Crystal Structures of [Mn2(H2O)4(phen)2(C4H4O4)2] · 2 H2O and [Mn(phen)2(H2O)2][Mn(phen)2(C4H4O4)](C4H4O4) · 7 H2O

Reactions of 1,10‐phenanthroline monohydrate, Na₂C₄H₄O₄ · 6 H₂O and MnSO₄ · H₂O in CH₃OH/H₂O yielded a mixture of [Mn₂(H₂O)₄(phen)₂(C₄H₄O₄)₂] · 2 H₂O ( 1 ) and [Mn(phen)₂(H₂O)₂][Mn(phen)₂(C₄H₄O₄)](C₄H₄O₄) · 7 H₂O ( 2 ). The crystal structure of 1 (P1 (no. 2), a = 8.257(1) Å, b = 8.395(1) Å, c = 12.879(2) Å, α = 95.33(1)°, β = 104.56(1)°, γ = 106.76(1)°, V = 814.1(2) ų, Z = 1) consists of the dinuclear [Mn₂(H₂O)₄(phen)₂(C₄H₄O₄)₂] molecules and hydrogen bonded H₂O molecules. The centrosymmetric dinuclear molecules, in which the Mn atoms are octahedrally coordinated by two N atoms of one phen ligand and four O atoms from two H₂O molecules and two bis‐monodentate succinato ligands, are assembled via π‐π stacking interactions into 2 D supramolecular layers parallel to (101) (d(Mn–O) = 2.123–2.265 Å, d(Mn–N) = 2.307 Å). The crystal structure of 2 (P1 (no. 2), a = 14.289(2) Å, b = 15.182(2) Å, c = 15.913(2) Å, α = 67.108(7)°, β = 87.27(1)°, γ = 68.216(8)°, V = 2934.2(7) ų, Z = 2) is composed of the [Mn(phen)₂(H₂O)₂]²⁺ cations, [Mn(phen)₂(C₄H₄O₄)] complex molecules, (C₄H₄O₄)^2– anions, and H₂O molecules. The (C₄H₄O₄)^2– anions and H₂O molecules form 3 D hydrogen bonded network and the cations and complex molecules in the tunnels along [001] and [011], respectively, are assembled via the π‐π stacking interactions into 1 D supramolecular chains. The Mn atoms are octahedrally coordinated by four N atoms of two bidentate chelating phen ligands and two water O atoms or two carboxyl O atoms (d(Mn–O) = 2.088–2.129 Å, d(Mn–N) = 2.277–2.355 Å). Interestingly, the succinato ligands in the complex molecules assume gauche conformation bidentately to chelate the Mn atoms into seven‐membered rings.     

{[Mn2(μ3‐Tda)2(μ‐H2O)(H2O)2(bipy)]·DMF}n – a 2D Manganese(II) Coordination Polymer involving Six‐membered Binuclear Metallacycle Nodes

The single crystal X‐ray analysis of a novel thiophene‐2,5‐dicarboxylic acid (H₂Tda) Manganese(II) coordination polymer, {Mn₂(μ₃‐Tda)₂(μ‐H₂O)(H₂O)₂(bipy)]·DMF}_n, shows two different types of Mn²⁺‐ions with environment of Mn1O₆ and Mn2O₄N₂, and the complex is a two‐dimensional polymer as a result of bridging (Tda)^2? ligands and by connecting the carboxylate‐ and water‐bridged {Mn₂(μ‐Tda)₂(μ‐H₂O)} nodes.     

