A new diaza‐18‐crown‐6 ligand containing two quinolin‐8‐ylmethyl side arms: Crystal structures and characterization of the ligand,the protonated ligand and its mononuclear barium(II) and dinuclear copper(II) complexes

A new 7,16‐bis(quinolin‐8‐ylmethyl)‐1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane ligand, L, has been prepared and its crystal structure reported. In addition, the structure of the protonated ligand H₂L has been determined. H₂L is of interest because of interatomic interactions between the ligand and perchlorate ions. The mononuclear Ba(II) (Ba L ), and dinuclear Cu(II) (Cu₂L) complexes of L have been prepared and their crystal structures determined. Stability constants and other thermodynamic data valid in methanol at 23 or 25° for these and several other complexes of L have been obtained. Among the metal ions studied, L forms the most stable complex with Ba²⁺. In addition, L selectively binds Cu²⁺ over Ni²⁺ by about 3 orders of magnitude. Some of the complexes have been studied using nmr and uv‐vis spectroscopic techniques. Crystal data are given for L, space group, P2₁c, a = 8.8325(14) Å, b = 13.808(3) Å, c = 13.310(3) Å; β = 94.72(2)° Z=2, R = 0.0727; for H₂ L , space group, P2₁/c, a = 14.685(3) Å, b = 15.035(6) Å, c = 17.369(4) Å, β = 90.366(12)°, Z = 4, R = 0.0781; for Ba L , space group, Pbcn, a = 17.314(3) Å, b = 9.539(2) Å, c = 22.081(3) Å, Z = 4, R = 0.0354; and for Cu₂ L , space group, Cc, a = 19.762(2) Å, b = 14.413(2) Å, c = 14.935(2) Å, β = 98.753(12)°, Z = 4, R = 0.0564. Cu²⁺ forms a hydroxo‐bridged dinuclear complex with L while Ba²⁺ forms a mononuclear complex with L in which its two side arms are not involved in complexation.     

Synthesis,characterization, coordination and antibacterial properties of novel asymmetric 1,1′‐disubstituted ferrocene‐derived Schiff‐base ligands and their Co(II), Cu(II) Ni(II) and Zn(II) complexes

Some new asymmetric 1,1 ′‐disubstituted ferrocene‐derived Schiff‐bases have been prepared and used as ligands in the preparation of their Co(II), Cu(II), Ni(II) and Zn(II) metal chelates. These synthesized ligands and their metal chelates have been characterized by their physical, analytical and spectral data. These have also been used for screening against pathogenic bacterial species, e.g. Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonae and have been found to be a novel class of organometallic‐based antibacterials. Copyright © 2001 John Wiley & Sons, Ltd.     

trans‐Dichloridobis(4,8‐dimethyl‐2‐phenyl‐2‐phosphabicyclo[3.3.1]nonane‐κP)platinum(II)

The crystal structure of the title compound, trans‐[PtCl₂(C₁₆H₂₃P)₂], has been determined at 100 K. The Pt atom is located on a twofold axis and adopts a distorted square‐planar coordination geometry. The structure is only the second example of a coordination complex containing a derivative of the 4,8‐dimethyl‐2‐phosphabicyclo[3.3.1]nonane (Lim) phosphine ligand family. The ligand contains four chiral C atoms, with the stereochemistry at three of these fixed during synthesis, therefore resulting in two possible ligand stereoisomers. The compound crystallizes in the chiral space group P4₃2₁2 but is racemic, comprising an equimolar mixture of both stereoisomers disordered on a single ligand site. The effective cone angles for both isomers are the same at 146°.     

Synthesis,spectroscopic properties,density functional theory calculations and nonlinear optical properties of novel complexes of 5‐hydroxy‐4,7‐dimethyl‐6‐(phenylazo)coumarin with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions

5‐Hydroxy‐4,7‐dimethyl‐6‐(phenylazo)coumarin (L) has been synthesized and its novel complexes with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions have also been prepared and identified using various analytical tools. The complexes are octahedral binding via one/two oxygen, nitrogen atoms for 1:1 and 1:2 complexes and two/three coordinated water molecules. All the prepared solid complexes behave as neutral in dimethylformamide. The optimized structures of the studied complexes were theoretically investigated at the B3LYP/6‐311G** level. Molecular stability and bond strengths were investigated by applying natural bond orbital analysis. The geometries of the studied complexes are non‐planar as indicated from the values of dihedral angles. The global properties of hardness, global softness and electronegativity were computed. The calculated small energy gap between highest occupied and lowest unoccupied molecular orbital energies shows that charge transfer occurs within the complexes. The obtained total static dipole moment, mean polarizability, anisotropy of polarizability and mean first‐order hyperpolarizability (<β>) were compared with those of urea as a reference material. The results for <β> showed that the complexes are excellent candidates as nonlinear optical materials. The three‐dimensional plots of the molecular electrostatic potential for some selected complexes were investigated.     

