Non-coordinated Water Molecules Research Articles

Iron(II) Spin‐Transition Complexes with Dendritic Ligands, Part II

AbstractThe dendritic triazole‐based complexes [Fe(G1‐BOC)3](triflate)2·xH2O (1; G1‐BOC = tert‐butyl {3‐[3‐(3‐tert‐butoxycarbonylaminopropyl)‐5‐([1,2,4]triazol‐4‐ylcarbamoyl)phenyl]propyl}carbamate, triflate = CF3SO3–), [Fe(G1‐BOC)3](tosylate)2·xH2O (2; tosylate = p‐CH3PhSO3–), [Fe(G1‐DPBE)3](triflate)2·xH2O {3; G1‐DPBE = 3,5‐bis(3,5‐didodecaoxybenzyloxy)‐N‐[1,2,4]triazol‐4‐ylbenzamide}, [Fe(G1‐DPBE)3](tosylate)2·xH2O (4) and [Fe(G1‐DPBE)3](BF4)2·xH2O (5) were designed and synthesized. Magnetic and thermal properties of these novel complexes were characterized by magnetic susceptibility measurements, 57Fe Mössbauer spectroscopy and thermogravimetric analysis or differential scanning calorimetry, respectively. All dendritic complexes under study show different spin‐transition behaviour with respect to the nature of different dendritic ligands and counteranions. Complexes 1 and 2 have pronounced effects of a spin‐state change during the first heating process and gradual spin‐transition properties for further temperature treatments, whereas 3 and 4 exhibited a very sharp spin‐state change in the first heating procedures. Complex 5 showed a gradual spin‐transition curve. In this paper, we report how themagnetic properties of these complexes are correlated with noncoordinated water molecules and their effects on spin states.

Crystal structure of [Cs2Na(H2O)2(C23H16O3)(C23H15O3)3

The crystal structure of a double salt of sodium and cesium with 2-diphenylacetyl-1,3-indandione of the composition [Cs2Na(H2O)2(C23H16O3)(C23H15O3)3] (I) was studied by X-ray crystallography. The crystals of I are monoclinic, Z = 2, space group P21/n, a = 10.212(2) A, b = 23.479(5) A, c = 15.638(3) A, β = 98.30(03)°. The compound contains [Cs2NaO10] trimers, in which the central Na atom shares two edges with two Cs atoms through deprotonated bridging ligands. The trimers are connected to adjacent trimers by paired C-H...O contacts to form layers. The layers form an infinite open framework via hydrogen bonds between the oxygen atoms of keto groups of noncoordinated indandione moieties and water molecules that enter the cesium coordination sphere in trimers of the adjacent layers.

The Effect of Distal Heme Pocket Mutations on the Water Accessible Areas in Myoglobin

Internal water molecules are important to protein structure and function. A non-coordinated water molecule in the distal pocket of a myoglobin has been shown to be the dominate factor in controlling the binding of CO to the heme active site. We previously developed a method to experimentally measure the entry of internal water into the distal pockets of Mb mutants after photodissociation of CO. In order to better understand what factors control the occupancy of this disordered water in the protein we compared the occupancy with the size of the mutated residue and hydrophobicity. We see little correlation between residue size and water occupancy and a good correlation between water occupancy and hydrophobicity. In order to better understand what factors contribute to internal water occupancy, we further examined how cavity volume and the dynamic behavior of the distal histidine influence water occupancy. Using a computational approach, we calculated the internal volumes of myoglobin cavities for various mutants. We further characterized these cavities by investigating the dynamic behavior of the H64 residue using molecular dynamics. The data show high flexibility of the H64 in the wild type protein suggesting a mechanism by which water is allowed access to the distal cavity. However, in the distal pocket mutants, the H64 can adopt a more stable conformation thereby reducing water access to the cavity. These findings suggest that the flexibility of the distal histidine plays a key role in influencing water access to the distal cavity and the binding affinity for gaseous ligands. In addition, the long range molecular dynamics was used to assess stability of the cavity bound water for the various mutants. The obtained data showed correlation between hydrophobicity and the water residence time in the cavity.

