Copper(II) complexes of ligands derived from tryptamine

Three new ligands with an indole substituent tethered to a pyridylalkylamine or imidazolylalkylamine metal-binding domain have been prepared from tryptamine. Copper(II) complexes have been prepared and characterized, three by X-ray crystallography. Electrochemistry has been used to ascertain the mutual effects of the copper and indole redox centres upon each other.     

Copper(I) and copper(II) complexes of diamino-dithioether ligands

Summary Copper(II) salts were reacted with two diamino-dithioether ligands, i.e. 1,3-di(o-aminophenylthio)propane (abbreviated H₂L¹) and 1,2-di(o-aminophenylthio)xylene (abbreviated H₂L²). Mixtures of copper(I) and copper(II) complexes were obtained with Cl^– and ClO ₄ ^– counterions. The major products were the copper(I) complexes, which were obtained pure after recrystallisation from MeCN-MeOH. The ligands lose two protons from the amine functions to form copper(I) complexes of general formula [CuL]X, where X = ClO ₄ ^– or Cl^–. The complexes were oxidised to [CuL]X₂ with H₂O₂ in DMF. Cu(NO₃)₂ on the other hand gave [CuH₂LNO₃]NO₃.     

Thermodynamic and kinetic studies on novel dinuclear platinum(II) complexes containing bidentate N,N-donor ligands

A series of novel dinuclear platinum(II) complexes were synthesized with bidentate nitrogen donor ligands. The two platinum centers are connected by an aliphatic chain of variable length. The selected chelating ligand system should stabilize the complex toward decomposition. The pK(a) values and reactivity of four synthesized complexes, viz. [Pt(2)(N(1),N(4)-bis(2-pyridylmethyl)-1,4-butanediamine)(OH(2))(4)](4+) (4NNpy), [Pt(2)(N(1),N(6)-bis(2-pyridylmethyl)-1,6-hexanediamine)(OH(2))(4)](4+) (6NNpy), [Pt(2)(N(1),N(8)-bis(2-pyridylmethyl)-1,8-octanediamine)(OH(2))(4)](4+) (8NNpy), and [Pt(2)(N(1),N(10)-bis(2-pyridylmethyl)-1,10-decanediamine)(OH(2))(4)](4+) (10NNpy), were investigated. This system is of special interest because only little is known about the substitution behavior of dinuclear platinum complexes that contain a bidentate chelate that forms part of the aliphatic bridging ligand. Spectrophotometric acid-base titrations were performed to determine the pK(a) values of the coordinated water ligands. The substitution of coordinated water by thiourea was studied under pseudofirst-order conditions as a function of nucleophile concentration, temperature, and pressure, using stopped-flow techniques and UV-vis spectroscopy. The results for the dinuclear complexes were compared to those for the corresponding mononuclear reference complex [Pt(aminomethylpyridine)(OH(2))(2)](2+) (monoNNpy), by which the effect of increasing the aliphatic chain length on the bridged complexes could be investigated. The results indicated that there is a clear interaction between the two platinum centers, which becomes weaker as the chain length between the metal centers increases. In addition, quantum chemical calculations were performed to support the interpretation and discussion of the experimental data.     

Copper(II) complexes of tridentate SNO ligands: synthesis,characterization and crystal structure

A new series of binary copper(II) complexes, [Cu(L)₂] (2) [where L is a monobasic tridentate methylthioazophenolate having NSO donor sets], has been synthesized. The reddish brown colored complexes have been characterized by elemental analyses, spectroscopic and other physico-chemical tools. The detailed structure analysis of one of the complexes, [Cu(1a)₂] (2a), by single-crystal X-ray crystallography shows that thioether-S donor center participates in coordination with the copper(II) ion with a weak interaction with long Cu–S(thioether) bond distances [2.956(2) Å and 2.925(2) Å]. Electrochemical study of the complexes in methanol using TBAP as supporting electrolyte shows that heterogeneous electron-transfer rate is low at the applied potential.     

