CuN4 Chromophore Research Articles

Copper(II)-Nickel(II) Induced Cyanide Bridged 2D Heterometallic Coordination Polymer: Synthesis, X-ray Structure and Magnetic Study

One new two-dimensional heterometallic coordination polymer [Cu3Ni(L)2(CN)6]n (1) [L = 2-methylethylenediamine, CN– = cyanide ion] was synthesized and characterized by X-ray crystallography. Compound 1 crystallizes in the monoclinic C2/c space group. The single crystal X-ray structure of compound 1 indicated that it is a 2D coordination polymer with three copper(II) ion embedded with [Ni(CN)4]2- molecular ion in architecture through μ-CN/μ-NC bridges results heterometallic polymer. In compound 1, each Cu1 center with a CuN5 chromophore is encompassed by four N atoms of the two different bidentate amine (L) and one N atom of μ-NC ion, while both Cu2 and Cu3 centres are connected by three N atoms of μ-NC ions having CuN3 chromosphere and Ni1 are coordinated by three μ-CN and one terminal CN ions with NiC4 chromophore. Three copper centers and one nickel center are interlinked through μ-CN/μ-NC forming {-Cu1(L)2(μ-NC)Ni1(CN)(μ-CN)2Cu2(μ- NC)Cu3(μ-NC)-} unit to fabricate a 2D hetero metallic polymer. In the crystalline state of compound 1, each 2D polymer is further propagated through intermolecular N-H···N hydrogen bonds corroborant a supramolecular 2D network structure. Variable temperature magnetic susceptibility study displayed a weak antiferromagnetic spin coupling presumably due to the diamagnetic tetracyanonickellate bridging among the CuII ions.

Cyanide bridged 2-D homometallic mixed-valence copper coordination polymer: synthesis, crystal architecture, Hirshfeld surface analysis and magnetic behavior

A 2-D homometallic mixed-valence copper coordination polymer, catena-poly[[tetrakis(μ-cyanido)-{(1-(N-acetopyridinine)-2-aminoethane)}-tri-copper] methanol monosolvate], {[Cu3(L)(CN)4]·CH3OH}n (1) [L = 1-(N-acetopyridinine)-2-aminoethane], has been isolated using a one-pot reaction of the building components and was characterized. The crystal structure consists of [CuIIL]2+ units and copper(I) ions bridged by μ-CN anions. The copper(II) center of the CuN5 chromophore displays a square pyramidal coordination geometry provided by three N atoms of the tridentate Schiff base and two N atoms of μ-NC ions, while the copper(I) centers adopt a trigonal-planar geometry. Three copper centers are interconnected through μ-CN/μ-NC via {-Cu1(L)(μ-NC)2Cu2(μ-CN)Cu3(μ-NC)-} units to form 2-D polymeric ribbons parallel to the b-axis. These 2-D polymeric ribbons in the crystalline state are further stabilized through π···π stacking interactions. Hirshfeld surface analysis was performed to gain additional insight into the interactions responsible for the packing of 1. Variable-temperature magnetic susceptibility studies showed a weak ferromagnetic interaction among the copper centers in 1 through cyanide bridges with J = 1.28 cm−1.

Azido derivatives of dinuclear copper(II) and 1D polynuclear nickel(II) complexes containing an unsymmetrical bidentate amine: synthesis, crystalline architecture, and magnetic behavior

Dinuclear copper(II) complex [Cu2(L)2(μ2-1,1-N3)2(N3)2] (1) with double μ1,1-azido bridges and polynuclear nickel(II) complex [Ni(L)(μ2-1,1-N3)(μ2-1,3-N3)]n (2) with alternate double μ1,1-azido and μ1,3-azido bridges [L = 1-amino-2-(dimethylamino)ethane, N 3 − = azide ion] have been synthesized and were characterized by physicochemical and spectroscopic methods. X-ray structural analysis revealed that each Cu(II) center of 1 adopts a distorted square-pyramidal geometry with a CuN5 chromophore ligated through two N atoms of L, two N atoms of double bridging (μ1,1-N3), and one N atom of terminal azide ion. On the other hand, each Ni(II) center around the asymmetric unit of 2 adopts a distorted octahedral geometry with a NiN6 chromophore ligated through two N atoms of L, two N atoms of double μ1,1-N3, and two N atoms of double μ1,3-N3 bridges. The adjacent nickel centers are connected to alternate double μ1,1-N3 and double μ1,3-N3 bridges, affording a one-dimensional (1D) polymeric chain structure. Temperature-dependent magnetic susceptibility measurements evidenced a dominant antiferromagnetic interaction between the metal centers of both complexes 1 and 2.