Synthesis,Structural Characterization and Thermal Stability of [Mn(3‐bpd)2(NCS)2(H2O)2]·2H2O (1) and {[Mn(bpe)(NCS)2(H2O)2]·(3‐bpd)·(bpe)·H2O}n (2) from One‐Pot Crystallization

Two supramolecular architectures, [Mn(3‐bpd)₂(NCS)₂(H₂O)₂]·2H₂O ( 1 ) and {[Mn(bpe)(NCS)₂(H₂O)₂]·(3‐bpd)·(bpe)·H₂O}_n ( 2 ) [bpe = 1,2‐bis(4‐pyridyl)ethylene and 3‐bpd = 1,4‐bis(3‐pyridyl)‐2,3‐diaza‐1,3‐butadiene] have been synthesized and characterized by spectroscopic, elemental and single crystal X‐ray diffraction analyses. Compound 1 crystallizes in the monoclinic system, space group P2₁/c, with chemical formula C₂₆H₂₈Mn N₁₀O₄S₂, a = 9.1360(6), b = 9.7490(6), c = 17.776(1) Å, β = 93.212(1)°, and Z = 2 while compound 2 crystallizes in the orthorhombic system, space group P2₁2₁2₁, with chemical formula C₃₈H₃₆Mn₁N₁₀O₃S₂, a = 14.1902(6), b = 15.4569(7), c = 18.2838(8) Å, α = β = γ = 90°, and Z = 4. Structural determination reveals that the coordination geometry at Mn(II) in compound 1 or 2 is a distorted octahedral which consists of two nitrogen donors of two NCS^?ligands, two oxygen donors of two water molecules, and two nitrogen donors of two 3‐bpd ligands for 1 and two dpe ligands for 2 , respectively. The two 3‐bpd ligands in 1 adopt a monodentate binding mode and the dpe in 2 adopts a bismonodentate bridging mode to connect the Mn(II) ions forming a 1D chain‐like coordination polymer. Both the π‐π stacking interactions between the coordinated and the free pyridyl‐based ligands and intermolecular hydrogen bonds among the coordinated and the crystallized water molecules and the free pyridyl‐based ligands play an important role in construction of these 3D supramolecular architectures.     

Synthesis,Structure, Magnetic Properties,and Catalase‐like Activity of Methoxy‐bridged Manganese(III) Coordination Polymer containing Hydrazone based (O,N,O)2‐Donor Ligand

A 1D coordination polymer of manganese(III) with a hydrazone‐based ligand, [Mn₂(L)(μ‐OCH₃)₂(OHCH₃)₂]_n ( 1 ), was synthesized and characterized by elemental analyses and spectroscopic methods {H₄L = bis[(2‐hydroxynaphthalen‐1‐yl)methylene]adipohydrazide}. The crystal structure of 1 was determined by X‐ray crystallography. The two dianionic domains of the ligand adopt trans configuration, and each coordinates in a tridentate mode via the O, N, O′‐donor atoms to a Mn^III ion forming a dinuclear compound. The methoxy ligands provide an asymmetric bridge between two central manganese atoms, which lead to the formation of a 1D coordination polymer. A 2D supramolecular structure is formed by hydrogen bonding interactions between the 1D chains. Although the methoxy ligands are labile, the polymer preserves its oligonuclearity in the solution. Temperature‐dependent magnetic susceptibility studies proved the presence of a weak antiferromagnetic interaction between manganese(III) ions with J = –3.2 cm^–1, which results from axial distortion of the manganese coordination environment. Compound 1 showed catalase‐like activity in disproportionation of H₂O₂.     

A New Maleato-Bridged Mn(II) Phen Complex: Structure and Magnetic Properties of Mn(phen)(C4H2O4)

Reaction of freshly-precipitated MnCO₃, phenanthroline monohydrate and maleic acid in CH₃OH/H₂O (pH = 6.23) at 50°C afforded a new maleato bridged, catenated coordination polymer Mn(phen)(C₄H₂O₄), where the Mn atoms are each octahedrally coordinated by two N atoms of one phen ligand and four O atoms of three maleato ligands (d(Mn-N) = 2.300, 2.331 Å; d(Mn-O) = 2.112-2.207 Å). The maleato ligand chelates one Mn atom to form a seven membered ring while two carboxylate groups of different maleato ligands bridge two Mn atoms to form an eight-membered ring, 1D ¹ _∞[Mn(phen)(C₄H₂O₄)_3/3] chains being generated in a sequence of seven- and eight-membered rings. Significant interchain π-π stacking interactions are responsible for the supramolecular assembly of the polymeric ¹ _∞[Mn(phen)(C₄H₂O₄)_3/3] chains into 2D layers. At low temperatures, the title complex becomes antiferromagnetic with T _Née1 = 7 K and follows the Curie-Weiss law _χm (T + 9.82) = 4.140 cm³ mol^-1 K between 30-300 K.     

