INS measurements on 1-Y, 1-Tb, and 1-Ho to probe their ground state properties and any crystal field excitations. To facilitate interpretation of the INS spectra and provide insight into the magnetic behavior, ab initio calculations were performed using the single-crystal X-ray diffraction structural data of 1-RE (RE = Tb, Dy and Ho). The ab initio calculations indicate ground doublets dominated by the maximal angular momentum projection states of Kramers type for 1-Dy and Ising type for 1-Tb and 1-Ho. Dynamic magnetic susceptibility measurements indicate that 1-Dy exhibits slow magnetic relaxation in the presence of a small applied magnetic field mainly through Raman pathways. Inelastic neutron scattering spectra exhibit distinct transitions corresponding to crystal field-induced tunneling gaps between the pseudo-doublet ground state components for 1-Tb and 1-Ho, which is one of the first direct experimental measurements with INS of such tunneling transitions in a molecular nanomagnet. The power of high-resolution INS is demonstrated with evidence of two distinct tunneling gaps measurable for the two crystallographically unique Tb coordination environments observed in the single crystal X-ray structure.

New N4-Donor Ligands as Supramolecular Guests for DNA and RNA: Synthesis, Structural Characterization, In Silico, Spectrophotometric and Antimicrobial Studies

The present work reports the synthesis of new N4-donor compounds carrying p-xylyl spacers in their structure. Different Schiff base aliphatic N-donors were obtained synthetically and subsequently evaluated for their ability to interact with two models of nucleic acids: calf-thymus DNA (CT-DNA) and the RNA from yeast Saccharomyces cerevisiae (herein simply indicated as RNA). In more detail, by condensing p-xylylenediamine and a series of aldehydes, we obtained the following Schiff base ligands: 2-thiazolecarboxaldehyde (L1), pyridine-2-carboxaldehyde (L2), 5-methylisoxazole-3-carboxaldehyde (L3), 1-methyl-2-imidazolecarboxaldehyde (L4), and quinoline-2-carboxaldehyde (L5). The structural characterisation of the ligands L1-L5 (X-ray, 1H NMR, 13C NMR, elemental analysis) and of the coordination polymers {[CuL1]PF6}n (herein referred to as Polymer1) and {[AgL1]BF4}n, (herein referred to as Polymer2, X-ray, 1H NMR, ESI-MS) is herein described in detail. The single crystal X-ray structures of complexes Polymer1 and Polymer2 were also investigated, leading to the description of one-dimensional coordination polymers. The spectroscopic and in silico evaluation of the most promising compounds as DNA and RNA binders, as well as the study of the influence of the 1D supramolecular polymers Polymer1 and Polymer2 on the proliferation of Escherichia coli bacteria, were performed in view of their nucleic acid-modulating and antimicrobial applications. Spectroscopic measurements (UV-Vis) combined with molecular docking calculations suggest that the thiazolecarboxaldehyde derivative L1 is able to bind CT-DNA with a mechanism different from intercalation involving the thiazole ring in the molecular recognition and shows a binding affinity with DNA higher than RNA. Finally, Polymer2 was shown to slow down the proliferation of bacteria much more effectively than the free Ag(I) salt.

1, 10-phenanthroline derivative as colorimetric and ratiometric fluorescence probe for Zn2+ and Cd2+

A colorimetric and ratiometric fluorescent probe 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (probe 1), was designed and synthesized for sensitive and selective detection of Zn2+ and Cd2+ ions in methanol, test paper and actual water samples. When probe 1 was excited at 350 nm in methanol solution, in the presence of alkali metal ions, alkali-earth metal ions and a variety of transition metal ions, it showed sensitive fluorescence selectivity to Zn2+ and Cd2+ ions. With the addition of Zn2+, the color of the solution changed from purple to cyan with the naked eye, and with the addition of Cd2+, the color of the solution changed from purple to blue. The fluorescence intensity of probe 1 showed a good linear relationship with Zn2+ and Cd2+ concentrations, and the detection limits were 0.04 μM and 0.11 μM, respectively. The binding mode of probe 1 and Cd2+ was discussed according to the 1-Cd single X-ray crystal structure. In addition, the results of strip test and real water sample test showed that probe 1 has potential application in environmental metal ion recognition and detection.

