Preparation and characterization of manganese(III) halide derivatives of N,N′-bis(aminobenzylidene)-1,2-ethanediamine

The preparation and characterization of manganese(III) complexes containing the quadridenate ligand, N,N′-bis(aminobenzylidene)-1,2-ethanediamine (H₂amben), and its previously unreported analogue, N,N′-bis(2-amino-5-nitro-benzylidene)-1,2-ethanediamine (H₂nitroamben), are described. The new manganese(III) halide/pseudohalide complexes, Mn(amben)X · nH₂O and Mn(nitroamben)X · nH₂O (X = Cl, Br, I, NCS; n =  0.5 or 1), were isolated as red-brown, microcrystalline solids, which were characterized fully.     

Synthesis, characterization and crystal structure of manganese (IV) complex derived from salicylic acid

The binuclear manganese (IV) [Mn₂(Hsal)₄(OH)₄] (H₂sal = salicylic acid) complex has been obtained from a complex reaction mixture in methanol consisting of Mn(II)(OAc)₂ · 4H₂O, GS ( a reagent obtained by refluxing glycine and salicylaldehyde in 1:1 molar ratio in methanol), monosodium salicylate and pyridine. The compound contains a distorted octahedral MnO₆ coordination unit of potential importance to high oxidation state manganese bimolecules.     

Monomeric versus dimeric structures in ternary complexes of manganese(II) with derivatives of benzoic acid and nitrogenous bases: structural details and spectral properties

Adducts formed by [Mn(2,6-dmb)₂(H₂O)₃]_n · nH₂O, 2,6-dmb=2,6-dimethoxybenzoate(1-), Mn(2,4-dhb)₂ · 8H₂O, Mn(2,5-dhb)₂ · 4H₂O or Mn(2,6-dhb)₂ · 8H₂O, dhb=dihydroxybenzoate(1-), and 2,2^′-bipyridine (bpy), 4,4^′-dimethyl-2,2^′-bipyridine (Me₂bpy) or 4,7-dimethyl-1,10-phenanthroline (Me₂phen) were isolated in the solid state and characterised by IR, EPR and thermogravimetry. Two of them, [Mn(2,6-dhb)₂(bpy)₂] (1) and [Mn₂(2,6-dmb)₄(Me₂Phen)₂(H₂O)₂] · 2EtOH (2), were studied by single crystal X-ray diffraction. The adduct 1 is mononuclear and consists of hexa-co-ordinate manganese(II) ions bound to two bipyridine and two 2,6-dihydroxybenzoate ligands in a cis-octahedral arrangement. The complex 2 exhibits a dinuclear structure in which two manganese(II) ions share two carboxylate groups adopting a rather uncommon single-atom bridging mode. The results allow us to conclude that weak, e.g., hydrogen bonding and stacking interactions govern the type of structure, monomeric or dimeric. The spectral features of the complexes are discussed. In particular, the solid-state EPR features of the complexes are interpreted in terms of D, E and H_max, the high-field resonance. For the monomeric species, the higher is the D value, the higher is H_max.     

Behaviour of iron and manganese chelates in calcareous soils and their effectiveness for plants

Summary The behaviour of the metal chelates Mn-EDTA, Mn-DTPA, Mn-EDDHA, Fe-EDTA, Fe-DTPA and Fe-EDDHA in calcareous soils and their availability to plants were studied. The effectiveness of a metal chelate was shown to depend on its stability, the fixation capacity in the soil and its toxicity to the plant. Incorporation of Fe-DTPA into a framework of silica molecules prevents the fixation of Fe-DTPA in the soil. Fe-DTPA and Fe-EDDHA cause a reduction in the manganese uptake of the plant. The most striking result was the behaviour of Mn-DTPA in calcareous soils. Partial replacement of manganese in the chelate by iron from the soil makes this chelate useful for supplying the plant with both iron and manganese. Mn-DTPA appears to be the ideal type of chelate for the correction of chlorosis in the Netherlands, but unfortunately is not yet commercially available.     