The Effect of Non-Coordinated Water in the Heme Pocket on the Ligand Binding Dynamics of Heme Proteins

Water molecules in internal protein cavities play fundamental roles in satisfying the H-bonding potentials of main chain atoms in turns, coils, and loops, determining the stability and rigidity of proteins, shifting the pKa values of buried ionizable residues, and modulating dynamical processes such as folding, catalysis, and proton transfers. Detecting these internal water molecules is sometimes obscured in x-ray crystallography due to positional disorder. We have developed a spectrokinetic assay that accurately detects the presence of a non-coordinated water molecule in the distal heme pocket of myoglobin and in a series of distal pocket mutants, including many where this water molecule is positionally disordered. We also have shown that this water plays a major role in determining the observed bimolecular recombination rate constant. We show that 1) this water molecule modulates the ligand binding dynamics of a series of H64, L29 and V68 mutants; 2) it plays the major role in the observed pH dependence of the CO recombination kinetics between pH 4 and 7 with the protonation of the distal histidine acting as a switch to change water occupancy; and 3) it may also modulate ligand binding dynamics in isolated hemoglobin chains, with the occupancy being larger in the alpha chains. Accurately measuring water occupancy in heme proteins answers crucial questions about water in apolar or slightly polar protein cavities and clarifies the role internal water molecules play in modulating protein function.

Synthesis and Crystal Structure of Two Decavanadates Cluster Metal Complexes: [Co(H2O)6]2[H2V10O28]·6H2O and (NH4)2[Ca(H2O)7]2[V10O28

Two new decavanadate metal complexes, [Co(H2O)6]2[H2V10O28]·6H2O (1) and (NH4)2[Ca(H2O)7]2[V10O28] (2), have been synthesized under hydrothermal condition by using chlorhydric acid as the initiator at 120 °C. The aqueous NaVO3 solution with an aqueous solution of CoCl2·6H2O were used for generating 1 and aqueous CaCl2·2H2O and NH4VO3 solution were employed for creating 2. Compound 1 consisted of discrete hexa-aqua-cobalt [Co(H2O)6]2+ cations, [H2V10O28]4− anions and non-coordination water molecules. Compound 2 were composed of hepta-aqua-calcium [Ca(H2O)7]2+ cations, ammonium NH4+ and [V10O28]6− anion. For compound 2, the distorted pentagonal bipyramid [Ca(H2O)7]2+ is uncommon. In the crystal lattice, hydrogen bonds played an important role on connecting cations, anions and non-coordinated water molecules to form the three-dimensional network.

Optical Detection of Disordered Water within a Protein Cavity

Internal water molecules are important to protein structure and function, but positional disorder and low occupancies can obscure their detection by X-ray crystallography. Here, we show that water can be detected within the distal cavities of myoglobin mutants by subtle changes in the absorbance spectrum of pentacoordinate heme, even when the presence of solvent is not readily observed in the corresponding crystal structures. A well-defined, noncoordinated water molecule hydrogen bonded to the distal histidine (His64) is seen within the distal heme pocket in the crystal structure of wild type (wt) deoxymyoglobin. Displacement of this water decreases the rate of ligand entry into wt Mb, and we have shown previously that the entry of this water is readily detected optically after laser photolysis of MbCO complexes. However, for L29F and V68L Mb no discrete positions for solvent molecules are seen in the electron density maps of the crystal structures even though His64 is still present and slow rates of ligand binding indicative of internal water are observed. In contrast, time-resolved perturbations of the visible absorption bands of L29F and V68L deoxyMb generated after laser photolysis detect the entry and significant occupancy of water within the distal pockets of these variants. Thus, the spectral perturbation of pentacoordinate heme offers a potentially robust system for measuring nonspecific hydration of the active sites of heme proteins.