A candidate for a single‐chain magnet: [Mn3(OAc)6(py)2(H2O)2]n (OAc is acetate and py is pyridine)

The title complex, catena‐poly[di‐μ₃‐acetato‐κ⁶O:O:O′‐tetra‐μ₂‐acetato‐κ⁴O:O;κ⁴O:O′‐diaquabis(pyridine‐κN)trimanganese(II)], [Mn₃(CH₃COO)₆(C₆H₅N)₂(H₂O)₂]_n, is a true one‐dimensional coordination polymer, in which the Mn^II centres form a zigzag chain along [010]. The asymmetric unit contains two metal centres, one of which (Mn1) lies on an inversion centre, while the other (Mn2) is placed close to an inversion centre on a general position. Since all the acetates behave as bridging ligands, although with different μ₂‐ and μ₃‐coordination modes, a one‐dimensional polymeric structure is formed, based on trinuclear repeat units (Mn1...Mn2...Mn2′), in which the Mn2 and Mn2′ sites are related by an inversion centre. Within this monomeric block, the metal–metal separations are Mn1...Mn2 = 3.36180 (18) Å and Mn2...Mn2′ = 4.4804 (3) Å. Cation Mn1, located on an inversion centre, displays an [MnO₆] coordination sphere, while Mn2, on a general position, has a slightly stronger [MnO₅N] ligand field, as the sixth coordination site is occupied by a pyridine molecule. Both centres approximate an octahedral ligand field. The chains are parallel in the crystal structure and interact via hydrogen bonds involving coordinated water molecules. However, the shortest metal–metal separation between two chains [5.3752 (3) Å] is large compared with the intrachain interactions. These structural features are compatible with a single‐chain magnet behaviour, as confirmed by preliminary magnetic studies.     

A neodymium(III)–ammonium complex involving oxalate and carbonate ligands: (NH4)2[Nd2(C2O4)3(CO3)(H2O)]·H2O

The title compound, di­ammonium aqua‐μ‐carbonato‐tri‐μ‐­oxalato‐dineodymium(III) hydrate, (NH₄)₂[Nd₂(CO₃)(C₂O₄)₃(H₂O)]·H₂O, involving the two ligands oxalate and carbonate, has been prepared hydro­thermally as single crystals. The Nd atoms form a tetranuclear unit across the inversion centre at (,,). Starting from this tetranuclear unit, the oxalate ligands serve to develop a three‐dimensional network. The carbonate group acts as a bis‐chelating ligand to two Nd atoms, and is monodentate to a third Nd atom. The oxalate groups are all bis‐chelating. The two independent Nd atoms are ninefold coordinated and the coordination polyhedron of these atoms is a distorted monocapped antiprism.     

First‐row transition metal–pyridine (py)–sulfate [(py)xM](SO4) complexes (M = Ni,Cu and Zn): crystal field theory in action