Pseudohalide complexation by manganese 12-metallacrowns-4 complexes

The reaction of manganese chloride, sodium or potassium thiocyanate and salicylhydroxamic acid in dimethylformamide-methanol solution leads to the formation of the 12-membered metallacrowns [Na(dmf)₂]₂(SCN)₂{[12-MC_{Mn(III)N(shi)}-4](dmf)₄} (1) and [K(dmf)₂]₂(SCN)₂{[12-MC_{Mn(III)N(shi)}-4](dmf)₄} (2). The crystal structure analyses of 1 and 2 show that pseudohalide ligands are bound to the ring manganese ions through the N atoms, while the alkaline ions, Na⁺ or K⁺, are accommodated at the cavity of the metallacrown ring. The alkali cations are bound to four oxygen atoms of the metallacrown ring and a single axial dmf. The binding of the pseudohalides (SCN⁻, OCN⁻ and N₃⁻) to the manganese ions of the metallacrown ring is very similar to that observed previously for (NaBr)₂ and (KBr)₂ metallacrowns; however, unlike the previously described halide complexes, the thiocyante does not form a bridge between the ring and central metal ions. Furthermore, the pseudohalide ligands do not form a second bond to an adjacent metallacrown, thus, single metallacrowns are isolated rather than chains or columns. The affinity of thiocyanate for the metallacrown is approximately equal to chloride and significantly greater than bromide.     

Temperature effect on the conversions of phthalato and maleato manganese(II) complexes with diamine ligands

1,10-Phenanthroline hydrogen phthalato manganese(II) dimer [Mn₂(Hphth)₂(phen)₄] · 2Hphth · 6H₂O (1), monomeric phenanthroline phthalato manganese(II) monomer [Mn(phth)(phen)₂(H₂O)] · 2.5H₂O (2), 2,2′-bipyridine phthalato manganese(II) polymer [Mn(phth)(bpy)(H₂O)₂]_n (3) and 1,10-phenanthroline maleato polymer [Mn(male)(phen)(H₂O)₂]_n · 2nH₂O (4) (H₂phth = o-phthalic acid, male = maleic acid, phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine) have been synthesized and characterized spectroscopically and structurally. Each Mn(II) atom in dimeric 1 is octahedrally coordinated by two oxygen atoms of phthalate anions and by two cis-phenanthroline ligands. The hydrogen phthalato anion bridges the Mn(II) ions through the deprotonated carboxyl groups, while the carboxylic acid group remains free. In the monomeric 2, the Mn(II) ion is octahedrally surrounded by four nitrogen atoms from two cis-phen ligands, one carboxyl oxygen from a monodentate phth ion, and one coordinated water molecule. The dimeric phthalato complex 1 can be cleaved into monomer 2 under heating with deprotonation, and the course of the reaction can be qualitatively traced by IR spectra. The phthalate group in the complex 3 binds to two manganese atoms through the vicinal carboxyl-oxygen atoms in syn-syn bridging mode. The Mn(II) atoms are linked by the phthalate group to yield a one-dimensional chain running along the a-axis. The coordination polymer 3 can be obtained from the reaction of dichloro dibipyridine manganese with phthalate under heating. In polymer 4, the manganese atom is six-coordinated by two nitrogen atoms from phen, two oxygen atoms from the coordinated water molecules and two oxygen atoms from two different maleate dianions. Each maleato unit links two neighboring manganese atoms to yield one-dimensional chain along b-axis in bis-monodentate mode. The single-chain polymer 4 prepared at low temperature can be converted to double-chain coordination polymer [Mn(male)(phen)]_n · nH₂O (5) with dehydration in warm solution.     

Mono- and dinuclear manganese(II) complexes derived from the cis/trans isomers of 2,4,5-tris(2-pyridyl)-4,5-dihydroimidazole

Two new manganese(II) complexes, [Mn(L1)(L1H)(ClO₄)(H₂O)][ClO₄]₂·0.5CH₃CN·H₂O (1) [L1 = trans-(±)2-(2,5-di(pyridin-2-yl)-4,5-dihydro-1H-imidazol-4-yl)pyridine)] and [Mn₂(μ-L2)₂(H₂O)₃(CH₃CN)₃][ClO₄]₄·2CH₃CN (2) [L2 = cis-(±)2-(2,5-di(pyridin-2-yl)-4,5-dihydro-1H-imidazol-4-yl)pyridine)], have been prepared and examined by single-crystal X-ray diffraction analysis, showing that complex 1 is a mononuclear compound, whereas complex 2 is a dinuclear species. The cis/trans isomers L1 and L2 have similar coordination properties, but behave as bidentate and tridentate chelating ligands, respectively, giving distorted octahedral metal coordination geometries. X-ray diffraction studies revealed that the molecular and crystal structures are stabilized by a series of intra- and intermolecular interactions. In both cases extended supramolecular networks are generated, in compound 1 through O-H···O, O-H···N, N-H···O, N-H···N, C-H···O, C-H···N, C-H···π and π···π interactions, and in compound 2 through O-H···O, O-H···N, C-H···O and π···π interactions. The observed structural differences between the two metal complexes might be a consequence of these stabilizing effects.     