Di-μ-benzoato-κ3O,O′:O;κ3O:O,O′-bis[(acetato-κO)(1,10-phenanthroline-κ2N,N′)lead(II)] dihydrate

The title compound, [Pb2(CH3COO)2(C7H5O2)2(C12H8N2)2]·2H2O, consists of dimeric units built up around a crystallographic centre of symmetry and two non-coordinating water mol­ecules. Each PbII unit is six-coordinated by a bidentate 1,10-phenanthroline (phen) ligand, a monodentate acetate anion and a bidentate benzoate anion, which also acts as a bridge linking the two PbII atoms. The crystal packing is stabilized by O—H⋯O hydrogen bonds and by π–π inter­actions between the phen rings of neighboring mol­ecules, with a centroid–centroid distance of 3.577 (3) Å.

Catena-Poly[[[aqua(ethylenediamine-κ2N,N′)(nitrato-κO)copper(II)]-μ-4,4′-dithiodipyridine-κ2N:N′] nitrate monohydrate

The title compound, {[Cu(NO(3))(C(2)H(4)N(2))(C(10)H(8)N(2)S(2))(H(2)O)]NO(3).H(2)O}(n), is composed of a one-dimensional linear coordination polymer involving cis-protected copper(II) ions and a 4,4'-dithiodipyridine bridging ligand. The polymeric chains run along the c-axis direction. N-H...O and O-H...O hydrogen bonds involving the coordinating amine groups, nitrate ions and water molecules, as well as cocrystallized noncoordinating nitrate ions and water molecules, generate a three-dimensional structure.

Poly[[μ4-tartrato-cadmium(II)] 0.167-hydrate

The title compound, {[Cd(C4H4O6)]·0.167H2O}n, adopts a three-dimensional network structure in which each CdII ion is chelated by two pairs of carboxyl­ate and hydroxyl O atoms from two tartrate anions, and is additionally linked to two O atoms of two carboxyl­ate groups that are not involved in chelation. The asymmetric unit has four independent cadmium atoms, two of which lie on special positions of 2 site symmetry. The tartrate anions all lie on general positions. All hydroxyl groups are engaged in O—H⋯O hydrogen-bonds, one of which is also bifurcated. The non-coordinating water molecule is situated on a site with half-occupation.

The coordination polymers poly[μ-4,4′-bipyridyl-di-μ-formato-copper(II)] andcatena-poly[[[diaqua(1-benzofuran-2,3-dicarboxylato)copper(II)]-μ-1,2-di-4-pyridylethane] dihydrate

The title compounds, [Cu(CHO(2))(2)(C(10)H(8)N(2))](n), (I), and {[Cu(C(10)H(4)O(5))(C(12)H(12)N(2))(H(2)O)(2)].2H(2)O}(n), (II), are composed of one-dimensional linear coordination polymers involving copper(II) ions and bidentate bipyridyl species. In (I), the polymeric chains are located on twofold rotation axes at (x, x, 0) and are arranged in layered zones centered at z = 0, 1/4, 1/2 and 3/4 parallel to the ab plane of the tetragonal crystal. Weak coordination of the formate anions of one layer to the copper centers of neighboring layers imparts a three-dimensional connectivity to this structure. In (II), the polymeric chains propagate parallel to the a axis of the crystal. Noncoordinated water molecules link the chains through O-H...O hydrogen bonding in directions perpendicular to c, imparting to the entire structure three-dimensional connectivity. The metal ions adopt distorted octahedral and square-based pyramidal environments in (I) and (II), respectively. This study indicates that, under the given conditions, extended coordination involves Cu(II) centers associating with the bipyridyl ligands rather than with the competing benzofurandicarboxylate entities.

