Bioinspired manganese(II) complexes with a clickable ligand for immobilisation on a solid support.

Clickable ligands like N,N'-bis((pyridin-2-yl)methyl)prop-2-yn-1-amine (L(1)) and N-((1-methyl-1H-imidazol-2-yl)methyl)-N-(pyridin-2-ylmethyl)prop-2-yn-1-amine (L(2)) have been used to synthesise a series of manganese(ii) complexes for grafting onto appropriate solid supports. These ligands mimic the 2-His-1-carboxylate facial chelation present in the active site of the manganese-dependent dioxygenase (MndD), while the alkyne side function allows grafting of the ligand onto an azido-functionalised support using "click chemistry" methodologies. Such synthetic analogues of the MndD crystallise in the solid state as double halide or pseudohalide-bridged dinuclear manganese(ii) complexes of the general formula [Mn2(µ-X)2X2L2] [L = L(1) with X = Cl (), Br (), and N3 (); L = L(2) with X = N3 ()]. Complexes are characterised by a weak magnetic exchange interaction between the two high-spin Mn(II) ions through the two X(-) bridges (J in the range of -0.059 to +5.30 cm(-1), H = -J·SMn1·SMn2 with SMn1 = SMn2 = 5/2). A new magneto-structural correlation of superexchange bis(µ1,1-azido)dimanganese(ii) complexes has been proposed using both structural parameters, the Mn-N-Mn bridging angle and the Mn-Nazido distance. In MeOH-EtOH solution the dimeric species are present together with few percents of mononuclear manganese(ii) complexes as evidenced by electron paramagnetic resonance (EPR) spectroscopy. Grafting the complexes onto mesoporous silica of MCM-41 type stabilises both dimers and monomers in the nanopores of the solid.

Synthesis, structural analysis, and magnetic properties of ethylmalonate-manganese(II) complexes.

Five manganese(II) complexes of formulas [Mn(2)(Etmal)(2)(H(2)O)(2)(L)](n) (1-4) and {[Mn(Etmal)(2)(H(2)O)][Mn(H(2)O)(4)]}(n) (5) with H(2)Etmal = ethylmalonic acid (1-5) and L = 1,2-bis(4-pyridyl)ethane (bpa) (1), 4,4'-azobispyridine (azpy) (2), 4,4'-bipyridyl (4,4'-bpy) (3), and 1,2-bis(4-pyridyl)ethylene (bpe) (4) were synthesized and structurally characterized by single crystal X-ray diffraction. Their thermal behavior and variable-temperature magnetic properties were also investigated. The structure of the compounds 1-4 consists of corrugated layers of aquamanganese(II) units with intralayer carboxylate-ethylmalonate bridges in the anti-syn (equatorial-equatorial) coordination mode which are linked through bis-monodentate bpa (1), azpy (2), 4,4'-bpy (3), and bpe (4) ligands to build up a three-dimensional (3D) framework. The structure of compound 5 is made up by zigzag chains of manganese(II) ions with a regular alternation of [Mn(H(2)O)(4)](2+) and chiral (either Δ or λ enantiomeric forms) [Mn(Etmal)(2)(H(2)O)](2-) units within each chain. In contrast to the bidentate/bis-monodentate coordination mode of the Etmal ligand in 1-4, it adopts the bidentate/monodentate coordination mode in 5 with the bridging carboxylate-ethylmalonate also exhibiting the anti-syn conformation but connecting one equatorial and an axial position from adjacent metal centers. The manganese-manganese separation through the carboxylate-ethylmalonate bridge in 1-5 vary in the range 5.3167(4)-5.5336(7) Å. These values are much shorter than those across the extended bis-monodentate N-donors in 1-4 with longest/shortest values of 11.682(3) (3)/13.9745(9) Å (4). Compounds 1-5 exhibit an overall antiferromagnetic behavior, where the exchange pathway is provided by the carboxylate-ethylmalonate bridge. Monte Carlo simulations based on the classical spin approach (1-5) were used to successfully reproduce the magnetic data of 1-5.