Syntheses, structures and magnetic behaviors of 1D and 3D µ1,5-dicyanamide bridged copper(II) coordination polymers containing a symmetrical 1,2-diamine as a chelator

Two neutral copper(II) coordination polymers, [Cu(en)(µ1,5-dca)(dca)]n (1) and [Cu3(en)2(µ1,5-dca)6]n (2) [en = 1,2-ethanediamine, dca = dicyanamide], with µ1,5-dicyanamide bridges have been isolated. X-ray structural analysis reveals that each Cu(II) center in the asymmetric unit of 1 adopts a distorted square pyramidal geometry with a CuN5 chromophore ligated through two N atoms of the symmetrical 1,2-ethanediamine (en) ligand, one nitrile N atom of a terminal dca ligand and two nitrile N atoms of the μ1,5 bridging dca ligand. 1 is an example of coordination polymer containing both μ1,5-dca and terminal dca. Adjacent copper atoms are connected by dca ligands in the μ1,5-bridging mode affording a 1D chain structure. In the crystalline state, these 1D chains are further associated through weak intermolecular NH⋯N hydrogen bonds to form a 2D sheet structure, viewed along the crystallographic b axis. The asymmetric unit of 2 contains two types of copper(II) centers (Cu1 and Cu2). Cu1 adopts a distorted square pyramidal geometry with a CuN5 chromophore coordinated through two N atoms of the bidentate ligand (en) and three nitrile N atoms of three different μ1,5 bridged dca ligands, whereas Cu2 is connected to six nitrile atoms of six different μ1,5 bridged dca ligands, resulting in a distorted octahedral geometry with a CuN6 chromophore. Adjacent copper atoms are connected by μ1,5-bridging dca ligands to form a 3D network coordination polymer structure, which contains multiple NH∙∙∙N hydrogen bonds in the crystalline state. A variable-temperature magnetic susceptibility study shows very weak antiferromagnetic interactions among the neighboring metal centers through the μ1,5-dca bridges with J = −0.12 cm−1 for complex 1 and J = −0.19 cm−1 for complex 2.

DNA and BSA Interaction, DNA Cleavage and <i>In Vitro</i> Cytotoxicity of Copper(II) Complexes: [Cu(bba)(phen)](ClO<sub>4</sub>)<sub>2</sub> is Promising Chemotherapeutic Scaffold

Three mononuclear copper(II) complexes of the type [Cu(bba)(bpy/phen/dpa)](ClO4)2 (1-3), where bba (N,N-bis(benzimidazol-2-ylmethyl)amine) and bpy (2,2’-bipyridine, 1) or phen (1,10-phenanthroline, 2) or dpa (2,2’-dipyridylamine, 3), have been isolated. The coordination geometry of 1 around copper(II) is square pyramidal. The electronic absorption (639-667 nm) and EPR spectral parameters (g||, ~2.25; A||, 181-186 × 10-4 cm-1; g||/A||, 122−134 cm) reveal that 1-3 possesses a square pyramidal geometry with CuN5 chromophore. Different spectral and electrochemical measurements clearly demonstrate partial intercalative interaction of 1-3 to CT DNA. Complexes strongly quench the intrinsic fluorescence of BSA through a static quenching procedure by forming BSA-(1/2/3) adducts, which are stabilized by hydrophobic interactions. The number of binding sites and binding constants were calculated. The energy transfer from BSA to Cu(II) complexes occurs with high probability. Notably, 1-3 exhibit more effective pUC 19 DNA cleavage in the presence of H2O2. Complexes 2 and 1 show remarkable cytotoxicity (IC50: 2, 2.17; 1, 8.33 mM) against human cervical carcinoma cells (HeLa) and more potent than cisplatin (IC50, 16.40 mM) while 3 exhibits less cytotoxicity (IC50, 20.82 mM). The DNA binding propensity, cleavage ability and cytotoxicity follow the order 2>1>3. Interestingly, they are non-toxic to healthy cells.