Two- and three-dimensional hydrated coordination polymers of diaqualanthanum(3+) ions with 2-hydroxypropanedioate, oxalate and acetate anions as bridging ligands

The title compounds, poly[[tetraaquadi-mu-2-hydroxypropanedioato-mu-oxalato-dilanthanum(III)] tetrahydrate], {[La(2)(C(2)O(4))(C(3)H(2)O(5))(2)(H(2)O)(4)].4H(2)O}(n), (I), and poly[[tetra-mu-acetato-tetraaqua-mu-oxalato-dilanthanum(III)] dihydrate], {[La(2)(C(2)O(4))(C(2)H(3)O(2))(4)(H(2)O)(4)].2H(2)O}(n), (II), represent crystalline hydrates of coordination polymers of diaqualanthanum(3+) ions with different combinations of bridging carboxylate ligands, viz. 2-hydroxypropanedioate and oxalate in a 2:2:1 ratio in (I), and acetate and oxalate in a 2:4:1 ratio in (II). While the acetate component was one of the reactants used, the other ligands were obtained in situ by aerial oxidation of the dihydroxyfumaric acid present in the reactions. The crystal structure of (I) consists of two-dimensional polymeric arrays with water molecules intercalated between and hydrogen bonded to the arrays. The oxalate components are located on inversion centres. The crystal structure of (II) reveals an open three-dimensional polymeric connectivity between the interacting components, with the solvent water molecules incorporated within the intralattice voids and hydrogen bonded to the polymeric framework. The La(III) ion and the noncoordinated water molecules are located on axes of twofold symmetry. The oxalate group is centred at the 222 symmetry site, the intersection of the three rotation axes. The coordination number of the La(III) ion in the two structures is 10. The significance of this study lies mainly in the characterization of two new coordination polymers, as well as in the confirmation that dihydroxyfumaric acid tends to rearrange to form smaller components in standard laboratory procedures, and should be considered a poor reagent for formulating hybrid coordination polymers with metal ions.

Systematic investigation on the coordination chemistry of a sulfonated monoazo dye: Ligand-dominated d- and f-block derivatives

Ten coordination compounds based on a sulfonated monoazo dye, formulated as M(H(2)O)(2)(4,4'-abs)(2) (M = Mn , Co , Cu , Zn , Cd and Pb ; 4,4'-abs = 4-aminoazobenzene-4'-sulfonic anion), Ag(4,4'-abs) (), [Ln(H(2)O)(phen)(2)(4,4'-abs)(3)].3H(2)O (Ln = Gd , Tb , and Ho ; phen = 1,10-phenanthroline), as well as the parent ligand L [(4,4'-Habs)(2).4H(2)O] and precursor NaL.HL [Na(4,4'-abs)(4,4'-Habs)] were successfully isolated. Structural analyses revealed that the structures of compounds, and vary according to the coordination geometries of the metal ions, and vary from double-strand chain structures () to a 3-D pillared-layer framework to mononuclear complexes. The double-strand chain structures of are isostructural, and are built on octahedral metal centers and double bridging 4,4'-abs ligands coordinating via terminal N- and O-donors. The silver-containing compound displays a pillared-layer structure constructed from 4.8(2) silver sulfonate nets pillared by the linear backbones of 4,4'-abs ligands. Compounds , which are also isostructural, possess mononuclear structures consisting of a metal cation, three 4,4'-abs anions, two auxiliary phen ligands, one aqua ligand and three non-coordinated water molecules. Evidence on two series of isostructural compounds indicates that structures of d- and f-block metal derivatives are dominated by the coordination mode of the ligands. The surface chemistry of compound has been investigated based on the LBL (layer-by-layer) technique. The as-synthesized multilayer films with different composite components exhibit different surface behaviours.

