Palladium(II) derivatives of alkylsulfanyl substituted thiophenes as precursors of inorganic polymers: Spectroscopic, electrochemical investigations and X-ray crystal structure of trans-PdCl2[3-(butylsulfanyl)thiophene]2

Palladium(II) complexes with two thiophene derivatives bearing alkylsulfanyl chains, i.e., 3-(n-butylsulfanyl)thiophene and 4,4′-bis(n-butylsulfanyl)-2,2′-bithiophene, are synthesised and spectroscopically and electrochemically characterised. The molecular structure of PdCl₂[3-(n-butylsulfanyl)thiophene]₂ was determined by X-ray analysis. The properties of the complexes have been compared with those of PdCl₂[3,3′-bis(n-butylsulfanyl)-2,2′-bithiophene] and of a conductive polymer partially coordinated with Pd(II), previously synthesised by us. We found that Pd(II) ions can coordinate sulfanyl sulfur atoms both in cis and trans configuration, leading to a reticulate material, where some kind of interchain bridging may be reasonably supposed to enhance the bulk conductivity.     

A solution thermodynamic study of the Cu(II) and Zn(II) complexes of EBTA: X-ray crystal structure of the dimeric complex [Cu2(EBTA)(H2O)3]2

The copper(II) complex of the acyclic EBTA ligand (H₄EBTA = 1,2-bis(2-aminoethoxy)benzene-N,N,N′,N′-tetraacetic acid) has been prepared and characterized by X-ray analysis. The two copper ions of the dinuclear unit present the same distorted octahedral coordination polyhedra. The EBTA ligand is shared between two copper coordination centres, with the formation of centrosymmetric dimers, which are linked in a supramolecular tridimensional structure via additional interactions through the coordinated waters molecules with adjacent carboxylic oxygen atoms. The stability and protonation constants of EBTA with Cu(II) and Zn(II) ions indicate a higher stability of these complexes with respect to the corresponding complexes with the more flexible EGTA ligand (H₄EGTA = ethyleneglycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid). On the other hand, the lower stability of [Gd(EBTA)]⁻ than [Gd(EGTA)]⁻ results in a decreased overall selectivity (lower K_sel) of EBTA towards Gd(III) and suggests that this complex may undergoes transmetallation reactions under physiological conditions.     

Spin-crossover iron(II) complexes [Fe(Medpq)(py)2(NCS)2] and [Fe(Medpq)(py)2(NCSe)2]: syntheses, characterization and magnetic properties

Two new spin-crossover complexes, [Fe(Medpq)(py)₂(NCS)₂] · py · 0.5H₂O (1) and [Fe(Medpq)(py)₂(NCSe)₂] · py (2) (Medpq = 2-methyldipyrido[3,2-f:2′,3′-h]-quinoxaline, py = pyridine), have been synthesized. The crystal structures were determined at both room temperature (298 K) and low temperature (110 K). Complexes 1 and 2 crystallize in the orthorhombic space group Pbca and monoclinic space group P2₁/n, respectively. In both complexes, the distorted [FeN₆] octahedron is formed by six nitrogen atoms from Medpq, the trans pyridine molecules and the cis NCX⁻ groups. The thermal spin transition is accompanied by the shortening of the mean Fe–N distances by 0.194 Å for 2. The mononuclear [Fe(Medpq)(py)₂(NCS)₂] and [Fe(Medpq)(py)₂(NCSe)₂] neutral species interact each other via π-stacking, resulting in a one-dimensional extended structure for both 1 and 2. There exist C–HX (X = S, Se) hydrogen bonds for both complexes. Variable-temperature magnetic susceptibility measurements and Mössbauer spectroscopy reveal the occurrence of a gradual spin transition. The transitions are centered at T_1/2 = 120 K for 1 and T_1/2 = 180 K for 2, respectively.     

Synthesis and characterization of Pd(II) and Pt(II) complexes with triazolopyrimidine derivatives: The crystal structure of [Pd2L2Cl4] where L = 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine

The Pd(II) and Pt(II) complexes with triazolopyrimidine C-nucleosides L¹ (5,7-dimethyl-3-(2′,3′,5′-tri-O-benzoyl-β-d-ribofuranosyl-s-triazolo)[4,3-a]pyrimidine), L² (5,7-dimethyl-3-β-d-ribofuranosyl-s-triazolo[4,3-a]pyrimidine) and L³ (5,7-dimethyl[1,5-a]-s-triazolopyrimidine), [Pd(en)(L¹)](NO₃)₂, [Pd(bpy)(L¹)](NO₃)₂, cis-Pd(L³)₂Cl₂, [Pd₂(L³)₂Cl₄] · H₂O, cis-Pd(L²)₂Cl₂ and [Pt₃(L¹)₂Cl₆] were synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of the [Pd₂(L³)₂Cl₄] · H₂O complex was established by X-ray crystallography. The two L³ ligands are found in a head to tail orientation, with a Pd?Pd distance of 3.1254(17) Å. L¹ coordinates to Pd(II) through N8 and N1 forming polymeric structures. L² coordinates to Pd(II) through N8 in acidic solutions (0.1 M HCl) forming complexes of cis-geometry. The Pd(II) coordination to L² does not affect the sugar conformation probably due to the high stability of the C-C glycoside bond.     

The structure of the dichromium compound Cr2(μ-OH)2(μ-3,5Cl2-form)2(η-3,5Cl2-form)2

With exposure to trace amounts of air and moisture, the Cr₂(II, II) complex Cr₂(μ-3,5Cl₂-form)₄, where 3,5Cl₂-form is [(3,5-Cl₂C₆H₃)NC(H)N(3,5-Cl₂C₆H₃)⁻], undergoes an oxidative addition reaction. Structural information from the X-ray crystal structure of the edge-sharing bioctahedral (ESBO) Cr₂(III, III) product Cr₂(μ-OH)₂(μ-3,5Cl₂-form)₂(η²-3,5Cl₂-form)₂ (1) indicates 1 has a significantly longer Cr–Cr distance [2.732(2) Å] than Cr₂(μ-3,5Cl₂-form)₄ [1.9162(10) Å], but the shortest Cr–Cr distance in an ESBO Cr₂(III, III) complex recorded to date.     

Iodo bridged lead(II) compounds of azoimidazoles: Single crystal X-ray structures of [di-iodo-{1-methyl-2-(p-tolylazo)imidazole}lead(II)]n and {1-methyl-3-benzyl-2-(p-tolylazo)imidazolium}m-{tri-iodoplumbate(II)}m

PbI₂ forms iodo-bridged neutral polymer upon reaction with 1-alkyl-2-(arylazo)imidazoles (RaaiR′). The reaction of PbI₂ and dialkyl imidazolium iodides [RaaiR′R″]⁺I⁻ has synthesized {1,3-dialkyl-2-(arylazo)imidazolium}_m-{tri-iodoplumbate(II)}_m. The complexes are characterized by different spectroscopic studies. Iodobridged chelated polymer, [Pb(RaaiR′)I₂]_n, has been established by single crystal X-ray diffraction measurements in one case. Tri-iodoplumbates form iodo bridged anion polymer, which connects [RaaiR′R″]⁺ by hydrogen bonding and are placed in between the pillars of [Pb(μ-I)₆]_n motif.     

A novel ferromagnetic coupling one-dimensional complex {Cu(II)(NIT3Py)2[N(CN)2]2(H2O)2}

The novel ferromagnetic coupling one-dimensional complex {Cu(NIT3Py)₂[N(CN)₂]₂(H₂O)₂} (NIT3Py=2-(3^′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was synthesized and characterized structurally and magnetically. It crystallizes in the monoclinic space group C2/c. The Cu(II) ion is in a distorted octahedral environment. The units of {Cu(NIT3Py)₂[N(CN)₂]₂(H₂O)₂} were connected as one-dimensional structure by the intermolecular hydrogen bonds. Magnetic measurements show that there are intramolecular ferromagnetic interactions and intermolecular antiferromagnetic interactions within the chain.     

Synthesis, crystal structure and magnetic properties of the first structurally characterized 1,2-dithiocroconato-containing Cu(II) complex, [Cu(bpca)(H2O)]2[Cu(1,2-dtcr)2]·2H2O