Monoclinic polymorph of 2-(pyrimidin-2-ylsulfan-yl)acetic acid.

The title compound, C(6)H(6)N(2)O(2)S, is a new polymorphic form of 2-(pyrimidin-2-ylsulfan-yl)acetic acid. Unlike the previous orthorhombic polymorph [Pan & Chen (2009 ▶) Acta Cryst. E65, o652], the mol-ecules are not planar: the aromatic ring makes an angle of 80.67 (17)° with the carboxyl plane. In the crystal, mol-ecules are linked by O-H⋯N hydrogen bonds into chains along [02].

Phenyl-hydrazinium (6-carb-oxy-pyridine-2-carboxyl-ato)(pyridine-2,6-dicarboxyl-ato)cobaltate(II)-pyridine-2,6-dicarb-oxy-lic acid-water (1/1/3).

The asymmetric unit of the title compound, (C(6)H(9)N(2))[Co(C(7)H(3)NO(4))(C(7)H(4)NO(4))]·C(7)H(5)NO(4)·3H(2)O, contains one (6-carb-oxy-pyridine-2-carboxyl-ato)(pyridine-2,6-dicarboxyl-ato)cobaltate(II) anion, one phenyl-hydrazinium cation, one pyridine-2,6-dicarb-oxy-lic acid mol-ecule and three uncoordin-ated water mol-ecules, part of which are disordered. The Co(II) ion is coordinated by a pyridine-2,6-dicarboxyl-ate ion and a 6-carb-oxy-pyridine-2-carboxyl-ate ligand almost perpendicular to each other [the angle between the least-squares planes is 87.38 (4)°] and is surrounded by two O atoms and two N atoms in the equatorial plane and two O atoms in axial positions, resulting in a distorted octa-hedral coordination geometry. There is an extensive three-dimensional network of O-H⋯O and N-H⋯O hydrogen bonds, which link the components.

Dinuclear, tetranuclear and one-dimensional pyrazine-based copper(II) complexes: preparation, X-ray structure and magnetic properties.

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(2)(tppz)(H(2)O)(2)(CF(3)SO(3))(4)] (1), [Cu(tppz)(CrO(4))](n) x 3nH(2)O (2) and [Cu(4)(tppz)(4)(H(2)O)(4)(MoO(4))(2)](CF(3)SO(3))(4) x 7 H(2)O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complex 1 is a dinuclear species where tppz adopts a bis-tridentate bridging mode with an intramolecular copper-copper separation of 6.5221(6) A. Each copper(II) ion in 1 has an elongated octahedral geometry with three tppz nitrogen atoms and a water molecule in the equatorial positions and two triflate oxygen atoms occupying the axial sites. Complex 2 is a uniform copper(II) chain where the copper atoms are bridged by two oxygen atoms of the chromate group (mu(1,2)-CrO(4)), the value of the intrachain metal-metal separation being 4.2614(5) A. Each copper(II) ion in 2 exhibits a somewhat distorted square pyramidal geometry with three nitrogen atoms from a tridentate tppz ligand and a chromate oxygen atom in the basal plane and an oxygen atom of a symmetry-related chromate group in the apical position. Complex 3 is a cyclic tetranuclear compound where peripheral [Cu(tppz)(H(2)O)](2+) units are connected through two molybdate groups, each one adopting the mu(1,1,2)-MoO(4) bridging mode. Regular alternating five [Cu(1) and Cu(4)] and six [Cu(2) and Cu(3)] coordinated copper(II) ions occur in 3 with distorted square pyramidal CuN(3)O(2) and elongated octahedral CuN(3)O(3) surroundings, respectively. The four copper atoms in 3 have in common the presence of a molybdate-oxygen and three tppz-nitrogen atoms in the basal [Cu(1) and Cu(4)]/equatorial [Cu(2) and Cu(3)] planes and a water molecule in the apical [Cu(1) and Cu(4)]/one axial [Cu(2) and Cu(3)] positions whereas the remaining axial position is occupied by a molybdate-oxygen [Cu(2) and Cu(3)]. The shorter intramolecular copper-copper separation is 3.371(1) A [Cu(2)...Cu(3)], the other ones varying in the range 5.537(1)-6.301(1) A. The investigation of the magnetic properties of 1-3 in the temperature range 1.9-295 K has shown the occurrence of intermediate antiferro- [J = -48.0(1) cm(-1) with H = -JS(1) x S(2) (1)], weak ferro- [J = +0.28(1) cm(-1) with H = -JSigma(i)S(i) x S(i+I) (2)] and coexistence of weak ferro- and antiferromagnetic interactions [J(1) = +2.38(2) cm(-1), J(2) = +0.56(2) cm(-1) and J(3) = -1.53(2) cm(-1) with H = -J(1) (S(2) x S(3)) + J(2) (S(1) x S(3) + S(2) x S(4)) + J(3) (S(1) x S(2) + S(3) x S(4)) (3)] between the copper(II) ions across bis-tridentate tppz (1), mu(1,2)-CrO(4) (2), di-mu(1,1)-MoO(4) and mu(1,2)-MoO(4) (3) bridges. The values of the magnetic interactions are analyzed in terms of simple orbital symmetry considerations and compared with those reported for parent systems.