EXPLORATION OF COPPER-BASED COORDINATION POLYMER AS CATALYST: HIGH YIELD OXIDATIVE COUPLING OF BENZYLAMINE TO IMINE

Benzylamine to imine conversion through oxidative coupling reaction has been achieved with almost 91% yield under very mild conditions by applying a one-dimensional coordination polymer as a catalyst and tert-butyl hydroperoxide (TBHP) as an oxidizing agent. The 1D-coordination polymer, [{Cu2(2,3-pydc)2(2,2ʹ-bpy) (H2O)2}.4H2O]n(A) has been re-synthesized by different synthetic process using the ligands 2,3- pyridinedicarboxylic acid (2,3-pydc) and 2,2Ꞌ-bipyridine (2,2Ꞌ-bpy) and it has been characterized by utilizing different physicochemical techniques such as IR-spectroscopy, UV-Vis spectroscopy, elemental analysis and TGDTA analysis including reestablishment of X-ray single crystal structure. The proposed mechanism of the reaction indicates that the catalytic reaction is facilitated by a flexible and coordinatively unsaturated Cu(II) center and through the formation of tert-butyl peroxy radical.

Reactions of 4,5-difluoro-1,2-dinitrobenzene with amines in dimethylformamide or EtOH

Substitution reactions of 1,2-difluoro-4,5-dinitrobenzene were explored in dimethylformamide alone and with KOH/H2O, Hünig’s base or Et3N and with Me2NHCl/Et3N in EtOH. The fluorine atoms were always displaced in preference to the nitro groups. Three compounds were prepared from these studies and were characterised by X-ray single crystal structure determinations.

SYNTHESES AND CRYSTAL STRUCTURES OF COPPER(II) AND ZINC(II) COMPLEXES DERIVED FROM 5-BROMO-2-((CYCLOPROPYLIMINO)METHYL)PHENOL WITH ANTIBACTERIAL ACTIVITY

Four new complexes of copper(II) and zinc(II), [Cu2L4] (1), [Cu2L2(N(CN)2)2]n (2), [Zn(HL)2I2] (3) and [Zn(HL)2(NCS)2] (4), where L is 5-bromo-2-((cyclopropylimino)methyl)phenolate, HL is the zwitterionic form of 5-bromo-2-((cyclopropylimino)methyl)phenol, were synthesized and characterized by elemental analysis and IR and UV-Vis spectroscopy. Structures of the complexes were further confirmed by single crystal X-ray structure determination. Complex 1 is a phenolate bridged dinuclear copper(II) compound, with the Cu atom in square pyramidal coordination. Complex 2 is a phenolate and dicyanamide bridged polynuclear copper(II) compound, with the Cu atom in square pyramidal coordination. Complexes 3 and 4 are mononuclear zinc(II) compounds, with the Zn atoms in tetrahedral coordination. The compounds were assayed for their antimicrobial activities. Complexes 1 and 2 have the most activities on B. subtilis, with MIC values of 1.2 μg mL–1.

Ferrocenyl-based di- and trinuclear lanthanide complexes: solid state structures, (spectro)electrochemical and DFT studies.