Structural studies on manganese(III) and manganese(IV) complexes of tetrachlorocatechol and the catalytic reduction of dioxygen to hydrogen peroxide

The mononuclear complexes (Bu₄N)[Mn(Cl₄Cat)₂(H₂O)(EtOH)] and (Bu₄N)₂[Mn(Cl₄Cat)₃] (H₂Cat=1,2-dihydroxybenzene) have been synthesised and characterised by X-ray diffraction. This work provides a direct, independent, synthesis of these complexes and an interesting example of how solvent effects can promote the formation of either a manganese(III) or manganese(IV) complex of the same ligand. The characterisation of (Bu₄N)[Mn(Cl₄Cat)₂(H₂O)(EtOH)] supports previous work that manganese(III) is extremely reluctant to form tris (catecholato) complexes due to the short `bite distance' of catecholate oxygen atoms (2.79 Å) which are unable to span the elongated coordination axes of the Jahn-Teller distorted Mn(III) ion and explains the 2:1 and 3:1 tetrachlorocatechol:manganese ratios in the Mn(III) and Mn(IV) complexes, respectively. Hydrogen peroxide production using dioxygen and hydroxylamine as substrates in acetonitrile/water mixtures, under ambient conditions, can be demonstrated with both complexes, suggesting that neither labile coordination sites nor the oxidation state of the manganese are important to the catalytic system. Turn over frequencies (TOF, moles of H₂O₂ per moles of manganese per hour) of ∼10 000 h⁻¹ are obtained and this compares very favourably with the commercial production of hydrogen peroxide by the autoxidation of 2-ethylanthrahydroquinone (AO process).     

Synthesis, crystal structures and luminescent properties of zinc and manganese complexes from Demko-Sharpless reaction

The synthesis and crystal structure of two new complexes (Zn and Mn) containing tetrazolyl ligands are described. In situ [2+3] cycloaddition reactions of fipronil, (fipronil = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-carbonitrile) with sodium azide in the presence of ZnCl₂ or MnCl₂ as a Lewis acid (Demko-Sharpless tetrazole synthesis method) under hydrothermal (solvothermal) reaction conditions gave [Zn(L)₂](H₂O)₂] · H₂O, 1 and [Mn(L)₂](H₂O)₂] · H₂O, 2, (HL = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-tetrazole). The central metals in both complexes are six coordinated, which connected by two water molecules, two nitrogen atoms from different tetrazolyl groups and two nitrogen atoms from pyrazolyl rings respectively. Photoluminescence studies reveal that both title complexes exhibit strong blue fluorescent emissions at λ_max = 383 nm for 1 and 411 nm for 2 respectively in the solid state at room temperature.     

Bleaching of Hardwood Kraft Pulp with Manganese Peroxidase Secreted from Phanerochaete sordida YK-624

In vitro bleaching of an unbleached hardwood kraft pulp was performed with manganese peroxidase (MnP) from the fungus Phanerochaete sordida YK-624. When the kraft pulp was treated with partially purified MnP in the presence of MnSO₄, Tween 80, and sodium malonate with continuous addition of H₂O₂ at 37°C for 24 h, the pulp brightness increased by about 10 points and the kappa number decreased by about 6 points compared with untreated pulp. The pulp brightness was also increased by 43 points to 75.5% by multiple (six) treatments with MnP combined with alkaline extraction. Our results indicate that in vitro degradation of residual lignin in hardwood kraft pulp with MnP is possible.     