The first crystal and molecular structure of a transition metal complex containing 1,2-dithiocroconate (1,2-dtcr, dianion of 1,2-dimercaptocylopent-1-ene-3,4,5-trione), [Cu(bpca)(H₂O)]₂[Cu(1,2-dtcr)₂]·2H₂O (where bpca is the bis(2-pyrdidylcarbonyl)amide anion), has been determined by single crystal X-ray diffraction methods. The compound crystallizesin the monoclinic syste, space group P2₁/c, with a = 11.661(3), b = 20.255(6), c = 8.265(3) Å, ß = 107.26(2)° and Z = 2. The structure is formally built of [Cu(1,2-dtcr)₂]²⁻ and [Cu(bpca)(H₂O)]⁺ ions and water of hydration. The copper atom of the anion is situated at a crystallographic inversion centre, bonded to four sulfur atoms in a planar, approximately square arrangement. In the cation the copper equatorial plane is formed by the three nitrogen atoms of the bpca ligand and a water oxygen atom. In addition there is a very weak axial bond to one of the sulfur atoms of a 1,2-dtcr ligand in the anion. Through these latter weak bonds each anion is connected to, and sandwiched between, two cations, resulting in neutral, trinuclear, centrosymmetric formula units. The triple-decker molecules are arranged in stacks along the crystallographic a-axis creating close contacts between the terminal copper atoms and bpca groups of the neighbouring molecules. This intermolecular interaction is, however, too weak to define the structure as a chain compound. The distance between adjacent copper atoms within the trinuclear unit is 4.189(1) Å, while the shortest intra-stack metal-metal separation between terminal copper atoms is 5.281(1) Å. Variable-temperature magnetic susceptibility measurements in the temperature r.2–140 K reveal that a Curie law is followed; with three non-interacting copper(II) ions in the formula unit.     

Rhenium(IV) cyanate complexes: Synthesis, crystal structures and magnetic properties of NBu4[ReBr4(OCN)(DMF)] and (NBu4)2[ReBr(OCN)2(NCO)3]

Two new rhenium(IV) mononuclear compounds of formula NBu₄[ReBr₄(OCN)(DMF)] (1) and (NBu₄)₂[ReBr(OCN)₂(NCO)₃] (2) (NBu₄ = tetrabutylammonium cation, OCN = O-bonded cyanate anion, NCO = N-bonded cyanate anion and DMF = N,N-dimethylformamide) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 crystallizes in the monoclinic system with the space group P2₁/n, whereas 2 crystallizes in the triclinic one with as space group. In both complexes the rhenium atom is six-coordinated, in 1 by four Br atoms in the equatorial plane, and two trans-oxygen atoms, one of a DMF molecule and another one from a cyanato group, while in 2 by one bromide anion and five cyanate ligands, two of which are O-bonded and three N-bonded, forming a somewhat distorted octahedral surrounding. Magnetic susceptibility measurements on polycrystalline samples of 1 and 2 in the temperature range 1.9-300 K are interpreted in terms of magnetically isolated spin quartets with large values of the zero-field splitting (|2D| is ca. 41.6 and 39.2 cm⁻¹ for 1 and 2, respectively).     

Syntheses, characterization and antimicrobial activity of the first complexes of Zn(II), Cd(II) and Co(II) with N-benzyloxycarbonylglycine: X-ray crystal structure of the polymeric Cd(II) complex

For the first time, complexes of Zn(II), Cd(II) and Co(II) (1-3) with N-benzyloxycarbonylglycine have been synthesized and characterized. The complexes adopt tetrahedral, pentagonal-bipyramidal and octahedral geometry, respectively. The structure of the polymeric cadmium complex was resolved by single crystal X-ray analysis. The cadmium ion has a distorted pentagonal-bipyramidal coordination formed by two water molecules and two N-benzyloxycarbonylglycinato ligands (N-Boc) coordinated in different fashions, one as bidentate and the second connecting three cadmium atoms. In a rather complicated 2D supramolecular structure, the phenyl rings interact mutually exclusively by the CH?π interactions.Investigation of the antimicrobial activity of the obtained complexes and N-benzyloxycarbonylglycine revealed that the ligand does not inhibit the growth of Candida albicans, whereas the newly synthesized complexes suppress the growth of this human fungal pathogen.     

Preparation and crystal structure of two novel cadmium (II)-trimesates, Cd(HTMA)(NC5H5)2 · 0.5CH3OH · 0.5DMF and Cd(HTMA) · 2H2O

Two novel complexes, Cd(HTMA)(NC₅H₅)₂ · 0.5CH₃OH · 0.5DMF (1) and Cd(HTMA) · 2H₂O (2), of cadmium (II)-trimesates are obtained from slow vapor diffusion and urea hydrolysis, respectively. The Cd(II) centers in the two complexes are bridged by three separate HTMA³⁻ ligands using a same coordination fashion, which contains one monodentate and two chelating bidentate carboxyl groups to form the herringbone-like motif. The herringbone-like motif is further interlinked to construct the two-dimensional Cd(II)-HTMA layer, which is stacked by mutual π-stacking of pyridines for 1 and by hydrogen bond of waters for 2. Thermal stabilities of the two complexes were investigated and the results indicated that Cd(II)-TMA layers in the two complexes are stable still upon 190 °C.     