Crystal structures of two Ca(II) complexes with imidazole-4,5-dicarboxylate and water ligands

The structure of compound I: poly-diaqua(μ-imidazole-4,5-dicarboxylato-N,O; -O′; -O′′, -O′′′) calcium(II) monohydrate [Ca(C₅H₂N₂O₄)(H₂O)₂·H₂O] is built of molecular sheets in which imidazole-4,5-dicarboxylate ligands bridge the metal ions using both carboxylate groups, each bidentate. Ca(II) is coordinated by six oxygen atoms and one hetero-ring nitrogen atom distributed at the apices of a capped tetragonal bipyramid. The basal plane of the pyramid is formed by two carboxylate oxygen atoms [d(Ca–O2?=?2.374(1)?Å, d(Ca–O4)?=?2.412(1)?Å] and two water oxygen atoms [d(Ca–O5)?=?2.384(1)?Å, d(Ca–O6)?=?2.455(1)?Å], the capped position is occupied by the carboxylate oxygen atom O3 [d(Ca–O3)?=?2.325(1)?Å], the hetero-ring nitrogen atom [d(Ca–N2)?=?2.523(1)?Å] and the carboxylate oxygen atom O4 [d(Ca–O2)?= 2.412(1)?Å] form the apices of the prism. The solvation water molecule plays a significant role in a framework of hydrogen bonds responsible for the stability of the crystal. The structure of compound II: trans-tetraquadi(H-imidazole-4,5-dicarboxylato-N,O) calcium(II) monohydrate, [Ca(C₅H₃N₂O₄)₂(H₂O)₄·H₂O] consists of monomers in which the Ca(II) ion is located on a centre of symmetry. The coordination around the Ca(II) is a strongly deformed pentagonal bipyramidal with the imidazole-4,5-dicarboxylate (4,5-IDA) ligands in the trans arrangement forming a dihedral angle of 68.3°. An imidazole-ring nitrogen atom [d(Ca–N)?=?2.632(2)?Å] and one carboxylate O atom [d(Ca–O)?=?2.531(2)?Å] from each ligand coordinate to the metal ion. The coordination is completed by four water oxygen atoms [d(Ca–O)?=?2.393(2)?Å] and [d(Ca–O)?=?2.367(2)?Å]. The coordinated water molecules act as hydrogen bond donors and acceptors to the unbonded carboxylate oxygen atoms in adjacent monomers giving rise to a three-dimensional molecular network.     

Crystallographic report: Bis[N,N‐dimethyl‐N′‐(pyrid‐2‐ylmethyl)‐ethylenediamine]zinc(II) diperchlorate

The zinc(II) atom in the centrosymmetric complex is in a distorted N₆ octahedral geometry defined by two tridentate ligands. Copyright © 2004 John Wiley & Sons, Ltd.     

Novel 13,14‐dimethyl‐5,8‐dioxa‐2,11,13,14‐tetraaza‐1,12‐diphosphabicyclo [10.1.1] tetradecane 1,12‐dioxide ligand and its Ni(II), Co(II), and Cu(II) complexes: Synthesis,characterization, antimicrobial,DNA cleavage,and computational studies

A novel diazadiphosphetidine ligand derived from the reaction of 2,4‐dichloro‐1,3‐dimethyl‐1,3,2,4‐diazadiphosphetidine‐2,4‐dioxide and 2,2′‐(ethane‐1,2‐diylbis[oxy])bis(ethan‐1‐amine) and its Ni(II), Cu(II), and Co(II) complexes have been synthesized, characterized by spectroscopic, elemental analyses, magnetic susceptibility, and conductivity methods, and screened for antimicrobial, DNA binding, and cleavage properties. Spectroscopic analysis and elemental analyses indicate the formula [M(H₂L)Cl₂] for the Cu(II), Co(II), Ni(II), and Zn(II) complexes and octahedral geometry for all the complexes. The non‐electrolytic nature of the complexes in dimethyl sulfoxide (DMSO) was confirmed by their molar conductance values, which are in the range 12.32–6.73 Ω^?1 cm² mol^?1. Computational studies have been carried out at the density functional theory (DFT)‐B3LYP/6‐31G(d) level of theory on the structural and spectroscopic properties of diazadiphosphetidine H₂L and its binuclear Cu(II), Co(II), Ni(II), and Zn(II) complexes. Six tautomers and geometrical isomers of the diazadiphosphetidine ligand were confirmed using semiempirical AM1 and DFT method from DMOL³ calculations. The copper complex had the best antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA by agarose gel electrophoresis in the presence and absence of an oxidant (H₂O₂) and a free‐radical scavenger (DMSO), indicated no activity for the ligand and moderate activity for the complexes, with the copper complex cleaving pBR322 DNA more efficiently in the presence of H₂O₂.     