Epoxide ring opening in a zinc(II) complex in water without any Lewis acid catalyst: Formation of only one diastereomer out of 2

The epoxide ring in 5,6-dihydro-5,6-epoxy-1,10-phenanthroline (L) opens up in its reaction with 4-methylaniline and 4-methoxyaniline in water in equimolar proportion at room temperature without any Lewis acid catalyst to give a monohydrate of 6-(4-methyl-phenylamino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L′·H₂O) and 6-(4-methoxyphenyl-amino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L″) respectively. Reaction time decreases from 72 to 14 h in boiling water. But the yields become less. Reaction of L with Zn(ClO₄)₂·6H₂O in methanol in 3:1 molar ratio at room temperature affords white [ZnL₃](ClO₄)₂·H₂O. The X-ray crystal structure of the acetonitrile solvate [ZnL₃](ClO₄)₂·MeCN has been determined which shows that the metal has a distorted octahedral N₆ coordination sphere. [ZnL₃](ClO₄)₂·2H₂O reacts with 4-methylaniline and 4-methoxyaniline in boiling water in 1:3 molar proportion in the absence of any Lewis acid catalyst to produce [ZnL′₃](ClO₄)₂·4H₂O and [ZnL″₃](ClO₄)₂·H₂O, respectively in 1-4 h time in somewhat low yield. In the ¹H NMR spectra of [ZnL′₃](ClO₄)₂·4H₂O and [ZnL″₃](ClO₄)₂·H₂O, only one sharp methyl signal is observed implicating that only one diastereomer out of the 2³ possibilities is formed. The same diastereomers are obtained when L′·H₂O and L″ are reacted directly with Zn(ClO₄)₂·6H₂O in tetrahydrofuran at room temperature in very good yields. Reactions of L′·H₂O and L″ with Ru(phen)₂Cl₂·2H₂O (phen = 1,10-phenanthroline) in equimolar proportion in methanol-water mixture under refluxing condition lead to the isolation of two diastereomers of [Ru(phen)₂L′](ClO₄)₂·2H₂O and [Ru(phen)₂L″](ClO₄)₂·2H₂O.     

Synthesis, crystal structure and magnetic properties of a novel manganese(III) cluster

A polydentate hydroxy-rich Schiff base ligand, derived from the condensation of 3,5-dibromo-2-hydroxybenzaldehyde and 2-ethanolamine, namely 3,5-dibromo- salicylidene-2-ethanolamine (H₂L), reacts with Mn(ClO₄)₂, NaO₂CPiv and NaOCH₃ to give a novel hexanuclear complex [Na^IMn^III₅(μ₃-O²⁻)(μ₄-O²⁻)L₄(O₂CPiv)₃)(ClO₄)]·1.5CH₃OH·0.25H₂O (1). The complex has been characterized by IR, elemental analyses, crystal structural analyses, and magnetic studies. The core in complex 1 features one μ₃-O²⁻ atom, one μ₄-O²⁻ atom, four L²⁻ ligands, three PivCO₂⁻ groups together with a ClO₄⁻ ion bridging five Mn^III atoms and a Na^I atom to form a distorted cubane extended at one face by an incomplete adamantane unit, which is an unprecedented structural type in Mn chemistry. The variable-temperature solid-state dc magnetic susceptibility studies in the 2-300 K range for complex 1 reveal the presence of overall antiferromagnetic intracluster interactions.     

Synthesis, structure and magnetic properties of a two-dimensional manganese(II) complex with a maximum denticity of ethylenediaminetetraacetic ligand

A new Mn(II) complex, [Mn₂(edta)(H₂O)]_n·nH₂O (1) (H₄edta = ethylenediaminetetraacetic acid) has been synthesized by the reaction of MnCl₂·4H₂O and H₄edta under hydrothermal conditions, and was characterized by single-crystal X-ray diffraction study, variable temperature (1.8-300 K) magnetic measurement, and thermal gravity analysis. The result of X-ray crystallographic analysis reveals that complex 1 is the first two-dimensional (2D) Mn-edta coordination polymer with a grid-like (4,4)-topology, which is built from Mn-carboxylate chains and entirely deprotonated edta⁴⁻ ligands with a maximum denticity. The variable temperature magnetic data indicate that complex 1 exhibits strong antiferromagnetic couplings.     