Synthesis and characterization of the first zinc(II) complexes involving kinetin and its derivatives: X-ray structures of 2-chloro-N6-furfuryl-9-isopropyladenine and [Zn(kinetin)2Cl2]·CH3OH

A series of the first zinc(II) complexes of the general composition [Zn(Lⁿ)₂Cl₂]·xSolv (1-5) involving kinetin [N6-furfuryladenine, L¹, xSolv = CH₃OH, complex 1] and its derivatives, i.e. N6-(5-methylfurfuryl)adenine (L², xSolv = 2H₂O, 2), 2-chloro-N6-furfuryladenine (L³, 3), 2-chloro-N6-(5-methylfurfuryl)adenine (L⁴, 4) and 2-chloro-N6-furfuryl-9-isopropyladenine (L⁵, 5), as N-donor ligands has been synthesized. The complexes have been fully characterized by elemental analyses (C, H, N), FTIR, Raman, ¹H and ¹³C NMR spectroscopy, conductivity measurements, thermogravimetric (TG) and differential thermal (DTA) analyses. Single crystal X-ray analysis determined the molecular structures of 2-chloro-N6-furfuryl-9-isopropyladenine (L⁵) and the complex [Zn(L¹)₂Cl₂]·CH₃OH. The Zn(II) ion is tetrahedrally coordinated by two chlorido ligands and two molecules of the L¹ organic compound. The two ligands L¹ are coordinated to the central Zn(II) ion via the N7 atoms. This conclusion can also be drawn from multinuclear NMR spectroscopic experiments.     

Mn(II) complexes of monoanionic bidentate chelators: X-ray crystal structures of Mn(dha)2(CH3OH)2 (Hdha = dehydroacetic acid) and [Mn(ema)2(H2O)]2 · 2H2O (Hema = 2-ethyl-3-hydroxy-4-pyrone)

This report describes synthesis and characterization of bis-ligand Mn(II) complexes of bidentate chelators: maltol (3-hydroxy-2-methyl-4-pyrone), ethylmaltol (2-ethyl-3-hydroxy-4-pyrone), 1,2-dimethyl-3-hydroxy-4-pyridinone (DMHP) and dehydroacetic acid. All four Mn(II) complexes were characterized by elemental analysis, IR, UV/Vis, EPR, cyclic voltammetry, and X-ray crystallography in cases of Mn(dha)₂(CH₃OH)₂ and [Mn(ema)₂(H₂O)]₂ · 2H₂O. The bidentate chelator plays a significant role in the solid state structure of its Mn(II) complex. For example, dha forms the monomeric complex Mn(dha)₂(CH₃OH)₂ while ethylmaltol forms the dimeric complex [Mn(ema)₂(H₂O)]₂. Because of smaller size, maltol ligands in Mn(ma)₂ are able to bridge adjacent Mn(II) centers to give a polymeric structure in solid state. Despite of the difference in their solid state structures, both Mn(ema)₂ and Mn(ma)₂ exist in solution as monomeric Mn(II) species, Mn(ema)₂(H₂O)₂ and Mn(ma)₂(H₂O)₂. This assumption is supported by the similarity in their UV/Vis spectra, EPR data and electrochemical properties. Replacing maltol with DMHP results in a decrease (by ∼100 mV) in the redox potential for the Mn(II)/Mn(III) couple, suggesting that DMHP stabilizes Mn(III) better than maltol. Since Mn(DMHP)₂(H₂O)₂ is readily oxidized to form the more stable Mn(III) complex Mn(DMHP)₃, DMHP has the potential as a chelator for removal of excess Mn(II) from patients with chronic Mn toxicity.     

Transition metal complexes of 2-amino-3,5-dihalopyridines: Synthesis, structures and magnetic properties of Cu(3,5-diCAP)2X2 and Cu(3,5-diBAP)2X2

A family of bis(2-amino-3,5-dihalopyridine)dihalocopper(II) compounds has been synthesized, including (3,5-diCAP)₂CuCl₂ (1), (3,5-diCAP)₂CuBr₂ (2), (3,5-diBAP)₂CuCl₂ (3), and (3,5-diBAP)₂CuBr₂ (4) [3,5-diCAP = 2-amino-3,5-dichloropyridine; 3,5-diBAP = 2-amino-3,5-dibromopyridine]. These complexes have been analyzed through single crystal X-ray diffraction and temperature dependant magnetic susceptibility. The compounds are all isostructural, forming bi-bridged chains with long Cu-X?Cu bridges in the crystal lattice. The two copper chloride compounds (1 and 3) exhibit weak antiferromagnetic interactions along these chains.     

