Two new coordination polymers of Robson-type macrocycle bridged by perchlorate anions: Structure,electrochemistry and magnetism

Two new coordination polymers of Robson-type macrocycles, [Cu₂L¹(μ-ClO₄)₂]_∞ (1) and [Cu₂L²(μ-ClO₄)₂]_∞ (2) (where H₂L¹and H₂L² are the [2+2] condensation products of 2,6-diformyl-4-flurophenol with 1,3-diaminopropane and 2-hydroxy-1,3-diaminopropane, respectively), have been synthesized and characterized. The intriguing feature is that intermolecular perchlorato bridges occur between adjacent copper(II) centers. The cyclic voltammograms of the complexes show that each complex undergoes two pseudo-reversible processes with the half wave potentials, −0.361 V and −0.729 V for 1, and −0.372 V and −0.744 V for 2, respectively. Magnetic susceptibility was measured for 1 and 2 over a temperature range of 2–300 K. The optimized magnetic data were J = −359.6 cm⁻¹, j′ = −30 cm⁻¹ and R = 6.8 × 10⁻⁸ for 1 and J = −411 cm⁻¹, j′ = −26 cm⁻¹ and R = 2.4 × 10⁻⁷ for 2, respectively. The data reveal antiferromagnetic couplings between the copper(II) ions of intra- and intermolecular units.     

Synthesis, photophysical and electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine functionalized cyclometalating ligands

Four cyclometalated Pt(II) complexes, i.e., [(L²)PtCl] (1b), [(L³)PtCl] (1c), [(L²)PtCCC₆H₅] (2b) and [(L³)PtCCC₆H₅] (2c) (HL² = 4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-2,2′-bipyridine and HL³ = 4-[p-(N,N′-dibutyl-N′-phenyl)phenylene-diamino]-phenyl-6-phenyl-2,2′-bipyridine), have been synthesized and verified by ¹H NMR, ¹³C NMR and X-ray crystallography. Unlike previously reported complexes [(L¹)PtCl] (1a) and [(L¹)PtCCC₆H₅] (2a) (HL¹ = 4,6-diphenyl-2,2′-bipyridine), intense and continuous absorption bands in the region of 300-500 nm with strong metal-to-ligand charge transfer (¹MLCT) (dπ(Pt) → π^∗(L)) transitions (ε ∼ 2 × 10⁴ dm³ mol⁻¹ cm⁻¹) at 449-467 nm were observed in the UV-Vis absorption spectra of complexes 1b, 1c, 2b and 2c. Meanwhile, with the introduction of electron-donating arylamino groups in the ligands of 1a and 2a, complexes 1b and 2b display stronger phosphorescence in CH₂Cl₂ solutions at room temperature with bathochromically shifted emission maxima at 595 and 600 nm, relatively higher quantum yields of 0.11 and 0.26, and much longer lifetimes of 8.4 and 4.5 μs, respectively. An electrochromic film of 1b-based polymer was obtained on Pt or ITO electrode surface, which suggests an efficient oxidative polymerization behavior. An orange multilayer organic light-emitting diode with 1b as phosphorescent dopant was fabricated, achieving a maximum current efficiency of 11.3 cd A⁻¹ and a maximum external efficiency of 5.7%. The luminescent properties of complexes 1c and 2c are dependent on pH value and solvent polarity, which is attributed to the protonation of arylamino units in the C^N^N cyclometalating ligands.     

Synthesis and crystal structures of boratranes with methyl substituents on the atrane cage

Three monomeric boratranes B[(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n] (n = 0, 1; n = 1, 2; n = 2, 3) have been synthesized by the reaction of B(OMe)₃ with a series of triethanolateamines such as [(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]³⁻ (n = 0, L1; n = 1, L2; n = 2, L3), where the number of CMe₂ groups adjacent to the OH functionality varied from 3 (L1H₃) to 2 (L2H₃) to 1 (L3H₃). These boratranes 1-3 have been characterized by solution ¹H, ¹³C{¹H} and ¹¹B NMR, and the crystal structures of 1 and 2 have been determined by single crystal X-ray diffraction.     