Poly[[aquatri-μ3-hydroxido-(μ4-2-phosphonatoethanesulfonato)dierbium(III)] monohydrate

The crystal structure of the title compound, {[Er2(C2H4O6PS)(OH)3(H2O)]·H2O}n, consists of two Er3+ ions, one (C2H4O6PS)3− ion, three OH− ions, and two water mol­ecule. The Er3+ ions form ErO8 polyhedra., which are connected by μ- and μ3-O atoms. Thus, inorganic Er–O–Er layers of edge- and face-sharing polyhedra are observed. Whereas most often in metal phosphono­sulfonates the organic linker bridges adjacent layers, in the title compound, the (O3PC2H4SO3)3− anion is only connected to one Er–O–Er layer. Short interatomic O⋯O distances [2.898 (8), 2.997 (14) and 2.768 (10) Å] indicate hydrogen bonding between the layers. The noncoordinated water mol­ecules are located between the layers.

New indium selenite-oxalate and indium oxalate with two- and three-dimensional structures

Two new indium(III) compounds with extended structures, [In 2(SeO 3) 2(C 2O 4)(H 2O) 2]·2H 2O ( I) and [NH 3(CH 2) 2NH 3][In(C 2O 4) 2] 2·5H 2O ( II), have been prepared under mild hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. Compound I crystallizes in the triclinic system, space group P-1, with a=5.2596(11) Å, b=6.8649(14) Å, c=9.3289(19) Å, α=101.78(3)°, β=102.03(3)°, γ=104.52(3)°, while compound II crystallizes in the orthorhombic system, space group Fdd2, with a=15.856(3) Å, b=31.183(6) Å, c=8.6688(17) Å. In compound I, indium-selenite chains are bridged by oxalate units to form two-dimensional (2D) In 2(SeO 3) 2C 2O 4 layers, separated by non-coordinating water molecules. In compound II, the indium atoms are connected through the oxalate units to generate a 3D open framework containing cross-linked 12- and 8-membered channels.

Thermal degradation studies on some lanthanide—edta complexes containing hydrazinium cation

Lighter and heavier lanthanide(III) ions react with dihydrazinium salts of ethylenediaminetetraacetic acid (H4edta) in aqueous solution to yield hydrazinium lanthanide ethylenediaminetetraacetate hydrate, N2H5[Ln(edta)(H2O)3]·(H2O)5 where Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy. The numbers of water molecules present inside the coordination sphere have been confirmed by X-ray single crystal studies. The presence of five water molecules as lattice water is clearly shown by the mass loss from the TG analyses. Dehydration of a known amount (1 g) of each sample were carried out at constant temperature (100–110°C) for about 5 min further confirms the number of non-coordinated water molecules. The complexes after the removal of lattice water undergo multi-step decomposition to give respective metal oxide as the final product. The DTA shows endotherms for dehydration and exotherms for the decomposition of the anhydrous complexes. The formation of the metal oxides was confirmed by X-ray powder diffraction studies.

The pH Dependence of Heme Pocket Hydration and Ligand Rebinding Kinetics in Photodissociated Carbonmonoxymyoglobin

We monitored the occupancy of a functionally important non-coordinated water molecule in the distal heme pocket of sperm whale myoglobin over the pH range 4.3-9.4. Water occupancy was assessed by using time-resolved spectroscopy to detect the perturbation of the heme visible band absorption spectrum caused by water entry after CO photodissociation ( Goldbeck, R. A., Bhaskaran, S., Ortega, C., Mendoza, J. L., Olson, J. S., Soman, J., Kliger, D. S., and Esquerra, R. M. (2006) Proc. Natl. Acad. Sci. U. S. A. 103, 1254-1259 ). We found that the water occupancy observed during the time interval between ligand photolysis and diffusive recombination decreased by nearly 20% as the pH was lowered below 6. This decrease accounted for most of the concomitant increase in the observed CO bimolecular recombination rate constant, as the lower water occupancy presented a smaller kinetic barrier to CO entry into the pocket at lower pH. These results were consistent with a model in which the distal histidine, which stabilizes the water molecule within the distal pocket by accepting a hydrogen bond, tends to swing out of the pocket upon protonation and destabilize the water occupancy at low pH. Extrapolation of this model to lower pH suggests that the additional increase in ligand association rate constant observed previously in stopped-flow studies at pH 3 may also be due in part to reduced distal water occupancy concomitant with further His64 protonation and coupled protein conformational change.