Benzylamidine complexes of platinum(II) derived by nucleophilic addition of primary and secondary amines. X-ray crystal structure of trans-[PtCl2{Z-N(H)C(NHMe)CH2Ph}2]

The reaction of cis- and trans-[PtCl₂(NCCH₂Ph)₂] with a 5-fold excess of MeNH₂ and Me₂NH in CH₂Cl₂ at −10 °C affords in high yield the bis-amidine derivatives cis- and trans-[PtCl₂{Z-N(H)C(NHMe)CH₂Ph}₂] (1a, 2a) and cis- and trans-[PtCl₂{E-N(H)C(NMe₂)CH₂Ph}₂] (3a, 4a), respectively. The complexes were characterized by means of elemental analysis, multinuclear NMR and FT-IR techniques. The X-ray diffraction analysis was carried out for trans-[PtCl₂{Z-N(H)C(NHMe)CH₂Ph}₂] (2a).Moreover, the in vitro cytotoxicity for the new derivatives was evaluated in a wide panel of human tumor cell lines.     

Coordination chemistry of acrylamide 3: Synthesis, crystal structure and IR spectroscopic properties of dichloro-tetrakis(O-acrylamide)copper(II), [Cu(O-OC(NH2)CHCH2)4Cl2]

The molecular structure of copper(II) chloride complex with acrylamide (AAmCH₂CHCONH₂), [Cu(AAm)₄Cl₂], was determined using X-ray diffraction analysis. The complex crystallizes in the cubic space group I-43d with a = 17. 8310(2) Å, β = 90°, and V = 5669.27(11) ų for Z = 12. The acrylamide molecules bind to the metal center via the carbonyl oxygen atom (Cu-O 1.996 Å). The coordination geometry of the metal center in the complex involves a tetragonally distorted octahedral structure with four O-donor atoms of acrylamide bonded in the equatorial positions and two chlorides in the apical positions. Comparison of crystal structure data of acrylamide and metal acrylamide complexes of those formed with divalent transition metal chlorides has been summarized.     

Mg-activated double-stranded DNA cleavage by [(bpy)2(OH2)Ru---O---Ru(H2O) (bpy)2]

The reaction of the title complex with DNA has been examined. Addition of [(bpy)₂(OH₂)RuORu(OH₂) (bpy)₂]⁴⁺ to DNA leads to the reduction of the complex to Ru(bpy)₂(OH₂)₂²⁺, as indicated by absorption spectroscopy and cyclic voltammetry. The reaction is accelerated by Mg²⁺. The combined evidence points to a mechanism where the oxo-bridged dimer is hydrolyzed to a monomeric Ru(III) complex that is capable of oxidizing DNA to effect strand scission. Gel electrophoresis demonstrates nicking of supercoiled /gfX174 DNA by [(bpy)₂(OH₂)RuORu(OH₂) (bpy)₂]⁴⁺, and double-stranded cleavage is observed in the presence of Mg²⁺. Linearization of the plasmid prior to treatment with the complex does not lead to further fragmentation, suggesting that supercoiling is required to realize double-stranded cleavage.     

Synthesis and crystal structure of the low-spin iron(II) complex [Fe(bpz)3](ClO4)2 · H2O (bpz=2,2-bipyrazine)

The crystal structure of the title compound [Fe(bpz)₃](ClO₄)₂ · H₂O (bpz=2,2^′-bipyrazine) has been determined by a single crystal X-ray diffraction study at 293(2) K. The complex is monoclinic, P2₁/c, a=17.263(3), b=9.983(2), c=17.921(4) Å, β=107.94(3)°, V=2938.3(10) ų, Z=4, R=0.073 and R_w=0.118. The structure is made up of tris-chelated [Fe(bpz)₃]²⁺ cations, uncoordinated perchlorate anions and crystallization water molecules. The iron atom exhibits a FeN₆ distorted octahedral geometry with average Fe-N bond length and N-Fe-N bidentate angle of 1.962(5) Å and 81.6(2)°. The value of the Fe-N bond distance and that of the room temperature magnetic moment are in agreement with a singlet ¹A₁ ground state. The structure of 1 is compared to those of other tris-chelated iron(II) complexes with bidentate nitrogen heterocycles.     