Mononuclear Fe(III) and tetranuclear [Fe(III)Gd(III)]2 complexes with a Schiff-base ligand derived from the o-vanillin: Synthesis, crystal structures and magnetic properties

The mononuclear high-spin iron(III) complexes [Fe(3-MeOsalpn)Cl(H₂O)] (1) and [Fe(3-MeOsalpn)(NCS)(H₂O)]·0.5CH₃CN (2) and the tetranuclear oxo-bridged compound [{Fe(3-MeOsalpn)Gd(NO₃)₃}₂(μ-O)]·CH₃CN (3) [3-MeOsalpn²⁻ = N,N′-propylenebis(3-methoxysalicylideneiminate)] have been prepared and magneto-structurally characterised. The iron(III) ion in 1 and 2 is six-coordinated in a somewhat distorted octahedral surrounding with the two phenolate-oxygens and two imine-nitrogens from the Schiff-base building the equatorial plane and a water (1 and 2) and a chloro (1)/thiocyanate-nitrogen (2) in the axial positions. The neutral mononuclear units of 1 and 2 are assembled into centrosymmetric dinuclear motifs through hydrogen bonds between the axially coordinated water molecule of one iron centre and methoxy-oxygen atoms from the Schiff-base of the adjacent iron atom. The values of the intradimer metal-metal distance within the supramolecular dimers are 4.930 (1) and 4.878 Å (2). The tetranuclear of 3 can be described as two {Fe^III(3-MeOsalpn)} units connected through an oxo-bridge, each one hosting a [Gd^III(NO₃)₃] entity in the outer cavity defined by the two phenolate- and two methoxy-oxygen atoms. The values of the intramolecular Fe?Fe and Fe?Gd distances in 3 are 3.502 and 3.606 Å, respectively. The analysis of the magnetic data of 1-3 in the temperature range 1.9-300 K shows the occurrence of weak intermolecular antiferromagnetic interactions in 1 and 2 [J = −0.76 (1) and −0.75 cm⁻¹ (2) with the Hamiltonian defined as H = −JS_Fe1·S_Fe1] whereas two intramolecular antiferromagnetic interactions coexist in 3, one very strong between the two iron(III) ions (J₁) through the oxo bridge and the other much weaker between the iron(III) and the Gd(III) ions (J₂) across the double phenoxo oxygens [J₁ = −275 cm⁻¹ and J₂ = −3.25 cm⁻¹, the Hamiltonian being defined as H=-J₁S_Fe1·S_Fe1^′-J₂(S_Fe1·S_Gd1+S_Fe1^′·S_Gd1^′)]. These values are analysed in the light of the structural data and compared with those of related systems.     

Palladium and half sandwich ruthenium(II) complexes of selenated and tellurated benzotriazoles: Synthesis, structural aspects and catalytic applications

1-(Phenylselenomethyl)-1H-benzotriazole (L¹) and 1-(4-methoxyphenyltelluromethyl)-1H-benzotriazole (L²) have been synthesized by reacting 1-(chloromethyl)-1H-benzotriazole with in situ generated nucleophiles PhSe⁻ and ArTe⁻, respectively. The complexes of L¹ and L² with Pd(II) and Ru(II)(η⁶-p-cymene) have been synthesized. Proton, carbon-13, Se-77 and/or Te-125 NMR spectra authenticate both the ligands and their complexes. The single crystal structures of L¹, L² and [RuCl(η⁶-p-cymene)(L)][PF₆] (L = L¹: 3, L = L²: 4) have been solved. The Ru-Se and Ru-Te bond lengths have been found 2.4801(11) and 2.6183(10) Å, respectively. The palladium complexes, [PdCl₂(L)] (L = L¹: 1, L = L²: 2) have been explored for Heck and Suzuki-Miyaura C-C coupling reactions. The TON values are upto 95,000. The Ru-complexes have been found promising for catalytic oxidation of alcohols (TON ∼ 7.8-9.4 × 10⁴). The complexes of telluroether ligands are as efficient catalysts as those of selenoether ones and in fact better for catalytic oxidation.     