Synthesis, crystal structure, DNA cleavage and antitumor activity of two copper(II) complexes with N-sulfonamide ligand

Two Cu(II) complexes, [Cu(L1)2(py)2(H2O] (C1) (HL1 = N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)-naphtalenesulfonamide) and [Cu(HL2)4](OH)2 (C2) (HL2 = N-(5-(4-methoxyphenyl)-[1,3,4]-thiadiazole-2-yl)-toluenesulfonamide) with two new obtained ligands were synthesized. The X-ray crystal structures of the complexes have been determined. In the complex C1, the Cu(II) ion is five-coordinated, forming a CuN4O chromophore and in the complex C2, the Cu(II) ion is four-coordinated, forming a CuN4 chromophore. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom. For the complex C1, the molecules from the reaction medium (pyridine and water) are also involved in the coordination of the Cu(II) ion. The complexes have a slightly distorted square pyramidal square-planar (C1) and a square-planar (C2) geometry. The compounds were characterized by FT-IR, electronic, EPR spectroscopic and magnetic methods. The nuclease activity studies of the synthesized complexes confirm their capacity to cleavage the DNA molecule. The results of in vitro cell cytotoxicity on three carcinoma cell lines (HeLa, A2780 and A2780cisR) are in concordance with the DNA cleavage study and with the SOD-mimetic activity and indicate that both complexes have antitumor activity. The antitumor activity was compared with Cisplatin and C1 complex demonstrated a higher activity. Both complexes overcame the Cisplatin resistance tence in A2789cisR cells whitout enhanced toxicity on normal fibroblastic cells.

Synthesis, Crystal Structures and Characterization of a New Antitumor Cu(II) Complex with N-sulfonamide Ligand

A new Cu(II) complex with N-sulfonamide ligand, [Cu(N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)-toluenesulfonamidate)4]((CH3)2NH2+)2(complex) has been synthesized and characterized. The X-ray crystal structure of the complex has been determined. The Cu(II) ion is four-coordinated, forming a CuN4 chromophore. The ligand acts as monodentate, coordinating the metal ion through a single Nthiadiazole atom. The complex has a square planar geometry. The characterization of the complex has been studied by FT-IR, electronic, EPR spectroscopic and magnetic methods.

Synthesis, crystal structures, characterization and antitumor activities of two copper(II) complexes of a sulfonamide ligand

An N-sulfonamide (HL = N-(5-(4-methoxyph-enyl)-[1, 3, 4]–thiadiazole–2-yl)-naphtalenesulfonamide) and two of its Cu(II) complexes, [Cu(L)2(py)2] (C1) and [Cu(L)(phen)2](L)1.25(MeOH) (C2), were synthesized. The X-ray crystal structures of the complexes have been determined. In complex C1, the copper atom is four-coordinated, forming a CuN4 chromophore, while in complex C2, the copper atom is five-coordinated, forming a CuN5 chromophore. The ligand acts as monodentate, coordinating the metal through a single thiadiazole N atom. The molecules from the reaction medium (pyridine and phenanthroline) are also involved in coordination to the copper atoms. The complexes have a square planar (C1) and slightly distorted square pyramidal (C2) geometries. The compounds were characterized by physicochemical and spectroscopic methods. Nuclease activity studies of the complexes confirm their capacity to cleave DNA. Both complexes also have SOD-like activity, but weaker than the native Cu2Zn2SOD activity. Cytotoxicity studies were carried out on melanoma cell line B16F10 and on normal retinal epithelial cell line (D407) and confirmed that C2 inhibits the growth of B16F10 cells, in a dose-dependent manner. Also, C2 displays a cytoselective profile, since it is not toxic to the D407 cell line. The results of the cell cytotoxicity studies are in concordance with the DNA cleavage and SOD mimetic activity studies and indicate that complex C2 has a high biological activity.

