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The reaction of Cu(II) salts with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-t-butylphenol (Lt-Bu-OH) afforded two bridged-phenoxido/hydroxido complexes. The dinuclear bridged acetate species [Cu2(μ-Lt-Bu-O)(μ-CH3COO)](PF6)2 (1) and the 1D polymeric doubly-bridged-chlorido {[Cu2(μ-Lt-Bu-OH)(μ-Cl)2](ClO4)2·4H2O}n (2). The two complexes were structurally characterized. Both complexes revealed ferromagnetic interactions; moderate in complex 1 (J = + 30.8 cm− 1) and very weak (J = + 2.25 cm−1) in 2.

The reaction of the polynucleating ligand 1,3,5-tris[bis(2-pyridylmethyl)aminomethyl]benzene (LTDPA) with Cu(ClO4)2 · 6H2O afforded the trinuclear complex [Cu3(TTDPA)(H2O)7](ClO4)6 · 5H2O (1). When the reaction was performed in the presence of the squarate dianion, C4O42-, the compound {[Cu6(LTDPA)2(μ1,3-C4O4)3](ClO4)6 · 12H2O}n (2) was obtained. Both compounds have been characterized by X-ray crystallography, showing a trinuclear and a 1D polymeric structures for 1 and 2, respectively. Complex 2 is composed of unusual hexametallic building blocks. Magnetic susceptibility measurements (SQUID) reveal essentially uncoupled copper(II) ions in complex 1, whereas complex 2 shows weak antiferromagnetic coupling via the squarato bridges within magnetically isolated dicopper(II) subunits of the 1D chain.

Two polynuclear Cu(II) complexes namely 1-D polymeric {[Cu(DPA)(μ1,2-C4O4)(H2O)]∙2H2O}n (1) and the tetranuclear {[Cu2(DPA)2(μ-1,1,2,3-C5O5)(H2O)](ClO4)2∙ H2O}2 (2) where DPA = bis(2-pyridylmethyl)amine, C4O42− = squarate dianion, and C5O52− = croconate dianion were synthesized and structurally characterized by X-ray crystallography. The C4O42− and C5O52− dianions are bridging the Cu2+ centers via a μ-1,2-bis(monodentate) and μ-1,2,3-bis(bidentate)-μ-1-(monodentate) bonding modes in complexes 1 and 2, respectively. A new coordination bonding mode is reported for the bridged croconate in the later complex. Hydrogen bonds stabilize the supramolecular 2D and 3D systems in the complexes. Magnetic susceptibility measurements for the 1D-polymeric complex 1 reveal insignificant coupling between the Cu(II) ions, whereas the tetranuclear croconato complex 2 exhibits moderate antiferromagnetic coupling between the central Cu(II) ions (J = − 9.4 cm–1) and weak antiferromagnetic coupling between the terminal Cu(II) ions (J = − 5.1 cm–1).

Four simultaneously different bridging coordination modes were characterized in a new 2D manganese-azide system, giving a proof of the extraordinary versatility of this ligand and the influence of the counterion in the final topology.

The reaction of an aqueous solution containing Cu(ClO4)2, N,N,N′,N″,N″-pentamethylethylene-triamine (pmedien) and 2,4-pyridine dicarboxylic acid disodium salt (Na2.2,4-pydc) afforded {[Cu3(pmedien)3(μ-2,4-pydc)(H2O)2](ClO4)4,[Cu2(pmedien)2(μ-2,4-pydc)(H2O)](ClO4)2}∙4H2O (1). The complex was structurally and magnetically characterized. Single X-ray crystallography for 1 reveals the existence of two independent molecules in the unit cell in which the dinuclear and trinuclear Cu(II) centers are bridging by the 2,4-pyridine dicarboxylato ligands. Magnetic susceptibility measurements of the complex showed that the Cu(II) ions are antiferromagnetically weakly coupled (J = − 0.27 cm−1).

The two dinuclear complexes [Cu 2 (L Me O-tmpa)(OAc) 2 ]PF 6 ·H 2 O ( 1 ) and [Cu 2 (L Me O-tmpa)(N 3 ) 2 ]ClO 4 ( 2 ), where L Me -OH-tmpa = 2,6-bis[bis(pyridine-2-ylmethyl)aminomethyl]-4-methylphenol, were synthesized and structurally and magnetically characterized. The five-coordinate geometry around the Cu(II) centers is achieved through the monodentate-acetato or -azido groups, the three N-donors of the ligand and a bridged-phenoxdio group. The two complexes reveal weak antiferromagnetic interaction.

The reaction of Cu(ClO4)2, N,N,N′,N″,N″-pentamethylethylenetriamine (pmedien) and sodium dicyanamide (Nadca) in aqueous medium led to the isolation of {[Cu(pmedien)(μ1,5-dca)]2(ClO4)2,[Cu(pmedien)(μ1,5-dca)]n(ClO4)n} (1). The complex was structurally and magnetically characterized. Single X-ray crystallography for 1 reveals the existence of two independent molecules in the unit cell: dinuclear doubly bridging complex and a 1-D polymeric chain with dca in both cases acting as a μ1,5-bridging ligand via the terminal nitrile nitrogen atoms. Magnetic susceptibility measurements of the complex showed that the Cu(II) ions are weakly coupled with ferromagnetic interaction in the dinuclear unit (Jd = 0.9 cm–1) and antiferromagnetic interaction in the polymeric chain (Jc = − 0.6 cm− 1).