Dinuclear copper(II) perchlorate complexes with 6-(benzylamino)purine derivatives: Synthesis,X-ray structure,magnetism and antiradical activity

The reactions of Cu(ClO₄)₂·6H₂O with 6-(benzylamino)purine derivatives in a stoichiometric 1:2 metal-to-ligand ratio led to the formation of penta-coordinated dinuclear complexes of the formula [Cu₂(μ-L^1–8)₄(ClO₄)₂](ClO₄)₂·nsolv, where L¹ = 6-(2-fluorobenzylamino)purine (complex 1), L² = 6-(3-fluorobenzylamino)purine (2), L³ = 6-(4-fluorobenzylamino)purine (3), L⁴ = 6-(2-chlorobenzylamino)purine (4), L⁵ = 6-(3-chlorobenzylamino)purine (5), L⁶ = 6-(4-chlorobenzylamino)purine (6), L⁷ = 6-(3-methoxybenzylamino)purine (7) and L⁸ = 6-(4-methoxybenzylamino)purine (8); n = 0–4 and solv = H₂O, EtOH or MeOH. All the complexes have been fully characterized by elemental analysis, FTIR, UV–Vis and EPR spectroscopy, and by magnetic and conductivity measurements. Variable temperature (80–300 K) magnetic susceptibility data of 1–8 showed the presence of a strong antiferromagnetic exchange interaction between two Cu(II) (S = 1/2) atoms with J ranging from −150.0(1) to −160.3(2) cm⁻¹. The compound 6·4EtOH·H₂O was structurally characterized by single crystal X-ray analysis. The Cu?Cu separation has been found to be 2.9092(8) Å. The antiradical activity of the prepared compounds was tested by in vitro SOD-mimic assay with IC₅₀ in the range 8.67–41.45 μM. The results of an in vivo antidiabetic activity assay were inconclusive and the glycaemia in pre-treated animals did not differ significantly from the positive control.     

Chiral self-assembly of triorganotin complexes: Syntheses, characterization, crystal structures and antitumor activity of organotin(IV) complexes containing (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid ligands

Six new chiral triorganotin(IV) complexes, {(R₃Sn)₂[C₃H₆(COO)₂]}_n (R = Me: 1; Bu: 2), {(R₃Sn)₂[C₄H₈(COO)₂]}_n (R = Me: 3; Bu: 4), and {(R₃Sn)₂[C₂H₄O(COO)₂]}_n (R = Me: 5; Bu: 6) have been prepared by treatment of (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid, with the corresponding R₃SnCl (R = Me, Bu) and sodium ethoxide in methanol. All the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and TGA. Except for 3, all of the complexes were also characterized by X-ray crystallography. The structural analyses reveal that complexes 1 and 5 have 2D network structures in which (R)-(+)-methylsuccinic acid and l-(−)-malic acid act as tetradentate ligands coordinated to trimethyltin(IV) ions. Complexes 2 and 4 have 3D metal-organic framework structures in which the deprotoned acids serve as tetradentate ligands. Complex 6 adopts a 1D zigzag chain structure and forms a 2D supramolecular framework through intermolecular C-H?O interactions. In addition, the antitumor activities of complexes 1-6 have been studied. We also have measured the specific rotation of the chiral dicarboxylic acids and the organotin derivatives.     

Mononuclear Cu and dinuclear Cu–Ln complexes of benzimidazole based ligands including N and O donors: Syntheses,characterization, X-ray molecular structures and magnetic properties