Dinuclear and trinuclear ferrocenylcarboxylato-bridged lanthanide complexes of type [Ln(μO:κ2OO'-O2CFc)(O2CFc)2(H2O)(dmf)]2·(dmf)2 (Ln = Sm (2), Eu (3), Gd (4), Tb (5); Fc = Fe(η5-C5H4)(η5-C5H5)), and novel [Bu4N][Ln3(μ-O2CFc)3(μO:κ2OO'-O2CFc)3(O2CFc)3(μ3-OH)]·[Bu4N]Cl (Ln = Gd (6), Tb (7)) were prepared by the reaction of [LnCl3·6H2O] (synthesis of 2-5) or LnCl3 (synthesis of 6, 7) with FcCO2H (1) in the ratio of 1 : 3. As evidenced by single crystal X-ray structure determination, in 2-5 the lanthanide ions are connected by symmetric FcCO2 units. In addition, two ferrocenylcarboxylato groups are μ-bridged to LnIII. Each LnIII ion is coordinated by nine oxygen donor atoms derived from one H2O, one dmf and three carboxylates. The latter are found in chelating κ2 and bridging μ,κ3 coordination modes. Complexes 6 and 7 assemble three LnIII cores around a central μ3-netting hydroxide and nine FcCO2 entities. A combination of κ2, μ,κ2 and μ,κ3 coordination modes results in an eight-fold coordination sphere for each metal, which is best described as bicapped trigonal prismatic. IR spectroscopy confirms the chelating and bridging motifs. Electrochemical studies of complexes 2-7via cyclic voltammetry (CV) and square-wave voltammetry (SWV) showed one redox event between E°' = 250 and 260 mV vs. FcH/FcH+ for 2-5 with all six FcCO2 redox events superimposed. Complexes 6 and 7 show a total of three events in the CV with the oxidations of the nine FcCO2 units occurring in close proximity. Deconvolution of individual redox events correlates well with the mononuclear complex [Bu4N][Gd(O2CFc)4]. UV-Vis/NIR spectroelectrochemical measurements of 7 did not reveal electron transfer between either Fc units, nor the coordinated lanthanides and resembled the absorption behavior of [Bu4N][Tb(O2CFc)4]. DFT (Density Functional Theory) calculations on the B3LYP def2-TZVP level of theory were carried out to assign the order of redox events in 6 showing that the spatial distance towards the most recent redox center, instead of the binding mode, is decisive.

Mononuclear nickel(ii)-flavonolate complexes of tetradentate tripodal 4N ligands as structural and functional models for quercetin 2,4-dioxygenase: structures, spectra, redox and dioxygenase activity.

Three new nickel(ii)-flavonolate complexes of the type [Ni(L)(fla)](ClO4) 1-3, where L is the tripodal 4N ligand tris(pyrid-2-ylmethyl)amine (tpa, L1) or (pyrid-2-ylmethyl)bis(6-methylpyrid-2-ylmethyl)amine (6-Me2-tpa, L2) or tris(N-Et-benzimidazol-2-ylmethyl)amine (Et-ntb, L3), have been isolated as functional models for Ni(ii)-containing quercetin 2,4-dioxygenase. Single crystal X-ray structures of 1 and 3 reveal that Ni(ii) is involved in π-back bonding with flavonolate (fla-), as evident from enhancement in C[double bond, length as m-dash]O bond length upon coordination [H(fla), 1.232(3); 1, 1.245(7); 3, 1.262(8) Å]. More asymmetric chelation of fla- in 3 than in 1 [Δd = (Ni-Ocarbonyl - Ni-Oenolate): 1, 0.126; 3, 0.182 Å] corresponds to lower π-delocalization in 3 with electron-releasing N-Et substituent. The optimized structures of 1-3 and their geometrical isomers have been computed by DFT methods. The HOMO and LUMO, both localized on Ni(ii)-bound fla-, are highly conjugated bonding π- and antibonding π*-orbitals respectively. They are located higher in energy than the Ni(ii)-based MOs (HOMO-1, dx2-y2; HOMO-2/6, dz2), revealing that the Ni(ii)-bound fla- rather than Ni(ii) would undergo oxidation upon exposure to dioxygen. The results of computational studies, in combination with spectral and electrochemical studies, support the involvement of redox-inactive Ni(ii) in π-back bonding with fla-, tuning the π-delocalization in fla- and hence its activation. Upon exposure to dioxygen, all the flavonolate adducts in DMF solution decompose to produce CO and depside, which then is hydrolyzed to give the corresponding acids at 70 °C. The highest rate of dioxygenase reactivity of 3 (kO2: 3 (29.10 ± 0.16) > 1 (16.67 ± 0.70) > 2 (1.81 ± 0.04 × 10-1 M-1 s-1)), determined by monitoring the disappearance of the LMCT band in the range 440-450 nm, is ascribed to the electron-releasing N-Et substituent on bzim ring, which decreases the π-delocalization in fla- and enhances its activation.