Influence of the N-terminus acetylation of Semax, a synthetic analog of ACTH(4-10), on copper(II) and zinc(II) coordination and biological properties

Semax is a heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) that encompasses the sequence 4-7 of N-terminal domain of the adrenocorticotropic hormone and a C-terminal Pro-Gly-Pro tripeptide. N-terminal amino group acetylation (Ac-Semax) modulates the chemical and biological properties of parental peptide, modifying the ability of Semax to form complex species with Cu(II) ion. At physiological pH, the main complex species formed by Ac-Semax, [CuLH−2]2−, consists in a distorted CuN3O chromophore with a weak apical interaction of the methionine sulphur. Such a complex differs from the Cu(II)-Semax complex system, which exhibits a CuN4 chromophore. The reduced ligand field affects the [CuLH−2]2− formal redox potential, which is more positive than that of Cu(II)-Semax corresponding species.In the amino-free form, the resulting complex species is redox-stable and unreactive against ascorbic acid, unlike the acetylated form. Semax acetylation did not protect from Cu(II) induced toxicity on a SH-SY5Y neuroblastoma cell line, thus demonstrating the crucial role played by the free NH2 terminus in the cell protection. Since several brain diseases are associated either to Cu(II) or Zn(II) dyshomeostasis, here we characterized also the complex species formed by Zn(II) with Semax and Ac-Semax. Both peptides were able to form Zn(II) complex species with comparable strength. Confocal microscopy imaging confirmed that peptide group acetylation does not affect the Zn(II) influx in neuroblastoma cells. Moreover, a punctuate distribution of Zn(II) within the cells suggests a preferred subcellular localization that might explain the zinc toxic effect. A future perspective can be the use of Ac-Semax as ionophore in antibody drug conjugates to produce a dysmetallostasis in tumor cells.

Crystal structure and antimicrobial properties of a copper(II) complex with 1,10-phenanthroline and azide co-ligand

ABSTRACT A novel Cu(II) complex with mixed ligands, [azido-bis(1,10-phenanthroline-κ2N,N′)copper(II)]nitrate hydrate has been synthesized and was characterized by physicochemical and spectroscopic methods. The central Cu(II) atom is five coordinate with four N atoms of two 1,10-phenanthroline molecules and one terminal N atom from an azide anion, giving a distorted trigonal bipyramidal geometry with a CuN5 chromophore. The molecular structure of the compound is consolidated by H-bonding and face-to face π-π stacking between the aromatic rings of 1,10-phenanthroline ligand. The ligands, metal salt, and the complex were also evaluated for their antimicrobial activities in vitro.

Synthesis, crystal structure and characterization of new biologically active Cu(II) complexes with ligand derived from N-substituted sulfonamide

A new N-sulfonamide ligand (HL1 = N-(5-(4-methoxyphenyl)-[1,3,4]–thiadiazole–2-yl)-toluenesulfonamide) and two Cu(II) complexes, [Cu(L1)2(py)2] (C1) and [Cu(L2)2(py)2(H2O)] (C2) (HL2 = N-(5-(4-methylphenyl)-[1,3,4]–thiadiazole–2-yl)-benzenesulfonamide) were synthesized. The X-ray crystal structures of the complexes were determined. In the complex C1, the Cu(II) ion is four-coordinated, forming a CuN4 chromophore and in the complex C2, the Cu(II) ion is five-coordinated, forming a CuN4O chromophore. The ligand acts as monodentate, coordinating the Cu(II) ion through a single Nthiadiazole atom. The molecules from the reaction medium (pyridine and water) are also involved in the coordination of the Cu(II) ion. The complexes C1 and C2 are square-planar and a slightly distorted square pyramidal, respectively. The compounds were characterized by FT-IR, electronic, EPR spectroscopic and magnetic methods. The nuclease binding activity studies of the synthesized complexes confirm their capacity to cleave the DNA molecule. The cytotoxicity studies were carried out on melanoma cell line WM35 which confirm that both compounds inhibit the growth of these cells. They have a higher activity compared to a platinum drug, carboplatin. A new N-sulfonamide ligand (HL1= N-(5-(4-methoxyphenyl)-[1,3,4]–thiadiazole–2-yl)-toluenesulfonamide) and two Cu(II) complexes, [Cu(L1) 2 (py) 2 ] and [Cu(L2) 2 (py) 2 (H 2 O)] (HL2= N-(5-(4-methylphenyl)-[1,3,4]–thiadiazole–2-yl)-benzenesulfonamide) were synthesized.The X-ray crystal structures of the complexes have been determined. Interaction of complexes with the DNA molecule and cytotoxicity studies were carried out.