Synthesis,spectral and antibacterial activity of Co(II), Ni(II) and Zn(II) complexes with 2‐hydroxy‐benzoic acid(3,4‐dihydro‐2H‐naphthalen‐1‐ylidene)‐hydrazide

A bioactive Schiff base HL i.e. 2‐hydroxy‐benzoic acid(3,4‐dihydro‐2H ‐naphthalen‐1‐ylidene)‐hydrazide was synthesized by reacting equimolar amount of salicylic acid hydrazide and 1‐tetralone. Co(II), Ni(II) and Zn(II) complexes of ligand HL was synthesized in 1:1 and 1:2 molar ratio of metal to ligand. The structure of the synthesized ligand and metal complexes was established by elemental analysis, molar conductance, magnetic susceptibility measurements, electronic, IR and EPR spectral techniques. For determining the thermal stability the TGA has been done. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6–31 + g(d,p) basis set. Spectral data reveal that ligand behave uninegative tridentate in ML complexes and uninegative bidentate in ML₂ complexes. On the basis of characterization octahedral geometry has been assigned for Co(II) and Ni(II) complexes, while tetrahedral for Zn(II) complexes. Antibacterial activity of the synthesized compounds were evaluated against Staphylococcus aureus , Bacillus subtilis, Escherichia coli , Xanthomonas campestris and Pseudomonas aeruginosa and the results revealed that metal complexes show enhanced activity in comparison to free ligand.     

Co(II), Ni(II), Cu(II) and Zn(II) complexes of isatinyl‐2‐aminobenzoylhydrazone: synthesis,characterization and anticancer activity

This article describes the synthesis, structural aspects and biological studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes of a new hydrazone derived from the condensation of isatin and 2‐aminobenzoylhydrazide. The ligand is well characterized using ¹H NMR, ¹³C NMR, 2D HETCOR, mass and IR spectral studies. The chelating tendency of the ligand towards transition metal ions is established using analytical and spectral studies, which reveal the monobasic tridentate nature of the ligand. Octahedral geometry for Co(II), Cu(II) and Zn(II) and tetrahedral geometry for Ni(II) are tentatively proposed. All the synthesized compounds were screened for in vitro anticancer activity against Ehrlich ascites carcinoma and human cancer cell lines (adenocarcinoma HT29, kidney cancer cell line K293 and breast cancer cell line MDA231) using tryphan blue exclusion method and MTT assay. Copyright © 2014 John Wiley & Sons, Ltd.     

Methanol[1‐(methoxymethanimidoyl)‐2‐(pyridin‐2‐ylmethyl)guanidine]bis(perchlorato)copper(II)

The title complex, [Cu(ClO₄)₂(C₉H₁₃N₅O)(CH₃OH)], was synthesized from a methanolysis reaction of N‐(methylpyridin‐2‐yl)cyanoguanidine (L³) and copper(II) perchlorate hexahydrate in a 1:1 molar ratio. The Cu^II ion is six‐coordinated by an N₃O₃ donor set which confers a highly distorted and asymmetric octahedral geometry. Three N‐donor atoms from the chelating 1‐(methoxymethanimidoyl)‐2‐(pyridin‐2‐ylmethyl)guanidine (L^3m) ligand and one O atom from the methanol molecule define the equatorial plane, with two perchlorate O atoms in the apical sites, one of which has a long Cu—O bond of 2.9074 (19) Å. The dihedral angle between the five‐ and six‐membered chelate rings is 8.21 (8)°. Two molecules are associated into a dimeric unit by intermolecular N—H...O(perchlorate) hydrogen bonds. Additionally, the weakly coordinated perchlorate anions also link adjacent [Cu(ClO₄)₂(L^3m)(CH₃OH)] dimers by hydrogen‐bonding interactions, resulting in a two‐dimensional layer in the (100) plane. Further C—H...O hydrogen bonds link the two‐dimensional layers along [100] to generate a three‐dimensional network.     