Modulation of iron spin states in highly distorted iron(III) porphyrins: H-bonding interactions and implications in hemoproteins.

A family of five- and six-coordinated Fe-porphyrins which enable us to scrutinize the effects of non-covalent interactions on the out-of-plane displacement of iron and its spin-states and axial ligand orientation in a single distorted macrocyclic environment has been reported. Combined analysis using single-crystal X-ray structure determination and EPR spectral investigation revealed the stabilization of the high-spin state of iron in the five-coordinate complex FeIII(TPPBr8)(OCHMe2), while six-coordinate complexes [FeIII(TPPBr8)(MeOH)2]ClO4, [FeIII(TPPBr8)(H2O)2]ClO4 and [FeIII(TPPBr8)(1-MeIm)2]ClO4 stabilize admixed-high, admixed-intermediate and low-spin states, respectively. The H-bonding interactions between the weak axial H2O/MeOH and perchlorate anion resulted in an elongation of the Fe-O bond which eventually shortened the Fe-N(por) distances leading to the stabilization of the admixed spin state of iron which, otherwise, stabilizes the high-spin (S = 5/2) state only. In addition, the iron atom in [FeIII(TPPBr8)(H2O)2]ClO4 is displaced by 0.02 Å towards one of the water molecules engaged in the H-bonding interactions leading to two different Fe-O (H2O) distances of 2.098(8) and 2.122(9) Å. In contrast, iron in [FeIII(TPPBr8)(MeOH)2]ClO4 sits on the plane of the porphyrin since both the axial methanol units are engaged in similar H-bonding interactions with the ClO4- ion. Moreover, the X-ray structure of low-spin FeII(TPPBr8)(1-MeIm)2 revealed a dihedral angle of 63.0° between two imidazoles which deviates largely from the expected angle of 90° (perpendicular orientations) since the axial imidazole protons are engaged in strong intermolecular C-H⋯π interactions which thereby restrict the axial ligand movement. The complex also displays the shortest Fe-N(1-MeIm) bond along with smallest dihedral angles of 7.8° and 22.4° between the axial imidazole ring and the closest Fe-Np axis due to strong π-interactions between iron and the axial imidazole ligand. Our work highlights the influence of non-covalent interactions on the out-of-plane displacement and spin state of iron and axial ligand orientations which are indeed important steps in the functioning of various hemoproteins.

Chlorinated polyhedral selenaboranes revisited by joint experimental/computational efforts: the formation of closo-1-SeB9Cl9 and the crystal structure of closo-SeB11Cl11.