Anionic Amidinourea–Metal(II) Tautomers: MN2O2 or MN4?

Abstract Structures of amidinourea–metal complexes have been obscured by subtle tautomerism and crystal waters. To clarify the most stable form of the tautomers, bis(amidinourea)copper(II) anhydride and the alkyl derivatives were synthesized under basic conditions, and the stability of the CuN2O2 chromophore was suggested. From substituent effects of chelations, UV–vis spectra, IR/Raman spectra, and DFT calculations, it was suggested that the bis(amidinourea)copper(II) has a CuN2O2 chromophore, not CuN4 chromophore. The mutual exclusion rule of IR/Raman spectra supported the trans-CuN2O2 chromophore. Systematic calculations on bis(amidinourea)–Cu(II), –Ni(II), –Pd(II), –Zn(II), and –Cd(II) chelates revealed that the robust stability of CuN2O2 chromophores originates from quasi aromaticity in the six-membered chelate rings. cis- or trans-CuN4 stability reported in the early references is suspicious.

The replacement of chlorides by cytosines in copper(II) complexes containing guanidine derivatives

Two copper(II) chloride complexes of amidino-O-methylurea (L1), [Cu(L1)Cl2] (1), and (N-benzyl)-amidino-O-methylurea (L2), [Cu(L2)Cl2] (2), were prepared and characterized by elemental analysis, infrared, diffuse reflectance, electron spin resonance and electrospray ionization mass spectra. Their cytosine binding abilities has been studied and found that two cytosine molecules are able to coordinate with the copper centers by replacing the chloride ligands to yield the bifunctional binding adducts [Cu(L1)(cyt)2]Cl2 (1c) and [Cu(L2)(cyt)2]Cl2 (2c), respectively. The shift of the CO band of cytosine in both cytosine-bound products to higher energy suggested that the N(3)–cytosine atom coordinates to the copper center. The large blue shifts of the d–d absorbance maxima and the nine superhyperfine splitting from the CuN4 chromophore were also observed in their electronic and EPR spectra. Their thermal decompositions have also supported the interaction of cytosine with complexes 1 and 2. Density functional calculations have also been performed and revealed that square planar coordination geometry is more stable for both 1c and 2c. The binding energy of 1c is found to be ∼20% lower than that of 2c, indicative of the higher binding potential of 1c.

New metal chelates of 5-amino-4-azopyrazoles: The crystal and molecular structure of bis{1-phenyl-3-methyl-4-(p-tolyl)azo-5-(p-carboxymethoxyphenyl)pyrazolamidato}copper(II)

The reactions of 1,3-alkyl(aryl) derivatives of 5-amino-4-azopyrazoles (HL) with copper(2+) acetate afford metal chelates CuL2. Complexes with the CuN4 chromophore containing a substituted amino group (X = NR) as a donor, like their azomethine analogues, have a pseudotetrahedral structure. Copper chelates with X = NH are planar. The X-ray diffraction data and an additional hyperfine structure (ahfs) from 15N atoms of the azo group in the labeled complexes provide evidence for the formation of six-membered metallocycles. The coordination polyhedron in bis{1-phenyl-3-methyl-4-(p-tolyl)azo-5-(p-carboxymethoxyphenyl)pyrazolamidato}Cu(II) can be described as a pseudotetrahedron.

Mixed-ligand copper(II) complexes of dipicolylamine and 1,10-phenanthrolines: The role of diimines in the interaction of the complexes with DNA