Dinuclear zinc(II) complexes of symmetric Schiff-base ligands with extended quinoline sidearms

The synthesis of two 2-formylquinolines is reported via the Skraup method followed by SeO(2) oxidation. Each aldehyde is condensed with (1R,2R)-diaminocyclohexane and (R)-BINAM, yielding four enantiomerically-pure bis(imine-quinoline) ligands. The neutral ligands are reacted with ZnCl(2) to give complexes with bis(bidentate) coordination of ZnCl(2) units. X-Ray structural characterization of three complexes shows them to have a single-stranded helical motif, with M helicity, except in one case where a 1:1 mixture of M and P helices is seen. The ligands and complexes are further characterized spectroscopically by solution (1)H and (13)C NMR, UV-vis and ECD.     

Catechol oxidase activity of dinuclear copper(II) complexes of Robson type macrocyclic ligands: Syntheses, X-ray crystal structure, spectroscopic characterization of the adducts and kinetic studies

Five dinuclear copper(II) complexes, [Cu₂L¹(N₃)₂·2H₂O] (1), [Cu₂L²(N₃)₂·2H₂O] (2), [Cu₂L³(N₃)₂·2H₂O] (3), [Cu₂L⁴(N₃)₂·2H₂O] (4) and [Cu₂L⁵(N₃)₂·2H₂O] (5) of Robson type macrocyclic Schiff-base ligands derived from [2 + 2] condensation of 4-methyl-2,6-diformylphenol with 1,3-diaminopropane (H₂L¹), 1,2-diaminoethane (H₂L²), 1,2-diaminopropane (H₂L³), 1,2-diamino-2-methylpropane (H₂L⁴) and 1,2-diaminocyclohexane (H₂L⁵), respectively have been synthesized and characterized. Catecholase activity of those complexes using 3,5-di-tert-butylcatechol as substrate has been investigated in two solvents, methanol and acetonitrile. The role of the solvent and of the steric properties of the macrocyclic ligand of these complexes on their catecholase activity has been examined thoroughly. Acetonitrile is observed to be a better solvent than methanol as far as their catalytic activity is concerned. However, methanol reveals to be a better choice to identify the enzyme–substrate adduct. The investigation also prompted that chelate ring size does affect on the catalytic efficiency: 6-membered ring (as in H₂L¹) exhibits better activity than its 5-membered counterpart (as in H₂L²). The activity of the 5-membered counter parts also depend upon the steric factor. Moreover, the catalytic activity of the complexes is enhanced to a significant extent by increasing the bulkiness of the substituents on the backbone of macrocyclic H₂L² ligands.     

Copper(II) and nickel(II) complexes of binucleating macrocyclic bis(disulfide)tetramine ligands

Novel macrocyclic bis(disulfide)tetramine ligands and several Cu(II) and Ni(II) complexes of them with additional ligands have been synthesized by the oxidative coupling of linear tetradentate N2S2 tetramines with iodine. Facile demetalation of the Ni(II) oxidation products affords the free 20-membered macrocycles meso-9 and rac-9 and the 22-membered macrocycle 16, all of which are potentially octadentate N4S4 ligands. X-ray structure analyses reveal distinctly different conformations for the two isomers of 9; meso-9 shows a stepped conformation in profile with the disulfide groups corresponding to the rise of the step, whereas rac-9 exhibits a V conformation with the disulfide groups near the vertex of the V. No metal complexes of rac-9 have been isolated. Crystallographic studies of three Cu(II) complexes reveal that depending upon the size of the macrocyclic ligand and the nature of the additional ligands (I-, NCO-, and CH3CN), the Cu(II) coordination geometry shows considerable variation (plasticity), with substantial changes in the Cu(II)-disulfide bonding. Thus, a diiodide salt contains six-coordinate Cu(II) to which all four bridging disulfide sulfur atoms form strong equatorial bonds. In contrast, isocyanato complexes of the 20- and 22-membered macrocycles exhibit trigonal-bipyramidal Cu(II) and distorted cis-octahedral Cu(II) geometries, respectively, having only one and no short equatorially bound sulfur atoms. The coordination geometry of the latter complex can also be described as four-coordinate seesaw with two semicoordinated S(disulfide) ligands. Disulfide-->Cu(II) ligand-to-metal charge transfer absorptions of both isocyanato-containing Cu(II) species appear too weak to observe, probably because of poor overlap of the sulfur orbitals with the Cu(II) d-vacancy. The dual disulfide-bridged Ni(II) units of the crystallographically characterized octahedral Ni(II) complex of meso-9 with axial iodide and acetonitrile ligands promote substantial antiferromagnetic coupling (J = -13.0(2) cm-1).     