The recent success in the formation of chlorinated telluraboranes and the reactivities of pnictogenaboranes prompted us to re-examine the vacuum co-pyrolysis of B2Cl4 with Se2Cl2 at various molar ratios and temperatures in order to search for the generation of other polyhedral selenaboranes than closo-SeB5Cl5 (1a) and closo-SeB11Cl11 (1b), the latter being observed earlier. Interestingly, a new compound with the elemental composition SeB9Cl9 (2) was detected, this time by high- and low-resolution mass spectrometry. Further characterization by 1- and 2-D 11B-NMR spectroscopy suggests that 2 should adopt a closed bicapped square-antiprismatic geometry with selenium at the apical position. Moreover, vacuum sublimation gave suitable crystals of 1b, which were subjected to single-crystal X-ray structure determination. Crystallographic data analysis confirmed that 1b, consistent with its 26 skeletal electron count, adopts a distorted icosahedral structure close to the symmetry of C5v. Computations at the DFT-D3 level have revealed that 33% of the total computed binding motifs in the grown 1b crystals are due to the very strong chalcogen bonding. Moreover, SAPT decomposition has shown that the bonding motifs in the crystals are stabilized mainly by dispersion and electrostatic terms. Homodecoupling and high resolution 11B NMR and 77Se NMR experiments have resolved both coupling constants 1J(11B11B) and 1J(77Se11B) as well as the 77Se chemical shift of 1a and 1b, which are in reasonable agreement with the corresponding computed values. The computed 11B chemical shifts of 2 were determined by the well-established DFT/GIAO/NMR structural tool based on its B3LYP/6-311+G** internal coordinates. They agree well with the experimental values and provide a good representation of the molecular structure of 2 in solution. The extraordinary downfield 11B NMR chemical shift of B(10) in 2 has been ascribed to the intensive paramagnetic contribution to the shielding tensor in this bicapped square-antiprismatic motif. Calculations of the synproportionation free energies of smaller (n - 1) closo-selenaboranes with larger-sized (n + 1) ones support the extraordinary stability of octahedral, bicapped square-antiprismatic and icosahedral closo motifs in the SeBnCln family (n = 4-12).

The crystal magnification, characterization, X-ray single crystal structure, thermal behavior, and computational studies of the 2,4,6-trimethylpyridinium picrate

A crystal of organic salt, 2,4,6-trimethylpyridinium picrate (TMPPc), was synthesized and magnified by slow evaporation in a polar aprotic solvent and characterized by 1H NMR, 13C NMR, and FT-IR spectroscopic methods. X-ray diffraction analysis of the crystal structure of the compound TMPPc showed the presence of a monoclinic space group with a = 4.0174(4) Å, b = 27.863(3) Å, c = 13.9247(17) Å, β = 95.741(4)°, V = 1550.9(3) Å3, Z = 4, T = 296 K, μ(MoKα) = 0.123 mm-1, Dcalc = 1.500 g/cm3, 62749 reflections measured (5.88° ≤ 2Θ ≤ 57.058°), 3911 unique (Rint = 0.0536, Rsigma = 0.0226) which were used in all calculations. The final R1 was 0.0569 (I > 2σ(I)) and wR2 was 0.1710 (all data). Detailed investigation of molecular packing of the TMPPc molecule indicated the presence of intermolecular hydrogen bond between N4-H44···O1 and C13-H13B···O4 that generates C22(14) chain running parallel to the [001] direction. The infrared and Raman spectra of the prepared TMPPc compound were recorded and discussed. The thermal stability of the obtained TMPPc crystal was analysed by TGA/DTG technique and revealed that the crystal was stable up to 162 °C. Density functional theory calculations such as the value of the HOMO and LUMO energy gap, the parameters of the molecular electrostatic potential, the global reactivity and thermodynamic properties of the compound TMPPc were also performed using the DFT/B3LYP method with the level of the 6-311G (d, p) basis set.

β-Functionalized palladium(II) porphyrins: Facile synthesis, structural, spectral, and electrochemical redox properties