The reaction of Cu(ClO4)2, 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine (DPA-CO-py) and sodium dicyanamide (Nadca) in aqueous medium led to the isolation of three complexes: {[Cu(DPA)(μ1,5-dca)]ClO4}n (1), [Cu2(pic)2(μ1,3-H2NCO–N–CN)2(H2O)2] · 2H2O (2) and Cu(pic)2 · H2O (3). The Cu2+ ion, during its complex formation with DPA-CO-py and dca not only assisted the hydrolysis of DPA-CO-py to the corresponding di(2-methylpyridyl)amine (DPA) and picolinic acid (Hpic) but also resulted in partial hydrolysis of one of the two nitrile groups of the dicyanamide, NC–N–CN− (dca) to amidocynamide, H2NCO–NH–CN. The complexes were structurally characterized and the single X-ray structures for 1 and 2 reveal their identity. Complex 1 forms a 1D polymeric chain with the dca acting as a μ1,5-bridging ligand via the terminal nitrile nitrogen atoms. A distorted SP geometry around the Cu2+ centers was achieved by the three N-atoms of the DPA and by the two nitrile groups of the bridging dca ligands. Complex 2 consists of a dimeric unit with CuN3O2 chromophore in coordination polyhedron that has a distorted SP geometry. The amidocyanamide ion, H2NCO–N–CN− acts as bis(monodentate) μ1,3-bridging ligand via the central amido and terminal nitrile nitrogen atoms whereas the picolinate anion forms a six-membered chelate ring through its pyridyl nitrogen and an oxygen atom of the carboxylate group, and the aqua water occupies the apical position of the structure. Complex 1 exhibits very weak antiferromagnetic coupling (J = −0.31 cm−1) whereas 2 shows a significant antiferromagnetic interaction between the two copper centers (J = −13.6 cm−1).

A novel 1-D coordination polymer {[Cu2(L)(μ-1,3-C4O4)(ClO4)2]·1.33 H2O}n ( C 4 O 4 2 - = 3 , 4 -dihydroxycyclobut- 3 - en - 1 , 2 -dionate , L = 1,3-bis[bis(2-pyridylmethyl)aminomethyl]benzene was synthesized and structurally characterized by X-ray crystallography. The spectral and structural characterization, electrochemical and magnetic properties as well as thermo gravimetric analyses are reported. The structure of the complex consists of the ligand L bound to two Cu(II) centers and a bridging squarato in the 1,3-bonding mode. The coordination geometry around the Cu(II) centers is a five-coordinate with a slightly distorted square pyramidal environment which is achieved by the three N-donor atoms of each arm of the ligand L, an oxygen atom of the bridging squarato moiety and by an oxygen atom of the ClO 4 - anion. The complex shows antiferromagnetic coupling between the squarato-bridged Cu(II) ions with J = −6.3 cm−1.

A novel tricopper bridged oxalato complex with the structural formula [Cu(tacp)(H2O)]2[Cu(μ2-C2O4)2(ClO4)2] (1) where tacp = 1,4,8,12-tetraazacyclopentadecane was synthesized. The complex was characterized by X-ray crystallography and by spectroscopic techniques (IR and visible). The magnetic properties were also measured at variable temperatures (300–2 K). In this compound each oxalate is acting as a bridging ligand between two Cu2+ ions, where two types of coordination modes are found for the oxalate: monodentate and bidentate fashions. The magnetic coupling between the Cu–Cu centers is very weak antiferromagnetic (the singlet–triplet energy coupling J = −0.9 cm−1) and is in full agreement with the structural results.

The complex [Cu(C10H24N4)(ClO4)]ClO4, where C10H24N4=1,4-bis(3-aminopropyl)piperazine was synthesized and characterized, and its molecular structure was established by X-ray diffraction. The complex crystallizes in orthorhombic Pbca (no. 61) with Z=8, a=14.417(3) A, b=15.067(3) A, and c=16.101(3) A. The structure consists of isolated [Cu(C10H24N4)(ClO4)]+ cations and perchlorate counter anions. The coordination geometry of the Cu(II) center may be described as square pyramidal (SP) with ClO4− group at the apical site and the N donor atoms of the neutral tetradentate ligand occupy the basal sites. The Cu–N bond distances are 2.069(4), 2.020(3) A for the internal chelate rings, and 2.033(4) and 1.996(3) A for the outer rings. The Cu–O(1) distance is 2.454(3) A. The central six-membered ring of the tetradentate ligand has a boat conformation, whereas the two terminal six-membered chelate rings of the amine ligand adopt the chair conformation.

The reaction of an aqueous solution containing Co(ClO 4 ) 2 , di(2-pyridymethyl)amine (DPA) and 3,5-pyrazole dicarboxylate anion (Hpzdc 2 − ) afforded the unprecedented diamagnetic dicobalt(III)-peroxo complex [Co 2 (DPA) 2 (μ-pzdc)(μ-η 1 :η 1 -O 2 )]ClO 4 ·3H 2 O ( 1 ) where the pyrazole group was fully deprotonated. The complex was structurally characterized by IR and UV–vis spectroscopy. X-ray crystal structure of 1 reveals the existence of the doubly bridged nature of cis -μ-η 1 :η 1 -peroxo (end-on) and the dicarboxylato pyrazole. The peroxo O–O and the Co⋯Co distances are 1.406(3) and 3.7632(5) A, respectively, and the Co(III) centers are almost co-planar with the pzdc anion.