Pentacoordinate nickel(II) complexes double bridged by phosphate ester or phosphinate ligands: spectroscopic, structural, kinetic, and magnetic studies

The bis(phosphatediester)-bridged complexes [[Ni([12]aneN(3))(mu-O(2)P(OR)(2))](2)](PF(6))(2) [[12]aneN(3)=Me(3)[12]aneN(3), 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene; R=Me (1), Bu (2), Ph (3), Ph-4-NO(2) (4); [12]aneN(3)=Me(4)[12]aneN(3), 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene; R=Me (5), Bu (6), Ph (7), Ph-4-NO(2) (8)] were prepared by hydrolysis of the phosphate triester with the hydroxo complex [[Ni([12]aneN(3))(mu-OH)](2)](PF(6))(2) or by acid-base reaction of the dialkyl or diaryl phosphoric acid and the above hydroxo complex. The acid-base reaction was also used to synthesise the phosphinate-bridged complexes [[Ni([12]aneN(3))(mu-O(2)PR(2))](2)](PF(6))(2) [[12]aneN(3)=Me(3)[12]aneN(3), R=Me (9), Ph (10); [12]aneN(3)=Me(4)[12]aneN(3), R=Me (11), Ph (12)]. The molecular structures of complexes 2, 3 and 12 were established by single crystal X-ray diffraction studies. The eight-membered rings defined by the nickel atoms and the bridging ligands show distorted twist-boat, chair and boat-boat conformations in 2, 3 and 12, respectively. The experimental susceptibility data for compounds 2, 3 and 12 were fitted by least-squares methods to the analytical expression given by Ginsberg. The best fit was obtained with values of J=-0.11 cm(-1), D=-9.5 cm(-1) and g=2.20 for 2; J=-0.97 cm(-1), D=-9.3 cm(-1) and g=2.21 for 3; and J=-0.14 cm(-1), D=-11.9 cm(-1) and g=2.195 for 12. The magnetic-exchange pathways must involve the phosphate/phosphinate bridges, because these favour antiferromagnetic interactions. The observation of a higher exchange parameter for compound 3 is a consequence of a favourable disposition of the O-P-O bridges. The kinetics for the hydrolysis of TNP (tris(4-nitrophenyl)phosphate) with the dinuclear nickel(II) hydroxo complex [[Ni(Me(3)[12]aneN(3))(mu-OH)](2)](PF(6))(2) was studied by UV-visible spectroscopy. The proposed mechanism for TNP-promoted hydrolysis can be described as one-substrate/two-product, and can be fitted to a Michaelis-Menten equation.     

Thermal stability and kinetic studies of new dinuclear copper(II) complexes with octaazamacrocyclic and multidonor bidentate ligands

The thermal properties of four copper(II) complexes with N,N′,N″,N-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) and several bidentate ligands N,S (thiosemicarbazide and thiourea) or N,O donors (semicarbazide and urea), of the general formula [Cu₂(X)tpmc](ClO₄)₄, have been investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal stability order can be recognized for the examined complexes, depending on coordinated bidentate bridging N,S or N,O ligand. Kinetic data demonstrated first-order thermal decomposition. A plausible mechanism has been proposed which explains the major products of the degradation.     

Mono- and dinuclear nickel(II) complexes of resolved Schiff-base ligands with extended quinoline substituents