The crystal structures of three first‐row transition metal–pyridine–sulfate complexes, namely catena‐poly[[tetrakis(pyridine‐κN)nickel(II)]‐μ‐sulfato‐κ²O:O′], [Ni(SO₄)(C₅H₅N)₄]_n, (1), di‐μ‐sulfato‐κ⁴O:O‐bis[tris(pyridine‐κN)copper(II)], [Cu₂(SO₄)₂(C₅H₅N)₆], (2), and catena‐poly[[tetrakis(pyridine‐κN)zinc(II)]‐μ‐sulfato‐κ²O:O′‐[bis(pyridine‐κN)zinc(II)]‐μ‐sulfato‐κ²O:O′], [Zn₂(SO₄)₂(C₅H₅N)₆]_n, (3), are reported. Ni compound (1) displays a polymeric crystal structure, with infinite chains of Ni^II atoms adopting an octahedral N₄O₂ coordination environment that involves four pyridine ligands and two bridging sulfate ligands. Cu compound (2) features a dimeric molecular structure, with the Cu^II atoms possessing square‐pyramidal N₃O₂ coordination environments that contain three pyridine ligands and two bridging sulfate ligands. Zn compound (3) exhibits a polymeric crystal structure of infinite chains, with two alternating zinc coordination environments, i.e. octahedral N₄O₂ coordination involving four pyridine ligands and two bridging sulfate ligands, and tetrahedral N₂O₂ coordination containing two pyridine ligands and two bridging sulfate ligands. The observed coordination environments are consistent with those predicted by crystal field theory.     

The trigonal–bipyramidal triiodo­thallium(III) complex [TlI3{(CH3)2SO}2]

The title compound, bis(dimethyl sulfoxide)triiodo­thallium(III), [TlI₃(C₂H₆OS)₂], was crystallized from equimolar amounts of Tl^II and I₂ in a dimethyl sulfoxide (DMSO) solution. After the initial redox reaction, the thallium(III)–iodo complex forms and precipitates as a DMSO solvate. In the crystal structure, Tl is surrounded by three iodide ligands in the equatorial plane and two O‐coordinated DMSO mol­ecules in the axial positions, forming a slightly distorted trigonal bipyramid. The complex lies on a twofold rotation axis, making the DMSO mol­ecules and two of the I atoms crystallographically equivalent.     

K2[Mo2O4(C2O4)2(H2O)2]·3H2O

The crystal and molecular structure of dipotassium di‐μ‐oxo‐bis[aqua(oxalato‐O¹,O²)oxomolybdenum(III)] trihydrate, K₂­[Mo₂O₄(C₂O₄)₂(H₂O)₂]·3H₂O, has been determined from X‐ray diffraction data. In the dimeric anion, which has approximate twofold symmetry, each Mo atom is in a distorted octahedral coordination, being bonded to one terminal oxo‐O atom, two bridging O atoms, two O atoms from the oxalato ligand and one from the water mol­ecule. Bond lengths trans to the multiple‐bonded terminal oxo ligand are larger than those in the cis position, confirming the trans influence as a generally valid rule.     

A photochromic dinuclear compound: aquatetrakis(μ‐2,3‐diphenylprop‐2‐enoato)bis(2,3‐diphenylprop‐2‐enoato)ethanolbis(1,10‐phenanthroline)dilanthanum(III)

The title dinuclear complex, (aqua‐1κO)tetrakis(μ‐2,3‐diphenylprop‐2‐enoato‐1:2κ²O:O′)bis(2,3‐diphenylprop‐2‐enoato)‐1κO;2κO‐(ethanol‐2κO)bis(1,10‐phenanthroline)‐1κ²N,N′;2κ²N,N′‐dilanthanum(III), [La₂(C₁₅H₁₁O₂)₆(C₁₂H₈N₂)₂(C₂H₅OH)(H₂O)], contains two similar La^III centres with distorted [LaO₆N₂] bicapped triganol–prismatic coordination polyhedra formed by six phenylcinnamate (PCA⁻ or 2,3‐diphenylprop‐2‐enoate) ligands, two 1,10‐phenanthroline (phen) ligands, a coordinating ethanol molecule and a coordinating water molecule. The two metal centres are bridged by four μ‐PCA⁻ ligands, with the remaining two PCA⁻ ligands coordinated in a monodentate fashion. The noncoordinated carboxylate O atoms on the terminal PCA⁻ ligands form O—H...O hydrogen bonds with the coordinated solvent molecules. Each La centre is also coordinated by a bidentate phen ligand. The PCA⁻ ligands all adopt syn–syn orientations, with the two phenyl rings presenting dihedral angles of about 70°. The compound displays photochromic behaviour both in solution and in the solid state.     