Two [Formula: see text]-substituted Pd(II) porphyrins, (PdTPP(NO[Formula: see text]Ph2 and PdTPP(Ph)[Formula: see text], were synthesized and characterized by various spectroscopic techniques, and their spectral and electrochemical redox properties were investigated with respect to PdTPP. The single-crystal X-ray structure of PdTPP(NO[Formula: see text]-Ph2 revealed saddle-shape conformation of the macrocyclic core of porphyrin. DFT studies revealed nonplanar saddle shape conformation of PdTPP(Ph)4 with an average deviation of [Formula: see text]-pyrrole carbon atoms from the porphyrin mean plane ([Formula: see text]C[Formula: see text] = ± 0.751 Å) and also 24 core atoms ([Formula: see text]24 = ± 0.368 Å) as compared to PdTPP(NO[Formula: see text]Ph2 ([Formula: see text]C[Formula: see text] = 0.649 Å and [Formula: see text]24 = ± 0.317 Å) due to more [Formula: see text]-pyrrole substitution. Both PdTPP(NO[Formula: see text]Ph2 and PdTPP(Ph)4 exhibited 13-19 nm and 49-59 nm red-shift in the Soret and Q[Formula: see text] bands as compared to PdTPP, respectively. PdTPP(NO[Formula: see text]Ph2 exhibited a very high dipole moment (7.32 D) as compared to PdTPP(Ph)4 (0.239 D) due to the “push-pull” effect of electron donor (phenyl) and acceptor (-NO[Formula: see text] groups at the [Formula: see text]-pyrrole positions of the macrocycle. The redox potentials of PdTPP(NO[Formula: see text]Ph2 anodically shifted ([Formula: see text]E = 0.2-0.4V) as compared to PdTPP and PdTPP(Ph)4 due to the presence of [Formula: see text]-phenyl groups and the strong electron-withdrawing effect of the nitro group. Hence the HOMO-LUMO energy gap of PdTPP(NO[Formula: see text]Ph2 decreased by 0.20 V and 0.28 V as compared to PdTPP(Ph)4 and PdTPP, respectively.

Characterization of the O-centered vanadium selenoiodides V4OSe8I6·X (X = I2, 3,5-dimethylpyrazole)

O-centered vanadium(IV) selenoiodide V4OSe8I6·3,5-dimethylpyrazole was synthesized in a sealed glass ampoule at moderate temperature 220 °C from the mixture of V, Se, I2, small quantity of water and 3,5-dimethylpyrazole. The X-ray single crystal structure of the compound was solved. The crystal structure includes O-centered tetranuclear complex [V4(μ4-O)(μ-Se2)4(μ-I)2I4] in which vanadium atoms are bridged by diselenide (Se2)2– and iodide I– groups; four terminal iodides coordinate vanadium atoms additionally. Molecules of 3,5-dimethylpyrazole form non-covalent contacts with iodine and selenium atoms of the V4OSe8I6 complexes. Once compounds V4OSe8I6·3,5-dimethylpyrazole and V4OSe8I6·I2 contain similar electroneutral coordination molecular fragment V4OSe8I6, we present here a discussion of spectroscopic properties as well as thermal behavior. Comparing XPS data, both compounds contain vanadium complexes with major V 2p binding energies very similar to each other, and almost equal binding energies in XPS Se 3d and I 3d showing their forms of (Se2–)2 and I–, respectively. Thermolysis character of these compounds revealed higher stability of V4OSe8I6·I2 than V4OSe8I6·3,5-dimethylpyrazole, that indicates a greater stability of the system of non-covalent contacts involving iodine molecules than 3,5-dimethylpyrazole.

Unprecedented formation of azulicorroles from the scrambling of azulitripyrrane

In this study, we have prepared new tripyrranes embedded with azulene bearing two meso-pentafluorophenyl substituents. They were obtained as diastereomers in high yield which were separated using conventional column chromatography. Their distinct solution structures were unambiguously confirmed by NMR and mass analysis. Our synthetic strategy is simple and straightforward due to the reactivity of 1,3-positions of azulene, which underwent Lewis acid-catalyzed condensation with pyrrole-2-carbinol. These diastereomers were further subjected to acid-catalyzed (CF3COOH) condensation with pyrrole dicarbinol to afford the target N-confused azuliporphyrin (reduced form) in trace amount. However, we obtained the tris-meso-pentafluorophenyl substituted azulicorrole (AzCorA) as major product due to an unprecedented scrambling of the azulitripyrranes. The structural characterization of newly synthesized key precursors and macrocycles was done with the aid of high-resolution mass analyses, and 1H and 2D NMR analyses. The single crystal X-ray structure obtained for AzCorArevealed that the azulene subunit is tilted by 34.03[Formula: see text] due to the steric congestion of inner-NHs.