Adaptable coordination of U(IV) in the 2D-(4,4) uranium oxalate network: From 8 to 10 coordinations in the uranium (IV) oxalate hydrates

Crystals of uranium (IV) oxalate hydrates, U(C 2O 4) 2·6H 2O ( 1) and U(C 2O 4) 2·2H 2O ( 2), were obtained by hydrothermal methods using two different U(IV) precursors, U 3O 8 oxide and nitric U(IV) solution in presence of hydrazine to avoid oxidation of U(IV) into uranyl ion. Growth of crystals of solvated monohydrated uranium (IV) oxalate, U(C 2O 4) 2·H 2O·(dma) ( 3), dma=dimethylamine, was achieved by slow diffusion of U(IV) into a gel containing oxalate ions. The three structures are built on a bi-dimensional complex polymer of U(IV) atoms connected through bis-bidentate oxalate ions forming [U(C 2O 4)] 4 pseudo-squares. The flexibility of this supramolecular arrangement allows modifications of the coordination number of the U(IV) atom which, starting from 8 in 1 increases to 9 in 3 and, finally increases, to 10 in 2. The coordination polyhedron changes from a distorted cube, formed by eight oxygen atoms of four oxalate ions, in 1, to a mono-capped square anti-prism in 3 and, finally, to a di-capped square anti-prism in 2, resulting from rotation of the oxalate ions and addition of one and two water oxygen atoms in the coordination of U(IV). In 1, the space between the ∞ 2[U(C 2O 4) 2] planar layers is occupied by non-coordinated water molecules; in 2, the space between the staggered ∞ 2[U(C 2O 4) 2·2H 2O] layers is empty, finally in 3, the solvate molecules occupy the interlayer space between corrugated ∞ 2[U(C 2O 4) 2·H 2O] sheets. The thermal decomposition of U(C 2O 4) 2·6H 2O under air and argon atmospheres gives U 3O 8 and UO 2, respectively.

Hydrothermal synthesis and structural characterization of a family of lanthanide tartrates: [Ln 2(C 4H 4O 6) 3(H 2O) 3]·1.5H 2O (Ln = La, Ce, Pr, Nd, Sm)

Coordination polymers containing lanthanides with tartaric acid [Ln 2(C 4H 4O 6) 3(H 2O) 3]·1.5H 2O (Ln = La, Ce, Pr, Nd, Sm and C 4H 4O 6 = d(−) or l(+) tartrate anion) have been synthesized using hydrothermal techniques and characterized by single crystal X-ray diffraction. The compounds are all isotypic with a monoclinic crystal system in the P2 1/ n space group. The asymmetric units of coordination polymers contain two metal centers having different coordination environments. One metal is bonded to four tartrate groups having three d and one l isomers (or three l and one d isomers), whereas the other metal is bonded to five tartrate groups having two d and three l isomers (or two l and three d isomers). Each trivalent metal center is coordinated to nine oxygen atoms that originate from carboxylate and hydroxyl groups of the tartrate anions and water molecules. These new polymers have three-dimensional structures containing open channels that are occupied by non-coordinating water molecules. Thermogravimetric and differential thermal analyses and adsorption of nitrogen have also been studied for these compounds.