Mixed-ligand copper(II) complexes of the type [Cu(dipica)(diimine)](ClO4)2, where dipica is di(2-picolyl)amine and diimine is 1,10-phenanthroline (phen), 5,6-dimethyl-1,10-phenanthroline (5,6-dmp), 2,9-dimethyl-1,10-phenanthroline (2,9-dmp) or dipyridoquinoxaline (dpq), have been isolated and characterized by analytical and spectral methods. The copper(II) complexes exhibit a broad band in the visible region around 675 nm and axial EPR spectra in acetonitrile glass (77 K) with g∥ and A∥ values of ∼2·22 and 185 × 10−4 cm−1 respectively, suggesting the presence of a square-based coordination geometry for the CuN5 chromophore involving strong axial interaction. The interaction of the complexes with CT DNA has been studied using absorption, emission and circular dichroic spectral methods and viscosity measurements. Absorption spectral titrations reveal that the intrinsic DNA binding affinities are dependent upon the nature of the diimine ligand: dpq > 5,6-dmp > phen > 2,9-dmp. This suggests the involvement of the diimine rather than the dipica ‘face’ of the complexes in DNA binding. An intercalative mode of DNA interaction, which involves the insertion of dpq and to a lesser extent the phen ring of the complexes in between the DNA base pairs, is proposed. However, interestingly, the 5,6-dmp complex is involved in hydrophobic interaction of the 5,6-dmp ring in the grooves of DNA. The large enhancement in the relative viscosity of DNA on binding to the dpq and 5,6-dmp complexes supports the proposed DNA binding modes. Further, remarkably, the 5,6-dmp complex is selective in exhibiting a positive-induced CD band on binding to DNA suggesting the transition of the B form of CT DNA to A-like conformation. The variation in relative emission intensities of DNA-bound ethidium bromide observed upon treatment with the complexes parallels the trend in DNA binding affinities.

Synthesis and Structure of Tetraploid (Imidazole) Copper (II) Terephthalate, [Cu(Im)4] (teph)

AbstractThe crystal structure of [Cu (Im)4] (teph) (Im = imidazole, teph = terephthalate) has been determined by X‐ray crystallography. It crystallizes in the triclinic system, space group Pī with cell dimensions of a = 0.80356 (16) nm, b = 0.84269 (17) run, c = 0.88967 (18) nm, α = 76.90 (3)°, β = 68.95 (3)°, γ = 75.94 (3)°, and Z = 1. Its structure of the title compound is composed of discrete monomelic molecule of [Cu (Im)4]‐(teph). The copper (II) ions have a square plane geometry with the CuN4 chromophore.

Bispidine copper(II) compounds: effects of the rigid ligand backbone.

Approximative density-functional theory calculations indicate that the tetradentate ligand L (L = 2,4-bis-(2-pyridyl)-3,7-diaza-[3.3.1]-bicyclononane) enforces an unusual and strong binding of a co-ligand (substrate) to a copper(II) center. The co-ligand in [Cu(L)(Cl)](+) completes a square-pyramidal coordination around copper(II) and binds in the equatorial plane rather than on the apical position. This configuration is a stable geometric isomer for the model complex [Cu(NH3)2(imine)2(Cl)](+), but it is disfavored by approximately 10 kJ mol(-1) and not commonly observed for CuN4 chromophores with a monodentate co-ligand. The equatorial coordination increases the bond energy of the copper(II)-chloride bond by approximately 80 kJ mol(-1), and similar results are expected for other copper(II)-L-substrate complexes, some of which show strong catalytic activity or unusual stability. Despite the enforced configuration, L does not impose significant steric strain on the copper(II) center but is well preorganized for the Jahn-Teller labile ion in this unusual geometry. The preorganization extends to the orientation of the pyridine donors (torsion angle around the copper-pyridine bond), and this seems to be of importance in the reactivity of the copper-L complexes and their derivatives.

Crystal structure, redox and spectral properties of copper(II) complexes with macrocyclic ligands incorporating both oxamido and imine groups

The electrochemical and spectral behaviors of three copper(II) complexes [CuL1] 1, [CuL2] 2 and [CuL3] 3, where L1, L2 and L3 are the dianions of macrocyclic oxamido Schiff bases, have been investigated by cyclic voltammetry, electronic and ESR spectra. These macrocyclic complexes, which incorporate both oxamido and imine groups, can undergo quasi-reversible reduction (CuII → CuI) and oxidation (CuII → CuIII). The crystal structures of 1 and 2 have been determined by single-crystal X-ray analysis. The difference in ring size leads to significant differences in molecular and crystal structure, electronic and ESR spectra and redox behavior. In the [14]N4 macrocyclic complex, 2, the CuN4 chromophore assumes a nearly square-planar co-ordination geometry, but the geometry in the [15]N4 macrocyclic complex, 1, is distorted towards tetrahedral. The results from spectroscopic and redox studies are consistent with the crystallographic results and perfectly related to each other. The main factors that determine the relative stability of CuI and CuIII in these complexes are the size, geometry and flexibility of the co-ordination cavity.