Synthesis, structure, thermal and magnetic properties of new tetranuclear copper(II) complex supported by multidentate ligand and glutarate functionality

A new tetranuclear Cu(II) complex, [Cu(H2O)4][Cu4(cpdp)2(glut)]Cl2·6H2O (1) was successfully constructed by utilization of carboxylate-based multidentate ligand N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H3cpdp), in combination with glutarate (glut) and Cu(II) ions, and characterized systematically. Originally, the symmetrical flexible ligand cpdp3− is capable to bind two Cu(II) ions, leaving behind accessible binding sites for further coordination of exogenous glutarate anion which facilitates the assembly of two ligand-bound Cu(II) pairs. In MeOH/H2O, the reaction of CuCl2·2H2O with H3cpdp and sodium glutarate in the presence of NaOH results in the formation of 1. Complex 1 was characterized by different analytical techniques, including single crystal X-ray structure investigation. Analysis of single crystal X-ray structure shows that 1 is a self-assembled tetranuclear copper complex in which two dinuclear [Cu2(cpdp)]+ species are exclusively bridged by one glutarate functionality through μ4:η1:η1:η1:η1 manner, acting as a coligand. Thermoanalytical methods (TGA/DTA) were used to examine the thermal stability and it was observed that 1 is stable up to ∼190°C. Variable temperature (2-300 K) magnetic susceptibility studies show the weak antiferromagnetic interactions among the copper centers with the value of magnetic exchange coupling constant (J) of -0.5 cm−1.

One pot synthesis of two potent Ag(I) complexes with quinoxaline ligand, X-ray structure, Hirshfeld analysis, antimicrobial, and antitumor investigations

In one pot, the self-assembly of AgNO3 and 2-chloroquinoxaline (2Cl-quinox) in water–ethanol mixture afforded two novel crystalline Ag(I) complexes. The major product is the polymeric complex [Ag(2Cl-quinox)(NO3)]n; (1), while the minor product (2) comprises two molecules which are the monomeric [Ag(2Cl-quinox)2(NO3)]; (2a) and polymeric [Ag(2Cl-quinox)(NO3)]n; (2b) complexes. The single crystal X-ray structure revealed that 1 and 2b are made up of two-dimensional infinite sheets. In contrast, 2a is a monomeric complex which has a highly distorted tetrahedral geometry around Ag(I) center. In all cases, the 2Cl-quinox molecule acts as a terminal monodentate ligand. Complexes 1 and 2b have similar molecular structures and also have almost similar crystal packing. Using Hirshfeld surface analysis, the O…H hydrogen bonds and π–π stacking interactions contributed significantly to the molecular packing. Both complexes have broad-spectrum action towards multi drug-resistance bacteria. The most effective function of 2 is against Proteus morganii, with a MIC value of 8 μg/mL. Complex 2 (IC50 = 5.93 ± 0.52 μg/mL) has remarkably greater cytotoxic effect against lung carcinoma (A-549) than cis-platin (IC50 = 7.5 ± 0.69 μg/mL) and AgNO3 (IC50 = 14.7 ± 0.53 μg/mL). The higher Ag-content in 2 could be the main reason for its higher cytotoxicity than 1.