Hexaaquanickel(II) bis[2-carboxylato-2-(isothiouronium-S-ylmethyl)propane-1,3-diyl phosphate] hexahydrate

In the title complex, [Ni(H(2)O)(6)](C(6)H(10)N(2)O(6)PS)(2) x 6 H(2)O, the asymmetric unit consists of one-half of an Ni atom (which lies on an inversion centre) with three coordinated water molecules, one complete 2-carboxylato-2-(isothiouronium-S-ylmethyl)propane-1,3-diyl phosphate anion and three noncoordinated water molecules. The hexaaquanickel(II) cations have distorted octahedral coordination and are connected via water chains to form two-dimensional supramolecular networks parallel to the ab plane. The phosphate ester anion is linked via N-H...O and O-H...O hydrogen bonds, thus creating various ring, dimer and chain hydrogen-bonding patterns, and building up a second two-dimensional supramolecular network parallel to the ab plane. The crystal structure is further stabilized by an intra- and interlayer hydrogen-bond network. This work illustrates that a carboxylate with a caged phosphate ester can open its ring in the presence of dichloridotetrakis(thiourea)nickel, and the resulting polyfunctional anion can be used for constructing a complex hydrogen-bonding scheme.

Two Mononuclear Compounds with bis(Pyrimidin-2-yl)amine as a Ligand and as a Hydrogen-bonded Lattice Molecule. Synthesis, Structure and Spectroscopy of {[M(dipm)(H2O)(A)](dipm)(A)(H2O)} (M = Cd with A = ClO4; and Zn with A = BF4)

Two isostructural mononuclear compounds with formula {[Cd(dipm)(H2O)(ClO4)](dipm)(ClO4)(H2O)} (1) {[Zn(dipm)(H2O)(BF4)](dipm)(BF4)(H2O)} (2) and (in which dipm = bis(pyrimidin-2-yl)amine) have been synthesised and characterised by X-ray crystallography and infrared spectroscopy. The structure of compound 1 has been solved in the space group P21/n with a = 18.860(4), b = 8.579(2), c = 20.917(4) A, β = 101.33(3)°, V = 3318.4(12) A3, Z = 4 with final R = 0.0454. The structure of compound 2 has also been solved in the space group P21/n with a = 19.026(4), b = 8.389(1), c = 20.720(4) A, β = 101.37(3)°, V = 3242.2(10) A3, Z = 4 with final R = 0.0689. The geometry around the metal ions is octahedral, and is constituted by four nitrogen atoms from two dipm molecules, an oxygen atom from a water molecule and a semi-coordinating anion atom ( $$ O_{{\rm ClO}_{4}} $$ for compound 1 and $$ F_{{\rm BF}_{4}} $$ for compound 2). In the lattice are also present: a non-coordinating water molecule, an anion molecule and a dipm molecule. For compound 1, the Cd–N distances are between 2.296 and 2.328 A. The $$ \hbox{Cd}{-}\hbox{O}_{{\rm H}_{2}{\rm O}} $$ distance is 2.310 A and the $$ \hbox{Cd}{-}\hbox{O}_{{\rm ClO}_{4}} $$ is 2.477 A. The Zn–N distances in compound 2 are between 2.121 and 2.164 A. The $$ \hbox{Zn}{-}\hbox{O}_{{\rm H}_{2}{\rm O}} $$ distance is 2.147 A and the $$ \hbox{Zn}{-}\hbox{F}_{{\rm BF}_{4}} $$ distance is 2.373 A. A hydrogen bond interaction of the Watson–Crick type is observed between the amine N atom of a dipm ligand to a pyrimidyl N atom and a non-coordinating dipm ligand with N···N distances, which vary from 3.066(5) to 3.109(5) A. Furthermore medium to strong hydrogen bond interactions are present between oxygen atoms of the water molecules and the anions of the compounds. Two isostructural mononuclear compounds with formula {[Cd(dipm)(H2O)(ClO4)](dipm)(ClO4)(H2O)} (1) {[Zn(dipm)(H2O)(BF4)](dipm)(BF4)(H2O)} (2) and (in which dipm = bis(pyrimidin-2-yl)amine) have been synthesised and characterised by X-ray crystallography and infrared spectroscopy. .