Cobalt(II) chloride complexes with 1,1′‐dimethyl‐4,4′‐bipyrazole featuring first‐ and second‐sphere coordination of the ligand

In catena‐poly[[dichloridocobalt(II)]‐μ‐(1,1′‐dimethyl‐4,4′‐bipyrazole‐κ²N²:N^2′)], [CoCl₂(C₈H₁₀N₄)]_n, (1), two independent bipyrazole ligands (Me₂bpz) are situated across centres of inversion and in tetraaquabis(1,1′‐dimethyl‐4,4′‐bipyrazole‐κN²)cobalt(II) dichloride–1,1′‐dimethyl‐4,4′‐bipyrazole–water (1/2/2), [Co(C₈H₁₀N₄)₂(H₂O)₄]Cl₂·2C₈H₁₀N₄·2H₂O, (2), the Co²⁺ cation lies on an inversion centre and two noncoordinated Me₂bpz molecules are also situated across centres of inversion. The compounds are the first complexes involving N,N′‐disubstituted 4,4′‐bipyrazole tectons. They reveal a relatively poor coordination ability of the ligand, resulting in a Co–pyrazole coordination ratio of only 1:2. Compound (1) adopts a zigzag chain structure with bitopic Me₂bpz links between tetrahedral Co^II ions. Interchain interactions occur by means of very weak C—H...Cl hydrogen bonding. Complex (2) comprises discrete octahedral trans‐[Co(Me₂bpz)₂(H₂O)₄]²⁺ cations formed by monodentate Me₂bpz ligands. Two equivalents of additional noncoordinated Me₂bpz tectons are important as `second‐sphere ligands' connecting the cations by means of relatively strong O—H...N hydrogen bonding with generation of doubly interpenetrated pcu (α‐Po) frameworks. Noncoordinated chloride anions and solvent water molecules afford hydrogen‐bonded [(Cl⁻)₂(H₂O)₂] rhombs, which establish topological links between the above frameworks, producing a rare eight‐coordinated uninodal net of {4²⁴.5.6³} ( ilc ) topology.     

Mononuclear Co(III), Ni(II) and Cu(II) complexes of 2‐(2,4‐dichlorobenzamido)‐N'‐(3,5‐di‐tert‐butyl‐2‐hydroxybenzylidene)benzohydrazide: Structural insight and biological assay

A series of mononuclear metal complexes of Co(III), Ni(II) and Cu(II) with 2‐(2,4‐dichlorobenzamido)‐N′‐(3,5‐di‐tert‐butyl‐2‐hydroxybenzylidene)benzohydrazide ( LH ₃ ) have been synthesized and characterized using various physico‐chemical, spectroscopic and single crystal X‐ray diffraction techniques. Structural studies of [Co( LH )( LH ₂ )]·H₂O ( 4 ) revealed the presence of both amido and imidol tautomeric forms of LH ₃ , resulting in a distorted octahedral geometry around the Co(III) ion. [Ni( LH )(H₂O)]·H₂O ( 5 ) and [Cu( LH )(H₂O)]·H₂O ( 6 ) are isomorphous structures and crystallize in the monoclinic P2₁/c space group. The crystal structures of 4 , 5 and 6 are stabilized by hydrogen bonds formed by the enclathrated water molecules, C‐H···π and π···π interactions. Complexes along with the ligand ( LH ₃ ) were screened for their in vivo anti‐inflammatory activity (carrageenan‐induced rat paw edema method) and in vitro antioxidant activity (DPPH free radical scavenging assay). Metal complexes have shown significant anti‐inflammatory and antioxidant potential.     

trans‐Dichloridotetrakis(3,5‐dimethylpyridine)copper(II)

The title compound, [CuCl₂(C₇H₉N)₄], lies on a site of crystallographic 42 (D₄) symmetry in the space group P4/nnc, and is isomorphous with the Ni and Co analogues. The Cu and Cl atoms thus lie on a fourfold axis, and the 3,5‐lutidine ligands lie on twofold axes. The Cu—Cl distance is 2.7649 (7) Å and the Cu—N distance is 2.0510 (12) Å. The space group of the Co analogue is revised from Pnnn to P4/nnc.     