The synthesis of two mononuclear precursor copper complexes, [(HL²)₂Cu], 1, and [(HL³)₂Cu]·H₂O, 2, and three dinuclear Cu–Ln complexes, [(HL¹)₂Cu(CH₃CN)₂Gd(NO₃)₃], 3, [(HL³)₂CuGd(NO₃)₃]·2(H₂O), 4, and [(HL³)₂CuTb(NO₃)₃]·2(H₂O), 5, based on the ligands H₂L¹ (4-bromo-2-[1-(5-bromo-2-hydroxy-3-methoxybenzyl)-1H-benzimidazol-2-yl]-6-methoxyphenol), H₂L² (2-(1H-benzimidazol-2-yl)-4-bromo-6-methoxyphenol) and H₂L³ (2-(1H-benzimidazol-2-yl)-6-methoxyphenol) are described in this contribution. The X-ray crystal structures of H₂L², 1, 3, 4, and 5 have been solved. The novel ligand H₂L² crystallizes with two independent molecules in the asymmetric unit; several intermolecular hydrogen contacts connect alternate independent H₂L² molecules into chains developing along c. In complex 1, two (HL²)⁻ ligands chelate the copper ion through their imidazolyl nitrogen and phenoxo oxygen atoms, in a relative head to tail arrangement. The molecular structure of 3 is similar to those of the previously reported Cu–Ln complexes of H₂L¹. In the isostructural complexes 4 and 5, two HL³ ligands sandwich one Cu²⁺ ion through their N,O sites and one Ln³⁺ ion through their O₂ site, implying a relative head to head arrangement, at variance with the relative head to tail arrangement of HL² in the mononuclear copper precursor 1. The magnetic properties of 1, 3, 4, and 5 have been investigated. Extended intermolecular antiferromagnetic interactions operate in complex 1 ((J_Chain = −0.8(1) cm⁻¹). Ferromagnetic interactions between Gd (S = 7/2) and Cu (S = 1/2) centers operate in complexes 3 and 4, leading to an S = 4 ground state (J_CuGd = 7.2(2) cm⁻¹ for 3 and J_CuGd = 6.5(2) cm⁻¹ for 4). Depopulation of the Tb Stark levels, preclude obtaining reliable information on the presence and sign of the Cu–Tb interaction in 5. These new complexes are complementary to those previously reported: the Cu–O₂–Gd core is planar while deformations are borne by the ligands at variance with previous examples where the constraints were located at the Cu–O₂–Gd core. The presence of two independent ligands in the Cu,Gd coordination spheres confers a degree of freedom greater than that allowed by a unique tetradentate ligand. As a result, the strength of the magnetic interaction is not solely related to the dihedral angle between the CuOO and GdOO planes in the central core.     

Syntheses,structures and hydrolytic properties of copper(II) complexes of asymmetrically N-functionalised 1,4,7-triazacyclononane ligands

A series of new asymmetrically N-substituted derivatives of the 1,4,7-triazacyclononane (tacn) macrocycle have been prepared from the common precursor 1,4,7-triazatricyclo[5.2.1.0^4,10]decane: 1-ethyl-4-isopropyl-1,4,7-triazacyclononane (L1), 1-isopropyl-4-propyl-1,4,7-triazacyclononane (L2), 1-(3-aminopropyl)-4-benzyl-7-isopropyl-1,4,7-triazacyclononane (L3), 1-benzyl-4-isopropyl-1,4,7-triazacyclononane (L4) and 1,4-bis(3-aminopropyl)-7-isopropyl-1,4,7-triazacyclononane (L5). The corresponding monomeric copper(II) complexes were synthesised and were found to be of composition: [Cu(L1)Cl₂] · 1/2 H₂O (C1), [Cu(L4)Cl₂] · 4H₂O (C2), [Cu(L3)(MeCN)](ClO₄)₂ (C3), [Cu(L5)](ClO₄)₂ · MeCN · NaClO₄ (C4) and [Cu(L2)Cl₂] · 1/2 H₂O (C5). The X-ray crystal structures of each complex revealed a distorted square-pyramidal copper(II) geometry, with the nitrogen donors on the ligands occupying 3 (C1 and C2), 4 (C3) or 5 (C4) coordination sites on the Cu(II) centre. The metal complexes were tested for the ability to hydrolytically cleave phosphate esters at near physiological conditions, using the model phosphodiester, bis(p-nitrophenyl)phosphate (BNPP). The observed rate constants for BNPP cleavage followed the order k_C1 ≈ k_C2 > k_C5 ? k_C3 > k_C4, confirming that tacn-type Cu(II) complexes efficiently accelerate phosphate ester hydrolysis by being able to bind phosphate esters and also form the nucleophile necessary to carry out intramolecular cleavage. Complexes C1 and C2, featuring asymmetrically disubstituted ligands, exhibited rate constants of the same order of magnitude as those reported for the Cu(II) complexes of symmetrically tri-N-alkylated tacn ligands (k ∼ 1.5 × 10⁻⁵ s⁻¹).     