Solvothermal synthesis,crystal structure and properties of Mn2(tren)3[Mo2O2S6]2·1.3H2O exhibiting the new polymeric [Mn2(tren)3] n 4+ chain

The novel oxothiomolybdate Mn₂(tren)₃[Mo₂O₂S₆]₂·1.3H₂O [tren = tris(2-aminoethyl)amine], synthesized under solvothermal conditions, consists of one-dimensional novel [Mn₂(tren)₃] _n ⁴⁺ chains and discrete [Mo₂O₂S₆]^2– anions. There are two crystallographically independent chains and four [Mo₂O₂S₆]^2– anions in the asymmetric unit. Each Mn atom in the cationic chains is sixfold coordinated by N atoms of the chelating tren molecules. Two of the four crystallographically independent Mn atoms are tridentately coordinated by two tren molecules, whereas the other two are coordinated tetradentately by one tren molecule and monodentately by the remaining primary amino groups from the tren molecules that act as tridentate ligands. The tren ligand bonding modes lead to the formation of the polymeric [Mn₂(tren)₃] _n ⁴⁺ chain. One of the four Mn atoms is in the unusual trigonal prismatic coordination state with six surrounding N atoms.     

A one‐dimensional chain structure based on unusual tetranuclear manganese(II) clusters

The title coordination polymer, poly[bis(μ₄‐biphenyl‐2,2′‐dicarboxylato)(dipyrido[3,2‐a:2′,3′‐c]phenazine)manganese(II)], [Mn₂(C₁₄H₈O₄)₂(C₁₈H₁₀N₄)]_n, was obtained through the reaction of MnCl₂·4H₂O, biphenyl‐2,2′‐dicarboxylic acid (H₂dpdc) and dipyrido[3,2‐a:2′,3′‐c]phenazine (L) under hydrothermal conditions. The asymmetric unit contains two crystallographically unique Mn^II ions, one unique L ligand and two unique dpdc ligands. One Mn ion is six‐coordinated by four O atoms from three different dpdc ligands and two N atoms from one L ligand, adopting a distorted octahedral coordination geometry. The distortions from ideal octahedral geometry are largely due to the presence of chelating ligands and the resulting acute N—Mn—N and O—Mn—O angles. The second Mn ion is coordinated in a distorted trigonal bipyramidal fashion by five O atoms from four distinct dpdc ligands. Four Mn^II ions are bridged by the carboxylate groups of the dpdc ligands to form an unusual tetranuclear Mn^II cluster. Clusters are further connected by the aromatic backbone of the dicarboxylate ligands, forming a one‐dimensional chain structure along the b axis. The title compound is the first example of a chain structure based on a tetranuclear Mn^II cluster.     

Triazine based Mn (II) and Mn (II)/Ln (III) complexes: Synthesis,characterization and catecholase activities

In the current work, two triazine‐based multidentate ligands (H₂L¹ and H₂L²) and their homo‐dinuclear Mn (II), mononuclear Ln (III) and hetero‐dinuclear Mn (II)/Ln (III) (Where Ln: Eu or La) complexes were synthesized and characterized by spectroscopic and analytical methods. Single crystals of a homo‐dinuclear Mn (II) complex {[Mn (HL¹)(CH₃OH)](ClO₄·CH₃OH}₂ ( 1 ) were obtained and the molecular structure was determined by X‐ray diffraction method. In the structure of the complex, each Mn (II) ion is seven‐coordinate and one of the phenolic oxygen bridges two Mn (II) centre forming a dimeric structure. The UV–Vis. and photoluminescence properties of synthesized ligands and their metal complexes were investigated in DMF solution and the compounds showed emission bands in the UV–Vis. region. The catecholase enzyme‐like activity of the complexes were studied for 3,5‐DTBC → 3,5‐DTBQ conversion in the presence of air oxygen. Homo‐dinuclear Mn (II) complexes ( 1 and 4 ) were found to efficiently catalyse 3,5‐DTBC → 3,5‐DTBQ conversion with the turnover numbers of 37.25 and 35.78 h^?1 (k_cat), respectively. Mononuclear Eu (III) and La (III) complexes did not show catecholase activity.     