Mononuclear nickel(II) and zinc(II) complexes with deprotonated forms of the tripodal hexadentate ligand 1,3‐bis(2‐hydroxybenzylidene)‐2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methylpropane‐1,3‐diamine

In the crystal structures of both title compounds, [1,3‐bis(2‐hydroxybenzylidene)‐2‐methyl‐2‐(2‐oxidobenzylideneaminomethyl)propane‐1,3‐diamine]nickel(II) [2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methyl‐1,3‐bis(2‐oxidobenzylidene)propane‐1,3‐diamine]nickel(II) chloride methanol disolvate, [Ni(C₂₆H_25.5N₃O₃)]₂Cl·2CH₄O, and [1,3‐bis(2‐hydroxybenzylidene)‐2‐methyl‐2‐(2‐oxidobenzylideneaminomethyl)propane‐1,3‐diamine]zinc(II) perchlorate [2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methyl‐1,3‐bis(2‐oxidobenzylidene)propane‐1,3‐diamine]zinc(II) methanol trisolvate, [Zn(C₂₆H₂₅N₃O₃)]ClO₄·[Zn(C₂₆H₂₆N₃O₃)]·3CH₄O, the 3d metal ion is in an approximately octahedral environment composed of three facially coordinated imine N atoms and three phenol O atoms. The two mononuclear units are linked by three phenol–phenolate O—H...O hydrogen bonds to form a dimeric structure. In the Ni compound, the asymmetric unit consists of one mononuclear unit, one‐half of a chloride anion and a methanol solvent molecule. In the O—H...O hydrogen bonds, two H atoms are located near the centre of O...O and one H atom is disordered over two positions. The Ni^II compound is thus formulated as [Ni(H_1.5L)]₂Cl·2CH₃OH [H₃L is 1,3‐bis(2‐hydroxybenzylidene)‐2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methylpropane‐1,3‐diamine]. In the analogous Zn^II compound, the asymmetric unit consists of two crystallographically independent mononuclear units, one perchlorate anion and three methanol solvent molecules. The mode of hydrogen bonding connecting the two mononuclear units is slightly different, and the formula can be written as [Zn(H₂L)]ClO₄·[Zn(HL)]·3CH₃OH. In both compounds, each mononuclear unit is chiral with either a Δ or a Λ configuration because of the screw coordination arrangement of the achiral tripodal ligand around the 3d metal ion. In the dimeric structure, molecules with Δ–Δ and Λ–Λ pairs co‐exist in the crystal structure to form a racemic crystal. A notable difference is observed between the M—O(phenol) and M—O(phenolate) bond lengths, the former being longer than the latter. In addition, as the ionic radius of the metal ion decreases, the M—O and M—N bond distances decrease.     

New polynuclear carbonyl ruthenium (II) complexes derived from 1,8‐naphthyridine

This work shows the synthesis and characterization of new carbonyl complexes derived of 1,8‐naphthyridine. Covalently bonded complex can be successfully employed in building of supramolecular structures. Copyright © 2005 John Wiley & Sons, Ltd.     

Two new Co(II) and Ni(II) complexes with 3-(2-Pyridyl)pyrazole-based ligand: synthesis, crystal structures, and bioactivities

Two new Co(II) and Ni(II) complexes exhibiting DNA cytotoxic activities with 3-(2-pyridyl)pyrazole-based ligand, [Co(L)(3)](ClO(4))(2) (1) and [Ni(L)(3)](ClO(4))(2) (2) (L=1-[3-(2-pyridyl)-pyrazol-1-ylmethyl]-naphthalene) were synthesized and structurally characterized. Both 1 and 2 crystallized in the monoclinic system, space group P2(1)/c, for 1, a=12.8324(8), b=12.1205(8), c=33.27(2) A, beta=93.92(3) degrees and Z=4; for 2, a=12.8764(3), b=12.1015(3), c=33.2415(9) A, beta=93.998(1) degrees and Z=4. Among them, the Co(II) and Ni(II) ions were all coordinated by six N donors from three distinct L ligands. In addition, the cytotoxic activities of 1, 2 and L in vitro were evaluated against three different cancer cell lines HL-60 (human leukemia), BGC-823 (stomach cancer) and MDA-MB-435 (mammary cancer), respectively. The results showed that 1 exhibited significantly high cytotoxic activities against HL-60 and moderate activities against BGC-823 and MDA-MB-435. In order to further investigate the relationships between structures and DNA-binding behaviors of these complexes, the interactions of 1, 2 and L with calf thymus DNA (CT-DNA) were then subjected to thermal denaturation, viscosity measurements and spectrophotometric methods. The results indicated that 1 and 2 intercalated with DNA via L ligand. The intrinsic binding constants of 1, 2 and L with DNA were 1.6x10(4), 5.6x10(3) and 2.76x10(3) M(-1), respectively.     