Carbonylation of four-membered ruthenium and osmium metallacycles incorporating an orthometallated phenolic function: New acylruthenium and arylosmium complexes

The solution reaction of Ru(QL¹)(PPh₃)₂(CO)Cl (3) and Os(QL¹)(PPh₃)₂(CO)Br (4) with carbon monoxide at one atmosphere pressure has respectively afforded the orange acylruthenium system Ru(QL²)(PPh₃)₂(CO)Cl (5) and the yellow arylosmium dicarbonyl system Os(QL³)(PPh₃)₂(CO)₂Br (6) in excellent yields. (QL¹ is C₆H₂O-2-CHNHC₆H₄Q(p)-3-Me-5, QL² is C₆H₂(CO-1)O-2-CHNHC₆H₄Q(p)-3-Me-5 and QL³ is C₆H₂OH-2-CHNC₆H₄Q(p)-3-Me-5 and Q is Me, OMe and Cl.) It is proposed that in the case of 3 a dicarbonyl complex similar to 6 is formed as an intermediate which rapidly undergoes aryl migration with concomitant phenolato coordination furnishing 5. The stability of 6 is consistent with the greatly diminished ability of osmium in promotion of migratory reactions. In the reaction 4 → 6 the Os-O(phenolato) bond is cleaved and the Schiff base moiety undergoes iminium-phenolato → imine-phenol tautomerization. The observed cis geometry of 6 may arise by a concerted route involving edge displacement of the halide ligand. The crystal and molecular structure of 5(Q = Cl) has revealed the presence of a distorted octahedral RuC₂P₂OCl coordination sphere and a highly planar acyl chelate ring characterized by a Ru-C distance of 2.013(4) Å. In the hydrogen bonded zwitterionic iminium-phenolato ring the N ? O distance is 2.561(6) Å. The acyl complexes of type 5 display an MLCT band near 500 nm which is absent in 6. The Schiff base CN stretch in 5 (∼1630 cm⁻¹) is significantly higher than that in 6 (∼1600 cm⁻¹) which displays two strong CO stretches near 2020 and 1940 cm⁻¹ (cis-Os(CO)₂ configuration). A single ³¹P NMR signal occurs in both 5 and 6 near 37 and −6 ppm, respectively (trans-M(PPh₃)₂ configuration). The voltammetric reduction potentials of the M^III/M^II couple is observed near 1.0 and 0.8 V vs. SCE in 5 and 6, respectively. Both are significantly higher than those in parent complexes (3 and 4) due to stabilization of the bivalent state upon carbonylation.     

meta-Phenylene-bridged double Schiff base copper(II) complexes as building blocks for 1D coordination polymers: Synthesis,crystal structure and magnetic properties

The new double Schiff-base ligands H₆ipa-hyhb and H₆ipa-hyhh were synthesized by condensation of a 4,6-diformylresorcinol derivative (ipa) with 4-hydroxy-butanoic acid hydrazide (hyhb) and 6-hydroxy-hexanoic acid hydrazide (hyhh). The reaction with copper(II) perchlorate in the presence of an appropriate co-ligand (Him = imidazole, Hpz = pyrazole) leads to the novel coordination polymers {[Cu₂(H₄ipa-hyhb)(Hpz)₂](ClO₄)₂}_n (1), {[Cu₂(H₄ipa-hyhb)(Him)₂](ClO₄)₂}_n (2), and {[Cu₂-(H₄ipa-hyhh)(Hpz)₂](ClO₄)₂}_n (3). These coordination polymers are composed of primary building blocks with the general formula [Cu₂(H₄ipa-X)(L)₂]²⁺ (X = hyhb, hyhh; L = Him, Hpz) which are linked by coordination of the hydroxyl groups of the ligand side chains at the apical position of copper(II) centers of adjacent building blocks. The resulting chains possess different topologies and therefore different supramolecular structures due to the variation in length of the ligand alkyl side chains. For the complexes 1 and 2 double hydroxyalkyl-bridged distorted ladder like chains are formed. Whereas in case of complex 3 single hydroxyalkyl-bridged chains are obtained which assemble to hydrogen bonded double chains. In the case of 1 and 2 these chains are cross-linked by hydrogen bonding interactions with the perchlorate counterions, whereas for 3 additional π–π stacking interaction are observed. The temperature-dependent magnetic measurements indicate weak antiferromagnetic interactions with coupling constants J = −26.1 cm⁻¹ (1), J = −28.2 cm⁻¹ (2), and J = −26.5 cm⁻¹ (3). The magnetic exchange interaction is solely the result of a coupling within the dinuclear complex moieties through the central resorcinol moiety.     