The coordination chemistry of four enantiopure tetradentate bis(iminoquinoline) ligands with nickel(II) salts is reported. The previously reported ligands CBQ, CPQ, BBQ, and BPQ result from the condensation of (1R,2R)-cyclohexyldiamine or (R)-BINAM with two equivalents of 2-formylbenzo[h]quinoline or 8-isopropyl-2-quinolinecarboxaldehyde {CBQ = (1R,2R)-cyclohexanediamine-N,N'-bis(benzo[h]quinoline-2-ylmethylene), CPQ = (1R,2R)-cyclohexanediamine-N,N'-bis[[(8-isopropyl)-2-quinolinyl]methylene], BBQ = [(R)-1,1'-binaphthalene]-2,2'-diamine-N,N'-bis(benzo[h]quinoline-2-ylmethylene), BPQ = [(R)-1,1'-binaphthalene]-2,2'-diamine-N,N'-bis[[(8-isopropyl)-2-quinolinyl]methylene]}. Reaction of NiI(2) with the (1R,2R)-cyclohexyl ligands gives the mononuclear distorted trigonal-bipyramidal (TBP) complexes [Ni(N(3)-CBQ)I(2)] and [Ni(N(3)-CPQ)I(2)]. Incomplete iodide abstraction from [Ni(N(3)-CPQ)I(2)] with AgOTf leads to partial replacement of the iodide with hydroxide from adventitious water to give [Ni(N(3)-CPQ)I(1.6)(OH)(0.4)] (distorted TBP). The corresponding reaction with [Ni(N(3)-CBQ)I(2)] again fails to remove all of the iodide, resulting instead in conversion to the syn dinuclear [Ni(2)(CBQ)(μ-X)(2)I(2)] (X = Cl(0.925)I(0.075)) complex, where chloride abstraction from the solvent (CH(2)Cl(2)) has resulted in a mixed halide system and the metal centers are square-pyramidal. Reaction of Ni(OTf)(2) with CBQ leads to the isolation of the octahedral cation [Ni(CMBQ)(2)](2+), with CMBQ [(1R,2R)-cyclohexanediamine-mono-N-(benzo[h]quinoline-2-ylmethylene)] being the partial hydrolysis product of CBQ. [Ni(CMBQ)(2)][OTf](2) crystallizes as a 1:1 mixture of P and M helical diastereomers. The coordination of NiI(2) with the (R)-BINAM derived ligands yields the anti dinuclear P-helical complexes [Ni(2)(BBQ)(μ-I)(2)I(2)] and [Ni(2)(BPQ)(μ-I)(2)I(2)]: one nickel ion is coordinated in each bidentate iminoquinoline pocket and the geometry at the metal centers is distorted square-pyramidal. Characterisation by (1)H NMR, UV-Vis, electronic circular dichroism (ECD) spectroscopy, combustion analysis, and HRMS is reported in addition to structural and halide abstraction studies.     

Copper(II) bromide complexes with acyclic and cyclic pyrimidine-containing phane ligands

Complexes of copper(II) bromide with cyclic and isostructural acyclic phane ligands containing derivatives of pyrimidine nucleobases (cytosine and uracil) were synthesized and characterized. In two cyclic pyrimidinophanes used, the macrocycles included two 6-methylthiocytosine and one 6-methyluracil units linked by polymethylene chains (L³) and two 6-methyluracil units linked by N-containing bridges (L⁵). Ligand L³ and its isostructural acyclic analogs are coordinated by the Cu²⁺ ion through the same donor sites (the ring N atoms of the thiocytosine units). The coordination polyhedra of the Cu atom in complexes with cyclic and acyclic ligands are different. Ligand L⁵ and its isostructural acyclic analog also form copper(II) complexes with different coordination polyhedra involving different donor sites. The acyclic ligand is coordinated by the Cu²⁺ ion via the bridging N atom, while cyclic ligand L⁵, via the uracil CO groups (the bridging N atoms become protonated). The resulting complexes are dielectrics.     

Copper(II)-phenylmalonate complexes with the bifunctional ligands nicotinamide and isonicotinamide

The use as coligands of the nicotinamide (nia) and isonicotinamide (inia) molecules in the complex formation between copper(II) and phenylmalonate [Phmal = dianion of phenylmalonic acid] yielded the compounds of formula [Cu(inia)(Phmal)(H₂O)] (1) and [Cu(inia)(Phmal)(H₂O)]_n (2). Although single crystals of 1 of appropriate size were grown, their unresolved twinning and space group ambiguity prevented a satisfactory X-ray structure determination. The crystal structure 2 consists of corrugated layers of copper(II) ions with intralayer carboxylate-phenylmalonate bridges in the anti-syn (equatorial-apical) coordination mode. A water molecule and the isonicotinamide group are coordinated to the copper atom in trans position being located above and below each layer. The Phmal ligand adopts the bidentate/monodentate coordination mode with the bidentate coordination involving one equatorial and one apical bonds, a feature which is unprecedented for the copper(II) complexes with alkyl(aryl)substituted-malonate derivatives. Intra- and interlayer H-bonds together with intralayer π-π type interactions between the phenyl and inia aromatic groups contribute to the stabilization of the three-dimensional supramolecular structure. Magnetic susceptibility measurements of complexes 1 and 2 in the temperature range 1.9-300 K are quasi identical and they correspond to a very weak ferromagnetic interaction between the copper(II) ions [J = +0.091(2) cm⁻¹ (1) and +0.097(2) cm⁻¹ (2) through the spin Hamiltonian for an isotropic square grid of interacting spin doublets which is defined as H = −JΣ_iS_i · S_i+1]. The strong similarity in the magnetic properties of 1 and 2 allow us to conclude that although they are not isostructural species, their structures have to be very close.     