Anion recognition by conservation of hydrogen-bonding patterns in salts of copper(II) co-ordinated by tetradentate bis(amidino-O-alkylurea) ligands †

Refluxing 1,2-bis(2-cyanoguanidino)ethane (L1) in methanol or ethanol containing copper(II) sulfate resulted in the formation of [CuL3m][MeOSO3]2 {L3m = [HNC(OMe)NHC(NH2)NCH2]2} and [CuL3e][EtOSO3]2 {L3e = [HNC(OEt)NHC(NH2)NCH2]2}. Structural analysis of these complexes has revealed hydrogen-bonded supramolecular architectures constructed from [CuLi]2+ cations with square planar CuN4 chromophores and [ROSO3]− anions. The basic supramolecular synthon is a 1-D chain of alternating cations and anions, a motif which is also found with Cl− and [BF2(OMe)2]− anions. The [ROSO3]− anion is an ideal fit for the space between two cations; its hydrophobic O-alkyl group is surrounded by the O-alkyl groups of the cations and its hydrophilic SO3− moiety forms N–H⋯O hydrogen bonds with their amino and imino functionalities. In [CuL3m][MeOSO3]2 the chains, which are linear, are hydrogen bonded through a second methyl sulfate anion to give a 2-D sheet motif. The sheets are bound together to form a 3-D framework through very weak Cu⋯O co-ordinative interactions which complete a tetragonally elongated octahedral geometry for the copper(II) centre. In [CuL3e][EtOSO3]2 the chains, which are sinusoidal, are hydrogen bonded through a second ethyl sulfate anion to give a bilayered arrangement. The bilayers aggregate into a 3-D framework by a combination of hydrogen bonding and weak Cu⋯O co-ordinative interactions which result in a square pyramidal co-ordination geometry for the copper(II) centre. Despite the fit between [CuLi]2+ cations and alkyl sulfate anions in the chain, when a mixture of anions (chloride and ethyl sulfate) is present in the crystallisation medium, the preferred chain supramolecular synthon of the product, [CuL3e][EtOSO3]Cl·2H2O, is that containing chloride. The ethyl sulfate anions are involved, together with water molecules, in a complex hydrogen-bonding network which connects the chains into 2-D sheets, which are assembled, in turn, into a 3-D network structure by a combination of hydrogen bonding networks and exceedingly weak Cu⋯Cl co-ordinative interactions, which give rise to a square pyramidal copper(II) co-ordination geometry.

Synthesis and characterization of binuclear and polymeric five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn): Crystal structure of [Cu(trpn)(N 3)]ClO 4 ( I) and [Cu 2(trpn)(tren)(NO 2)(H 2O)](ClO 4) 3 ( II)

The synthesis and characterization of five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn) are described. The X-ray diffraction studies have established the structures [Cu(trpn)(N 3)]ClO 4 ( I) and [Cu 2(trpn)(tren)(NO 2)(H 2O)](ClO 4) 3 ( II). Compound ( I) consists of a polymeric cation chain and ClO 4 − counter ions. The coordination geometry of the Cu(II) centers may be described as distorted square pyramidal (SP) with the azido group at the apical site and three nitrogen donors of the trpn molecule occupy the basal sites. The CuN5 chromophore is completed by a bridging aminopropyl group of neighboring trpn ligand. Compound ( II) is a dinuclear complex cation with two different cation geometries in the unit cell. The geometry of the Cu(II) binding tren ligand is close to trigonal bipyramidal (TBP), with the basal and apical sites are occupied by the four nitrogen atoms of the tren ligand. The fifth coordination site is bridged to one of the aminopropyl arms of the trpn ligand. The geometry of the second Cu(II) center may be described as close to distorted SP, where the trpn ligand is binding the Cu(II) ion via the two primary aminopropyl groups and the tertiary nitrogen. The remaining two sites are occupied by oxygen atoms of a water molecule and nitrite ion. The intramolecular Cu…Cu distance in I and II ranges from 7.55 Å to 7.94 Å. The visible spectra of the complexes in DMSO are consistent with the X-ray results found for I and II and show a greater tendency toward SP geometry.