Synthesis of antibacterial and antifungal cobalt(II), copper(II), nickel(II) and zinc(II) complexes with bis‐(1,1′‐disubstituted ferrocenyl)thiocarbohydrazone and bis‐(1,1′‐disubstituted ferrocenyl)carbohydrazone

The condensation reaction of 1,1′‐diacetylferrocene with thiocarbohydrazide and carbohydrazide to form bis‐(1,1′‐disubstituted ferrocenyl)thiocarbohydrazone and bis‐(1,1′‐disubstituted ferrocenyl)carbohydrazone has been studied. The compounds obtained have been further used as ligands for their ligand and antimicrobial properties with cobalt(II), copper(II), nickel(II) and zinc(II) metal ions. The compounds synthesized have been characterized by physical, spectral and analytical methods and have been screened for antibacterial activity against Escherichia coli, Bacillus subtillis, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi, and for antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata using the agar well‐diffusion method. All the compounds synthesized have shown good affinity as antibacterial and antifungal agents, which increased in most of the cases on complexation with the metal ions. Copyright © 2004 John Wiley & Sons, Ltd.     

trans‐Di­aqua­bis(6‐hydroxy­picolinato‐κ2N,O2)copper(II)

In the title compound, [Cu(C₆H₄NO₃)₂(H₂O)₂], the Cu^II ion lies on an inversion centre and has an elongated octahedral environment, equatorially trans‐coordinated by two N,O‐bidentate picolinate ligands and axially coordinated by two water O atoms. The complex mol­ecules form layers, which are linked by O—H⋯O hydrogen bonds between the aqua ligands and neighbouring carboxyl­ate groups. An intramolecular hydrogen bond between the coordinated carboxyl­ate O atom and the hydroxy H atom is also observed.     

Crystal structures of two (5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane)iron(III) complexes

Reported in this contribution are the synthesis and crystal structures of two new Fe^III complexes of 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane (HMC), namely, dichlorido(5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane)iron(III) chloride, [FeCl₂(C₁₆H₃₆N₄)]Cl or cis‐[FeCl₂(rac‐HMC)]Cl ( 1 ), and dichlorido(5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane)iron(III) tetrachloridoferrate, [FeCl₂(C₁₆H₃₆N₄)][FeCl₄] or trans‐[FeCl₂(meso‐HMC)][FeCl₄] ( 2 ). Single‐crystal X‐ray diffraction studies revealed that both 1 and 2 adopt a pseudo‐octahedral geometry, where the macrocycles adopt folded and planar geometries, respectively. The chloride ligands in 1 are cis to each other, while those in 2 have a trans configuration. The relevant bond angles in 1 deviate substantially from an ideal octahedral coordination geometry, with the angles between the cis substituents varying from 81.55 (5) to 107.56 (4)°, and those between the trans‐ligating atoms varying from 157.76 (8) to 170.88 (3)°. In contrast, 2 adopts a less strained configuration, in which the N—Fe—N angles vary from 84.61 (8) to 95.39 (8)° and the N—Fe—Cl angles vary from 86.02 (5) to 93.98 (5)°.     

Co(II) and Ni(II) complexes incorporating <Emphasis Type="Italic">N</Emphasis>-acetimidoylacetamidine ligand: Synthesis and structures

Two new square planar complexes with the formula Co(L)₂ · CH₃OH (1) and Ni(L)₂ · CH₃OH (2) (HL = HN{C(Me)=NH}₂ = N-acetimidoylacetamidine) have been synthesized by solvothermal reactions in methanol/acetonitrile. N-acetimidoylacetamidine ligand was derived from the self-condensation reaction of acetonitrile, and the reaction was promoted by the cooperation of M(II) (M = Co in 1 and M = Ni in 2) with diphenylcarbazide. 1 and 2 are characterized by single crystal X-ray diffraction, elemental analysis and infrared spectrum. Both complexes crystallize in the monoclinic space group P2₁/c with a = 9.329(6) Å, b = 11.494(7) Å, c = 13.040(8) Å, β = 92.945(11)°, V = 1396.3(16) ų and Z = 4 for 1, and a = 9.323(4)Å, b = 11.512(5) Å, c = 13.020(6)Å, β = 92.819(7)°, V = 1395.7(10)ų and Z = 4 for 2.