Phenanthroline-based ligand scaffold as an efficient colorimetric and ratiometric fluorescence probe for Zn2+ and Cd2+ ion detection

A colorimetric and ratiometric fluorescent probe 2-(naphthalen-2-yl)-2,11b-dihydro-1H-imidazo[4,5-f][1,10]phenanthroline (probe 1), was designed and synthesized for sensitive and selective detection of Zn2+ and Cd2+ in methanol, test paper and actual water samples. When probe 1 was excited at 350 nm in methanol solution, in the presence of alkali metal ions, alkali-earth metal ions and a variety of transition metal ions, it showed sensitive fluorescence selectivity to Zn2+ and Cd2+. With the addition of Zn2+, the color of the solution changed from purple to green with the naked eye, and with the addition of Cd2+, the color of the solution changed from purple to cyan. The fluorescence intensity of probe 1 showed a good linear relationship with Zn2+ and Cd2+ concentrations, and the detection limits were 0.09 μM and 0.06 μM, respectively. The binding mode of probe 1 and Zn2+ was discussed according to the 1-Zn single X-ray crystal structure. In addition, the results of strip test and real water sample test showed that probe 1 has potential application in environmental metal ion recognition and detection.

Synthesis, characterization and cytotoxicity of copper (II) complex containing a 2H-benzo[e][1,3]oxazin derivative

A new cis-dihalo copper(II) complex, [CuII(HLbz)(Cl)2].CH3CN (1), where HLbz = (S)-2-(((2-(2-(pyridin-2-yl)-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethyl)amino)methyl)phenol), was isolated by reacting copper(II) chloride dihydrate and the H2L ligand (H2L = 2,2′-((2-(pyridin-2-yl)imidazolidine-1,3-diyl)bis(methylene))diphenol) in a MeOH/CH3CN (1:3 v/v) mixture. The complex formation occurred via the ligand modification during complexation, producing a unique structure containing 2H-benzo[e][1,3]oxazin, as observed from the single crystal X-ray structure determination. The complex was characterized by elemental analysis, potentiometric titration, spectroscopic techniques (UV–Vis, FT-IR) and conductance measurements. Complex 1 inhibits the growth of myelogenous leukemia cells with an IC50 of 17.3 μmol L−1.

Synthesis, crystal structure and biological properties of a fluorophore-labelled mixed-ligand copper(II) complex incorporating N-hydroxynaphthalene-1,8-dicarboximide.

The mixed-ligand fluorophore-labelled copper(II) complex aqua[2,4-dioxo-3-azatricyclo[7.3.1.05,13]trideca-1(12),5,7,9(13),10-pentaen-3-olato-κ2O2,O3](1,10-phenanthroline-κ2N,N')copper(II) nitrate, [Cu(C12H6NO3)(C12H8N2)(H2O)]NO3·CH3OH or [Cu(L)(phen)(H2O)]NO3·CH3OH (where phen is 1,10-phenanthroline and HL is N-hydroxynaphthalene-1,8-dicarboximide), (1), was synthesized and structurally characterized. The structure of (1) was confirmed by single-crystal X-ray structure determination. The complex crystallized in the triclinic space group P-1. The geometry around the copper centre is distorted square pyramidal, with the apical position occupied by a water molecule. The complex is highly fluorescent in organic and aqueous solutions. It has good anticancer activity, with an IC50 value of 17 µM, which is almost five times greater than cisplatin (IC50= 82 µM) under identical experimental conditions.

Open-Cage Fullerene as Molecular Container for F- , Cl- , Br- and I.

A 19-membered open-cage fullerene derivative was prepared from C60 in 7 steps and 5.5 % yield through the peroxide-mediate pathway. There are four carbonyl groups, an ether oxygen and a quinoxaline moiety on the rim of the orifice. A chloride anion could be inserted into its cavity by heating with hydrochloric acid at 60 °C for 4 h. Encapsulation of fluoride, bromide and iodide anions was also achieved at slightly more forcing conditions, 90 °C for 14 h. Single crystal X-ray structures of the sodium salt of the chloride and the bromide encapsulated derivatives were obtained, which showed the halide anion in the center of the cavity and two sodium cations connecting two cages through coordination to the oxygen atoms on the rim of the orifices. The halide encapsulation ratio is quantitative in the isolated products.