Copper(II) complexes bearing cyclobutanecarboxylate and pyridine ligands: a new series of dinuclear paddle-wheel complexes

Monatshefte für Chemie - Chemical Monthly - Four members of a new series of paddle-wheel copper(II) complexes bearing cyclobutanecarboxylate as bridging ligand with pyridine derived ligands in...     

Tellurium(II) and tellurium(IV) complexes of phosphine chalcogenide ligands,synthesis and X-ray structures

Reaction of TeX₄ (X = Cl or Br) with 2 mol. equiv. of OPR₃ (R = Me, Et or Ph) gives the distorted octahedral cis-[TeX₄(OPR₃)₂], while the bidentates Ph₂P(E)(CH₂)_nP(E)Ph₂ (E = O, n = 1 or 2; E = S, n = 1) give the six-coordinate [TeX₄{Ph₂P(E)(CH₂)_nP(E)Ph₂}]. These species have been characterised spectroscopically (via ¹H and ³¹P{¹H} NMR and IR) and by crystallographic analyses on cis-[TeBr₄(OPPh₃)₂], [TeCl₄{Ph₂P(O)CH₂P(O)Ph₂}] and [TeBr₄{Ph₂P(S)CH₂P(S)Ph₂}]. The TeX₄ (X = Cl or Br) are reduced by Ph₂P(S)(CH₂)₂P(S)Ph₂ and Ph₂P(Se)CH₂P(Se)Ph₂, giving the planar, four-coordinate Te(II) species [Te{Ph₂P(S)(CH₂)₂P(S)Ph₂}₂]²⁺ (isolated as [(TeCl₅)₂{μ-Ph₂P(S)(CH₂)₂P(S)Ph₂}]^2? and [TeBr₆]^2? salts) and [TeBr₂{Ph₂P(Se)CH₂P(Se)Ph₂}], all of which have also been identified crystallographically. On the basis of the structural data the Te-based lone pair associated with the Te(IV) species is assumed to occupy the 5s orbital, whereas in the Te(II) complexes the planar coordination is consistent with the two stereochemically active lone pairs occupying the axial sites.     

Copper(II) complexes of new biomimetic polydentate amide ligands: a spectroscopic study

Complexes of Cu(II) with N,N'-bis(3-carboxy-1-oxopropanyl)-1,2-ethylenediamine(C(10)H(16)N(2)O(6),L(1)), N,N'-bis(3-carboxy-1-oxopropanyl)-1,2-phenylenediamine(C(14)H(16)N(2)O(6),L(2)), N,N'-bis(2-carboxy-1-oxophenelenyl)-1,2-phenylenediamine(C(22)H(16)N(2)O(6),L(3)) and N,N'-bis(3-carboxy-1-oxoprop-2-enyl)-1,2-phenylenediamine(C(14)H(12)N(2)O(6),L(4)) have been prepared and characterised by elemental analyses, vibrational spectra, magnetic susceptibility measurements, ligand field spectra, EPR spectra, thermal studies and X-ray diffraction spectra. Vibrational spectra indicate coordination of amide and carboxylate oxygens of the ligands giving a MO(4) square planar chromophore. Ligand field and EPR spectra support square planar geometry around Cu(II). [Cu(L(1))] complex has the maximum activation energy and [Cu(L(3))] complex has the minimum activation energy.     

The electronic effect of quinoline moieties on the lability of platinum(II) complexes of tridentate N^N^N and N^C^N ligands: a kinetic,mechanistic and theoretical analysis

Transition Metal Chemistry - The rate of the chloride ligand displacement by three thiourea neutral nucleophiles (Nu) of different steric demands, namely thiourea (Tu), N,N’-dimethylthiourea...     

Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses,structural characterization and magnetic properties

Two new methylmalonate-bridged copper(II) complexes with the formulas [Cu(3-Ipy)(Memal)(H₂O)] (1) and [Cu(2,4′-bpy)(Memal)(H₂O)] · 3H₂O (2) [Memal = methylmalonate dianion, 3-Ipy = 3-iodopyridine, 2,4′-bpy = 2,4′-bipyridine] have been synthesized and characterized by X-ray diffraction. Both compounds crystallize in the monoclinic space group P2₁/n and Z = 4, with unit cell parameters a = 8.5874(13) Å, b = 7.1738(14) Å, c = 19.093(5) Å, β = 99.509(15)° in 1 and a = 17.375(4) Å, b = 7.3305(14) Å, c = 14.247(3) Å, β = 111.409(15)° in 2. The structures of 1 and 2 consist of zigzag chains of anti-syn carboxylate-bridged copper(II) ions running along the b direction. The pyridine-like ligands occupy one equatorial position of the copper environment avoiding the formation of the sheet-like arrangement observed in previously reported Memal complexes. The chains are grouped together in hydrophilic layers through hydrogen bonds and the layers are pillared through the 3-Ipy (1) and 2,4′-bpy (2) ligands which are stacked through π–π interactions involving alternatively aromatic ligands from two adjacent chains. Magnetic susceptibility measurements of both compounds in the temperature range 2–290 K show the occurrence of intrachain ferromagnetic interactions between the copper(II) ions [J = +2.66(2) cm^?1 (1) and J = +2.62(2) cm^?1 (2)].     

Copper(I) and copper(II) complexes possessing cross-linked imidazole-phenol ligands: structures and dioxygen reactivity

Catalytic reduction of O2 to H2O, and coupling to membrane proton translocation, occurs at the heterobinuclear heme a3-CuB active site of cytochrome c oxidase. One of the CuB ligated histidines is cross-linked to a neighboring tyrosine (C-N bond; tyrosine C6 and histidine epsilon-nitrogen), and the protic residue of this cross-linked His-Tyr moiety is proposed to participate as both an electron and a proton donor in the catalytic dioxygen reduction event. To provide insight into the chemistry of such a moiety, we have synthesized and characterized tetra- and tridentate pyridylalkylamine chelate ligands {LN4OR and LN3OR (R = H or Me)}, which include an imidazole-phenol (or anisole) cross-link and their copper(I/II) complexes. [CuI(LN4OH)]B(C6F5)4 (1) reacts with dioxygen at -80 degrees C in THF, forming an unstable trans-mu-1,2-peroxodicopper(II)complex, which subsequently converts to a dimeric copper(II)-phenolate complex [{Cu(LN4O-)}2](B(C6F5)4)2 (5a). The close analogue [CuI(LN4OMe)]B(C6F5)4 (3) binds dioxygen reversibly at -80 degrees C in tetrahydrofuran. Stopped-flow kinetics of the reaction [CuI(LN3OH)]ClO4 (2) with O2 in CH2Cl2 indicate a steady formation of the purple dimeric product [{Cu(LN3O-)}2](ClO4)2 (5b), which has been analyzed in the temperature range from -40 to +20 degrees C, DeltaH = -9.6 (6) kJ mol-1, DeltaS = -168 (2) J mol-1 K-1 (k(-40 degrees C) = 1.05(4) x 106 and k(+20 degrees C) = 4.6(2) x 105 M-2 s-1). The X-ray crystal structures of 1, [CuII(LN3OH)(MeOH)(OClO3-)](ClO4) (4), 5a, and 5b are reported.     

Copper(II) azide complexes with mono-anionic tridentate Schiff-base ligands: monomer versus dimer

Three new copper(II) complexes [CuL¹N₃]₂ (1), [CuL²N₃] (2) and [CuL³N₃] (3) with three very similar tridentate Schiff base ligands [HL¹?=?6-diethylamino-3-methyl-1-phenyl-4-azahex-3-en-1-one, HL²?=?6-amino-3-methyl-1-phenyl-4-azahex-3-en-1-one and HL³?=?6-amino-3-methyl-1-phenyl-4-azasept-3-en-1-one] have been synthesized and structurally characterized by X-ray crystallography. In complex 1 half of the molecules are basal-apical, end-on azido bridged dimers and the remaining half are square-planar monomers whereas all the molecules in complexes 2 and 3 are monomers with square-planar geometry around Cu(II). A competition between the coordinate bond and H-bond seems to be responsible for the difference in structure of the complexes.