Synthesis, spectroscopy and thermal behavior of new lead(II) complexes derived from S-methyl/benzyldithiocarbazates (SMDTC/SBDTC): X-ray crystal structure of [Pb(SMDTC)(NO3)2]

Lead(II) complexes of S-methyldithiocarbazate (SMDTC), [Pb(SMDTC)(NO₃)₂] (1) and S-benzyldithiocarbazate (SBDTC), [Pb(SBDTC)(NO₃)₂] (2) have been synthesized for the first time and characterized by elemental analysis, IR and TGA techniques. The complexes were obtained by addition of the appropriate ligand to an aqueous ethanolic solution of lead(II) nitrate in 1:1 molar ratio. The X-ray crystal structure of complex 1 has been determined by single crystal X-ray diffractometry. In complex 1, lead(II) is in a nine coordinated sphere with seven oxygen atoms of the nitrate groups and thione sulfur, β-nitrogen of neutral bidentate NS chelating ligand. Three nitrate groups act as bidentate chelating whereas the fourth nitrate group is coordinating to the central lead(II) and at the same time it bridges with neighboring lead(II) atom. Coordination geometry of the central lead(II) atom has a tricapped trigonal prismatic arrangement with streochemically inactive lone pair. The lead atoms are linked into polymeric chains and these chains form twin polymeric ribbons linked through bridging oxygen atoms. The N-H?O hydrogen bond network between N_SMDTC and O_nitrate atom leads to self-assembled molecular conformation and stabilizes the crystal structure. The complex 2 with similar spectral and thermal behavior is expected to have a tricapped trigonal prismatic structure. The thermal behavior studies shows that the complexes start to decompose at relatively low temperature (ca. 110 °C) to give PbS residue.     

Structural analysis and magnetic properties of the copper(II) dicyanamide complexes [Cu2(dmphen)2(dca)4], [Cu(dmphen)(dca)(NO3)]n and [Cu(4,4-dmbpy)(H2O)(dca)2] (dca=dicyanamide; dmphen=2,9-dimethyl-1,10-phenanthroline; 4,4-dmbpy=4,4-dimethyl-2,2-bipyridine)

The preparation, crystal structures and magnetic properties of three copper(II) compounds of formulae [Cu₂(dmphen)₂(dca)₄] (1), [Cu(dmphen)(dca)(NO₃)]_n (2) and [Cu(4,4^′-dmbpy)(H₂O)(dca)₂] (3) (dmphen=2,9-dimethyl-1,10-phenanthroline, dca=dicyanamide and 4,4^′-dmbpy=4,4^′-dimethyl-2,2^′-bipyridine) are reported. The structure of 1 consists of discrete copper(II) dinuclear units with double end-to-end dca bridges whereas that of 2 is made up of neutral uniform copper(II) chains with a single symmetrical end-to-end dca bridge. Each copper atom in 1 and 2 is in a distorted square pyramidal environment: two (1) or one (2) nitrile-nitrogen atoms from bridging dca groups, one of the nitrogen atoms of the dmphen molecule (1 and 2) and either one nitrile-nitrogen from a terminal dca ligand (1) or a nitrate-oxygen atom (2) build the equatorial plane whereas the second nitrogen atom of the heterocyclic dmphen fills the axial position (1 and 2). The copper-copper separations through double (1) and single (2) end-to-end dca bridges are 7.1337(7) (1) and 7.6617(7) (2). Compound 3 is a mononuclear copper(II) complex whose structure contains two neutral and crystallographically independent [Cu(4,4^′-dmbpy)(H₂O)(dca)₂] molecules which are packed in two different layer arrangements running parallel to the bc-plane and alternating along the a-axis. The copper atoms in both molecules have slightly distorted square pyramidal surroundings with the two nitrogen atoms of the 4,4^′-dmbpy ligand and two dca nitrile-nitrogen atoms in the basal plane and a water oxygen in the apical position. A semi co-ordinated dca nitrile-nitrogen from a neighbour unit [2.952(6) Å for Cu(2)-N] is in trans position to the apical water molecule in one of the two molecules, this feature representing part of the difference in supramolecular connections in the alternating layers referred to above. Magnetic susceptibility measurements for 1-3 in the temperature range 1.9-290 K reveal the occurrence of weak antiferromagnetic interactions through double [J=−3.3 cm⁻¹ (1), ] and single [J=−0.57 cm⁻¹ (2), ] dca bridges and across intermolecular contacts [θ=−0.07 K (3)].