A new water-soluble metal-free phthalocyanine substituted with naphthoxy-4-sulfonic acid sodium salt. Synthesis,aggregation, electrochemistry and in situ spectroelectrochemistry

A new water-soluble metal-free phthalocyanine, 2,9,16,23-tetrakis(4-(1-naphthoxy-4-sulfonic acid sodium salt))phthalocyanine NhtH₂Pc, where Nht indicates naphthoxy-4-sulfonic acid sodium salt, was synthesized and its aggregation, electrochemical and spectroelectrochemical properties were investigated in non-aqueous solutions. The aggregation study of NhtH₂Pc showed that NhtH₂Pc had both aggregated and non-aggregated mono phthalocyanine forms in the case of the 1:1 ratio of methanol and water, while it exhibited only the characteristic UV–Vis absorption of monomeric phthalocyanine in methanol and DMSO. NhtH₂Pc displayed three reversible one-electron reductions waves, assigned to Pc³⁻/Pc²⁻, Pc⁴⁻/Pc³⁻ and Pc⁵⁻/Pc⁴⁻ couples, respectively. The electrochemical half-wave potentials of the reduction processes were located at E_1/2 = −0.510, −0.924 and −1.24 V, respectively while the anodic potential of the oxidation process was displayed at E_1/2 = 0.590 V versus pseudo Ag/AgCl. The half-wave potentials of the first and second reductions were positively shifted by 0.150 and 0.136 V compared with those of the unsubstituted metal-free phthalocyanine (H₂Pc). These shift values are almost the same as those observed for [(SO₃)₄H₂Pc]. The electrochemical studies showed that the electron-withdrawing sulfonated-naphthoxy groups on the macrocycle core made the reduction processes of NhtH₂Pc easier in DMSO solution. The well-defined UV–Vis spectra of the electro-reduced species [NhtH₂Pc]⁻ were obtained with an applied potential (E_app = −0.70 V) in a thin-layer cell. The spectroelectrochemical results showed that the first reduction product exhibited characteristic spectral changes corresponding to mono-anionic species of metal-free phthalocyanines, having long-term stability during the reduction process.     

Selective synthesis of monomeric or dimeric titanatranes via fine tuning in triethanolateamine ligand

Monomeric titanatrane i-PrOTi(OCMe₂CH₂)₃N (1) and dimeric titanatranes [i-PrOTi(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]₂ (n = 1, 2; n = 2, 3) were synthesized by the reaction of Ti(O-i-Pr)₄ with a series of triethanolateamines such as (OCH₂CH₂)_nN(CH₂CMe₂O)_3−n³⁻ (n = 0, Lig¹; n = 1, Lig²; n = 2, Lig³), which vary by the number of CMe₂ groups adjacent to a OH functionality from 3 (Lig¹H₃) to 2 (Lig²H₃) to 1 (Lig³H₃). The resultant titanatranes 1–3 have been characterized by solution ¹H and ¹³C{¹H} NMR and their solid state structures have been determined by X-ray crystallography. Whereas compound 1 is monomeric in the solid state, compounds 2 and 3 are dimeric, due to the reduction of the steric congestion in the vicinity of the Ti.     