Synthesis,crystal structure,and catalytic properties of a one-dimensional nickel(II) polymer

The title complex [Ni₂(C₁₀H₉N₃)₂(C₁₄H₈O₅)₂] _n , which has an inversion center, midway between two Ni(II) atoms forms a one-dimensional polymer bridged by 4,4′-oxydibenzoate ligands with a Ni…Ni separation of 14.4705(11) Å. The Ni(II) atom is six-coordinated by two N atoms of a bis(2-pyridyl)amine ligand and four O atoms from two 4,4′-oxydibenzoate ligands, to form a distorted octahedron coordination geometry and then are linked via N-H…O and C-H…O hydrogen bonding into a polymeric ribbon structure. The activity and selectivity profiles of the polymer indicate that the optimization temperature and time span are 175°C and 30–40 min for the dehydration of cyclohexanol, respectively.     

A new two‐dimensional managnese(II) coordination polymer constructed by 2,2′‐(1,2‐phenylene)bis(1H‐imidazole‐4,5‐dicarboxylate)

In recent years, N‐heterocyclic carboxylate ligands have attracted much interest in the preparation of new coordination polymers since they contain N‐atom donors, as well as O‐atom donors, and have a rich variety of coordination modes which can lead to polymers with intriguing structures and interesting properties. A new two‐dimensional coordination polymer, namely poly[[μ₃‐2,2′‐(1,2‐phenylene)bis(4‐carboxy‐1H‐imidazole‐5‐carboxylato)‐κ⁶O⁴,N³,N^3′,O^4′:O⁵:O^5′]manganese(II)], [Mn(C₁₆H₈N₄O₈)]_n or [Mn(H₄Phbidc)]_n, has been synthesized by the reaction of Mn(OAc)₂·4H₂O (OAc is acetate) with 2,2′‐(1,2‐phenylene)bis(1H‐imidazole‐4,5‐dicarboxylic acid) (H₆Phbidc) under solvothermal conditions. In the polymer, each Mn^II ion is six‐coordinated by two N atoms from one H₄Phbidc²⁻ ligand and by four O atoms from three H₄Phbidc²⁻ ligands, forming a significantly distorted octahedral MnN₂O₄ coordination geometry. The Mn^II ions are linked by hexadentate H₄Phbidc²⁻ ligands, leading to a two‐dimensional structure parallel to the ac plane. In the crystal, adjacent layers are further connected by N—H…O hydrogen bonds, forming a three‐dimensional structure in the solid state.     

O2 Activation and Double CH Oxidation by a Mononuclear Manganese(II) Complex

A Mn^II complex, [Mn(dpeo)₂]²⁺ (dpeo=1,2‐di(pyridin‐2‐yl)ethanone oxime), activates O₂, with ensuing stepwise oxidation of the methylene group in the ligands providing an alkoxide and ultimately a ketone group. X‐ray crystal‐structure analysis of an intermediate homoleptic alkoxide Mn^III complex shows tridentate binding of the ligand via the two pyridyl groups and the newly installed alkoxide moiety, with the oxime group no longer coordinated. The structure of a Mn^II complex of the final ketone ligand, cis‐[MnBr₂(hidpe)₂] (hidpe=2‐(hydroxyimino)‐1,2‐di(pyridine‐2‐yl)ethanone) shows that bidentate oxime/pyridine coordination has been resumed. H₂¹⁸O and ¹⁸O₂ labeling experiments suggest that the inserted O atoms originate from two different O₂ molecules. The progress of the oxygenation was monitored through changes in the resonance‐enhanced Raman bands of the oxime unit.     