Low-dimensional copper(II) complexes with the trinucleating ligand 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine: synthesis, crystal structures, and magnetic properties.

The preparation and structural characterization of three new copper(II) complexes of formula [Cu(3)(dipyatriz)(2)(H(2)O)(3)](ClO(4))(6) x 2 H(2)O (1), {[Cu(4)(dipyatriz)(2)(H(2)O)(2)(NO(3))(2)(ox)(2)](NO(3))(2) x 2 H(2)O}(n) (2), and [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](NO(3))(3) x 4 H(2)O (3) [dipyatriz = 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine and ox = oxalate] are reported. The structure of 1 consists of trinuclear units [Cu(3)(dipyatriz)(2)(H(2)O)(3)](6+) and uncoordinated perchlorate anions. The two dipyatriz molecules in 1 act as tris-bidentate ligands with the triazine cores being in a quasi eclipsed conformation. Each copper atom in 1 exhibits a distorted square pyramidal geometry CuN(4)O with four pyridyl-nitrogen atoms from two dipyatriz ligands building the basal plane and a water molecule occupying the axial position. The values of the intratrimer copper-copper separation are 8.0755(6) and 8.3598(8) A. Compound 2 exhibits a layered structure of copper(II) ions which are connected through bis-bidentate dipyatriz ligands and bidentate/outer monodentate oxalato groups. The copper atoms in 2 exhibit six- [Cu(1)N(4)O(2)] and five-coordination [Cu(2)N(2)O(3)]. A water molecule and three pyridyl-nitrogen atoms [Cu(1)] and two pyridyl-nitrogen plus two oxalate-oxygen atoms [Cu(2)] define the equatorial plane whereas either an oxalate-oxygen and a pyridyl-nitrogen [Cu(1)] or a nitrate-oxygen [Cu(2)] fill the axial positions. The copper-copper separation through the bridging oxalato is 5.6091(6) A whereas those across dipyatriz vary in the range 7.801(1)-9.079(1) A. The structure of compound 3 contains discrete cage-like hexacopper(II) units [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](3+) where two trinuclear [Cu(3)(dipyatriz)](6+) fragments are connected by three bis-bidentate oxalate ligands, the charge being balanced by three non-coordinated nitrate anions. The values of the intracage copper-copper distance are 5.112(3)-5.149(2) A (across oxalato) and 7.476(2)-8.098(2) A (through dipyatriz). Magnetic susceptibility measurements of polycrystalline samples of 1-3 in the temperature range 1.9-295 K show the occurrence of a weak antiferromagnetic interaction across dipyatriz in 1 [J = -0.08(1) cm(-1), the Hamiltonian being defined as (wedge)H = -J ((wedge)S(1).(wedge)S(2) + (wedge)S(1) x (wedge)S(3) + (wedge)S(2) x (wedge)S(3))] and weak ferro- (2) and strong antiferromagnetic (3) interactions through the oxalato bridge in 2 [J = +0.45(2) cm(-1)] and 3 [J = -390(1) cm(-1)]. The use of the dipyatriz-containing copper(II) species as a building block to design homo- and heterometallic magnetic compounds is analyzed and discussed.