Synthesis, characterization and properties of some metal(II) 5-(nicotinamido)isophthalate complexes

Four new complexes, {[M(NAIP)(H₂O)₄]·2H₂O}_n (M = Co (1), M = Mn (2)), {[Zn(NAIP)]·0.5H₂O}_n (3) and {Cd(NAIP)(H₂O)₂]·1.5H₂O}_n (4) [H₂NAIP = 5-(nicotinamido)-isophthalic acid] have been prepared and structurally characterized. The ligand NAIP²⁻ exhibits different coordination modes and leads to the formation of various architectures. Complexes 1 and 2 show a one-dimensional (1D) zigzag chain, where hydrogen-bonding interactions further link these chains to a three dimensional (3D) supramolecular structure. For complex 3, a 3D coordination network with a four-coordinated Zn(II) and NAIP²⁻ as a SBU was observed. Complex 4 presents a three-connected 2-fold interpenetrated 3D network with a (10, 3)-b net topology. Their luminescent and magnetic properties have been investigated in the solid state.     

Cu acetate complexes involving N,N,O donor Schiff base ligands: Mono-atomic oxygen bridged dimers and alternating chains of the dimers and Cu2(OAc)4

Two tridentate N,N,O donor Schiff bases, HL¹ (4-(2-ethylamino-ethylimino)-pentan-2-one) and HL² (3-(2-amino-propylimino)-1-phenyl-butan-1-one) on reaction with Cu^II acetate in presence of triethyl amine yielded two basal-apical, mono-atomic acetate oxygen-bridging dimeric copper(II) complexes, [Cu₂L¹₂(OAc)₂] (1), [Cu₂L²₂(OAc)₂] (2). Whereas two other similar tridentate ligands HL³ (4-(2-amino-propylimino)-pentane-2-one) and HL⁴ (3-(2-amino-ethylimino)-1-phenyl-butan-1-one) under the same conditions produced a mixture of the corresponding dimers and a one-dimensional alternating chain of the dimer and copper acetate moiety, [Cu₄L³₂(OAc)₆]_n (3) and [Cu₄L⁴₂(OAc)₆]_n (4), formed by a very rare μ₃ bridging mode of the acetate ion. All four complexes (1–4) have been characterized by X-ray crystallography. The isotropic Hamiltonian, H = −JS₁S₂ has been used to interpret the magnetic data. Magnetic measurements of 1 and 2 in the temperature range 2–300 K reveal a very weak antiferromagnetic coupling for both complexes (J = −0.56 and −1.19 cm⁻¹ for 1 and 2, respectively).     

pH-dependent self-assembly of copper(II) complexes with a new imidazole-containing polyamine ligand: Synthesis,structure and magnetic property

Four copper(II) complexes were synthesized by reactions of new imidazole-containing polyamine ligand N¹-(2-aminoethyl)-N¹-(1H-imidazol-4-ylmethyl)-ethane-1,2-diamine (HL) with Cu(ClO₄)₂ · 6H₂O under different pH and their structures were characterized by X-ray crystallography. Interestingly, the complexes have diverse structures from protonated ligand [H₃(HL)][CuCl₄] · Cl (1), dinuclear [Cu₂(HL)₂Cl](ClO₄)₃ · H₂O (2), one-dimensional chain polynuclear {[Cu(L)](ClO₄)}_n (3) to cyclic-tetranuclear [Cu₄(L)₄](ClO₄)₄ · 3CH₃CN (4) coordination compounds by varying reaction pH from acidic to basic. The results indicate that the reaction pH has great impact on the formation and structure of the complexes. The magnetic measurements show that there are antiferromagnetic interactions between the Cu(II) centers with g = 2.09, J = −39.0 cm⁻¹ and g = 2.17, J = −36.8 cm⁻¹ for 3 and 4, respectively.     

Self-assembly of 1D coordination polymers from nickel(II) tetraaza macrocycle and carboxylate ligands

Reactions of [Ni(L)]Cl₂ · 2H₂O (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) with isophthalic acid (H₂isoph) and 1,3,5-cyclohexanetricarboxylic acid (H₃chtc) yield the 1D nickel(II) complexes {[Ni(L)(isoph)] · 3H₂O}_n (1) and {[Ni(L)(H-chtc)] · H₂O}_n (2). The structures were characterized by X-ray crystallography, spectroscopic and magnetic susceptibility. The crystal structures of the 1D chain compounds 1 and 2 show an elongated distorted octahedron about each nickel(II) ion. The magnetic behavior of two compounds exhibits weak intrachain antiferromagnetic interaction with J values of −0.93 cm⁻¹ for 1 and −1.28 cm⁻¹ for 2. The electronic spectra of the complexes are significantly affected by the nature of the carboxylate ligands.     