A dinuclear zinc complex containing a diamond‐core geometry: [Zn2(μ2‐GueO)2(GueO)2(py)2]·0.5(toluene) (GueOH is guethol)

The title zinc alkoxide, bis(μ‐2‐ethoxyphenolato)‐κ³O¹,O²:O¹;κ³O¹:O¹,O²‐bis[(2‐ethoxyphenolato‐κ²O¹,O²)(pyridine‐κN)zinc(II)] toluene hemisolvate, [Zn₂(C₈H₉O₂)₄(C₅H₅N)₂]·0.5C₇H₈, crystallizes with two independent complex molecules located on inversion centres and one independent toluene solvent molecule disordered about an inversion centre. The Zn^II atoms are six‐coordinated in distorted octahedral geometries with O₅N donor sets. The Zn^II ions and bridging alkoxide groups are arranged in a diamond Zn₂O₂ core structure. The guetholate (2‐ethoxyphenolate) ligands adopt two different coordination modes, viz. peripheral chelating and μ₂‐bridging. Preliminary investigations of the catalytic activity of the compound in the ring‐opening polymerization of L‐lactide demonstrate rapid and efficient generation of polylactide.     

Disproportionation of hydrogen peroxide in the presence of Mn(III) complexes with various porphyrins and acid anions

The kinetics of homogeneous decomposition of H₂O₂ in the presence of Mn(III) complexes with octaethylporphine or meso-phenyloctaethylporphines and acid anions Cl^?, AcO^?, and SCN^? was studied by volumetry. The ionic-molecular mechanism of the transformation, involving reversible coordination of the H₂O₂ molecule, its irreversible decomposition with the release of H₂O and removal of two electrons from the metal porphyrin, reversible coordination of the second peroxide molecule in the form of HO ₂ ^? , and slow irreversible reduction of the catalyst with the release of O₂ and H₂O was substantiated by electronic absorption spectra. The catalytic activity of Mn(III) porphyrin complexes is independent of the acid anion present as extra ligand, but depends on the structure of the porphyrin ligand, which can be used for controlling the catalytic activity. Unsymmetrical (chloro)(monophenyloctaethylporphinato)managanese(III) is the most active; it increases the rate of O₂ evolution by a factor of 2 at the peroxide: catalyst molar ratio of (3 × 10⁵): 1.     

A polymeric cobalt(II) complex derived from citric acid (H4cit) and 2,6‐diaminopurine (dap): {[Co4(cit)2(dap)4(H2O)4]·6.35H2O}n

Poly[[tetraaquadi‐μ₄‐citrato‐tetrakis(2,6‐diaminopurine)tetracobalt(II)] 6.35‐hydrate], {[Co₄(C₆H₄O₇)₂(C₅H₆N₆)₄(H₂O)₄]·6.35H₂O}_n, presents three different types of Co^II cations in the asymmetric unit, two of them lying on symmetry elements (one on an inversion centre and the other on a twofold axis). The main fragment is further composed of one fully deprotonated citrate (cit) tetraanion, two 2,6‐diaminopurine (dap) molecules and two aqua ligands. The structure is completed by a mixture of fully occupied and disordered solvent water molecules. The two independent dap ligands are neutral and the cit tetraanion provides for charge balance, compensating the 4+ cationic charge. There are two well defined coordination geometries in the structure. The simplest is mononuclear, with the Co^II cation arranged in a regular centrosymmetric octahedral array, coordinated by two aqua ligands, two dap ligands and two O atoms from the β‐carboxylate groups of the bridging cit tetraanions. The second, more complex, group is trinuclear, bisected by a twofold axis, with the metal centres coordinated by two cit tetraanions through their α‐ and β‐carboxylate and α‐hydroxy groups, and by two dap ligands bridging through one of their pyridine and one of their imidazole N atoms. The resulting coordination geometry around each metal centre is distorted octahedral. Both groups are linked alternately to each other, defining parallel chains along [201], laterally interleaved and well connected via hydrogen bonding to form a strongly coupled three‐dimensional network. The compound presents a novel μ₄‐κ⁵O:O,O′:O′,O′′,O′′′:O′′′′ mode of coordination of the cit tetraanion.