Ligand effects on the structures and magnetic properties of tricyanomethanide-containing copper(II) complexes.

The preparation, crystal structure and magnetic properties of four heteroleptic copper(II) complexes with the tricyanomethanide (tcm(-)) and the heterocyclic nitrogen donors 3,6-bis(2-pyridyl)pyridazine (dppn), 2,5-bis(2-pyridyl)pyrazine (2,5-dpp), 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) and 2,3-bis(2-pyridyl)quinoxaline (2,3-dpq) are reported, {[Cu(2)(dppn)(OH)(tcm)(2)] x tcm}(n) (1), {[Cu(2,5-dpp)(tcm)] x tcm}(n) (2), {[Cu(2)(2,3-dpp)(2)(tcm)(3)(H(2)O)(0.5)] x tcm x 0.5H(2)O}(n) (3) and [Cu(2,3-dpq)(tcm)(2)](n) (4). 1 has a ladder-like structure with single mu-1,5-tcm ligands forming the sides and a bis-bidentate dppn and a single mu-hydroxo providing the rung. Each copper atom in 1 exhibits a distorted square pyramidal CuN(4)O surrounding: the basal plane is built by the hydroxo-oxygen, a nitrile-nitrogen atom from a tcm group and one pyrazine and a pyridyl nitrogen atoms from the dppn whereas the apical position is filled by a nitrile-nitrogen atom from a symmetry-related tcm ligand. The structures of 2-4 consists of zig-zag (2 and 3)/linear (4) chains of copper(II) ions which are bridged by either bis-bidentate 2,5-dpp (2) and 2,3-dpp (3) molecules or single mu-1,5-tcm (4) groups. The copper atoms in 2 and 4 are five coordinated with distorted trigonal bipyramidal (2) and square pyramidal (4) CuN(5) surroundings. The axial positions in 2 are occupied by two pyridyl-nitrogen atoms from two 2,5-dpp ligands whereas the trigonal plane is built by a nitrile-nitrogen from a terminally bound tcm group and two pyrazine nitrogen atoms from two 2,5-dpp molecules. The basal plane in 4 is defined by a pyridyl and a pyrazine nitrogen atoms from the bidentate 2,3-dpq ligand and two nitrile nitrogen atoms from two tcm groups (one terminal and the other bridging) whereas the apical position is filled by a nitrile nitrogen from another tcm ligand. The crystallographically independent copper atoms in 3 [Cu(1) and Cu(2)] exhibit elongated octahedral geometries being defined by four nitrogen atoms from two 2,3-dpp groups [Cu(1) and Cu(2)] either two terminally bound tcm ligands [Cu(1)] or a water molecule and a monodentate tcm ligand [Cu(2)] in cis positions. Magnetic susceptibility measurements for 1-4 in the temperature range 1.9-295 K reveal the occurrence of strong [J ca.-1000 cm(-1) (1); H = -JS(A) x S(B)] and weak [J = -0.13 (2), -0.67 (3) and -0.18 cm(-1) (4); H = -J Sigma(I)S(i) x S(i+1)] antiferromagnetic interactions in agreement with the different nature of the exchange pathways involved, diazine and single mu-hydroxo (1) and the extended 2,5-dpp (2), 2,3-dpp (3) and single mu-1,5-tcm (4) bridges with copper-copper separations of 3.363(8) (1), 7.111(1) (2), 6.823(1) and 7.056(1) (3) and 7.446(1) A (4).