Synthesis,structure, and electrochemistry of pyridinecarboxamide cobalt(III) complexes; the effect of bridge substituents on the redox properties

Two series of complexes of the types trans-[Co^III(Mebpb)(amine)₂]ClO₄ {Mebpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = pyrrolidine (prldn) (1a), piperidine (pprdn) (2a), morpholine (mrpln) (3a), benzylamine (bzlan) (4a)}, and trans-[Co^III(cbpb)(amine)₂]X {cbpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-chlorobenzene dianion, and amine = pyrrolidine (prldn), X = PF₆ (1b), piperidine (pprdn), X = PF₆ (2b), morpholine (mrpln), X = ClO₄ (3b), benzylamine (bzlan), X = PF₆ (4b)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structure of 1a has been determined by X-ray diffraction. The electrochemical behavior of these complexes, with the goal of evaluating the effect of axial ligation and equatorial substitution on the redox properties, is also reported. The reduction potential of Co^III, ranging from −0.53 V for (1a) to −0.31 V for (3a) and from −0.48 V for (1b) to −0.22 V for (3b) show a relatively good correlation with the σ-donor ability of the axial ligands. The methyl and chloro substituents of the equatorial ligand have a considerable effect on the redox potentials of the central cobalt ion and the ligand-centered redox processes.     

Copper(II) complexes of symmetrical and unsymmetrical tetradentate Schiff base ligands incorporating 1-benzoylacetone: Synthesis,crystal structures and electrochemical behavior

Three new copper(II) complexes [CuL¹]₂(ClO₄)₂ (1), [CuL²]ClO₄ (2) and [CuL³] (3) with three Schiff base ligands [HL¹ = 1-phenyl-3-{3-[(pyridin-2-ylmethylene)-amino]-propylimino}-butan-1-one, HL² = 1-phenyl-3-[3-(1-pyridin-2-yl-ethylideneamino)-propylimino]-butan-1-one and H₂L³ = 3-[3-(1-methyl-3-oxo-3-phenyl-propylideneamino)-propylimino]-1-phenyl-butan-1-one] have been synthesized and structurally characterized by X-ray crystallography. The mono-negative tetradentate asymmetric Schiff base ligands (L¹)⁻ and (L²)⁻ are chelated in complexes 1 and 2 to form square planar copper(II) complexes. In complex 1, the two units are associated weakly through ketonic oxygen of benzoylacetone fragment to form the dimeric entity. The square planar geometry of complex 3 is unusually distorted towards tetrahedral one. All three complexes exhibit reversible cyclic voltammetric responses in acetonitrile solution corresponding to the Cu^II/Cu^I redox process. The E_1/2 (−0.47 V versus SCE) of 3 shows significant anodic shift due to the tetrahedral distortion around Cu(II) compare to that of 1 and 2 (−0.82 and −0.87 V versus SCE, respectively).     

Synthesis and X-ray diffraction analysis/crystal structure of new germatranes containing methyl substituents in three five-membered chelating rings

Three monomeric germatranes, 1-isopropoxy-3,3,7,7,10,10-hexamethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (1), 1-isopropoxy-3,3,7,7-tetramethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (2), and 1-isopropoxy-3,3-dimethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (3) have been synthesized by the reaction of Ge(O-i-Pr)₄ in refluxing toluene with corresponding triethanolamines, (HOCH₂CH₂)_nN(CH₂CMe₂OH)_3−n (n = 0, L1H₃; n = 1, L2H₃; n = 2, L3H₃), where the number of CMe₂ groups adjacent to a OH functionality varied from 3 (L1H₃) to 2 (L2H₃), and to 1 (L3H₃). These germatranes 1-3 have been characterized by solution ¹H and ¹³C{¹H} NMR and the solid state structure of 2 has been determined by single crystal X-ray diffraction.