Bauxite residue sand has the capacity to rapidly decrease availability of added manganese

Bauxite residue sand, even though a poor substrate for plant growth because of very high pH, salinity and sodicity, is required to be revegetated. Manganese deficiency is observed in residue-grown plants because broadcast applications of manganese fertiliser to the surface of residue deposits have a low residual value. In a laboratory experiment, manganese (as MnSO₄) was added to fresh and 4-year-old residue sand and a sequential fractionation procedure performed at 0, 1, 4, 8 and 24 h and 6, 14, 21, 43, 73, 103 and 130 d. Extraction with DTPA estimated plant-available Mn, while sequential fractionation with various extractants yielded the following fractions: readily soluble [Ca(NO₃)₂]; weakly adsorbed [CaDTPA-B₄O₇]; carbonate-bound [HNO₃]; and oxide-bound [NH₂OHHCl]. Residual Mn was calculated as a difference between the sum of all these forms and total Mn in residue sand. Transformation of manganese from the initially dominant readily soluble form to the less-available forms was very rapid (< 24 h). A change to fertilisation strategies is required if better efficiency of manganese application and uptake is to be achieved for plants growing on bauxite residue.     

Synthesis and spectral investigation of manganese(II), cadmium(II) and oxovanadium(IV) complexes with 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone): Crystal structure of manganese(II) and cadmium(II) complexes

The chelating behavior of 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone) (H₂dapa) towards manganese(II), cadmium(II) and oxovanadium(IV) ions has been studied by elemental analyses, conductance measurements, magnetic properties and spectral (IR, ¹H NMR, UV-Vis and EPR) studies. The IR spectral studies suggest the pentadentate nature of the ligand with pyridine nitrogen, two azomethine nitrogens and two carbonyl oxygen atoms as the ligating sites. Six coordinate structure for [VO(H₂dapa)]SO₄ · H₂O and seven coordinate structures for [Mn(H₂dapa)(Cl)(H₂O)]Cl · 2H₂O and [Cd(H₂dapa)Cl₂] · H₂O complexes have been proposed. Pentagonal bipyramidal geometry for [Mn(H₂dapa)(Cl)(H₂O)]Cl · 2H₂O and [Cd(H₂dapa)(Cl₂)] · H₂O complexes was confirmed by single crystal analysis. The X-band EPR spectra of the oxovanadium(IV) and manganese(II) complexes in the polycrystalline state at room (300 K) and also at liquid nitrogen temperature (77 K) were recorded and their salient features are reported.     

Synthesis, crystal structures and luminescent properties of manganese and zinc complexes with in situ ligand formation of 3-amino-4-(5-tetrazolyl)-1H-pyrazole

Three metal-organic frameworks, [Mn(HL)(N₃)] (1), [Mn(HL)Cl(H₂O)] (2) and [Zn₂(L)₂(H₂O)] (3) where H₂L = 3-amino-4-(5-tetrazolyl)-1H-pyrazole, have been yielded through in situ hydrothermal reactions of manganese(II) or zinc(II) salts, NaN₃ and 3-amino-4-cyano-1H-pyrazole (HACP). The crystal structure analysis reveals that 1-3 have different dense 3D frameworks with Schläfli symbols of {3·4²·5²·6}{3²·4³·5⁴·6⁶} for 1 which is an unprecedented (4,6)-connected framework, {4·12²}2{4²·12⁴} for 2 which is a typical sqc519 structure, and {4²·6}2{4⁴·6²·8⁸·10} for 3 which is a typical ant/anatase structure, respectively. The ligand takes three different coordination modes in 1-3 as 3- or 4-connector. In addition, the photoluminescence of complex 3 was studied in solid state at room temperature, together with its thermal analysis.     

Effect of seed manganese content on the growth of wheat (triticum aestivum) under manganese deficiency

Summary The importance of seed manganese (Mn) content for seedling growth of two wheat cultivars under soil Mn deficiency was demonstrated in growth cabinet experiments. Seed was obtained from different field sites (giving a Mn content range of 0.1 to 6.4 μg Mn seed⁻¹), as well as from soaking seed in MnSO₄ prior to sowing. Seed soaking greatly increased the seed Mn content, however, only about 15–20% of this additional Mn was recovered in the seedlings after 26 days growth. In these experiments, the seed rather than the soil provided the major source of plant Mn. Manganese critical deficiency levels (CDLs) were also obtained for leaves, shoots and roots. Increased grain yields from seed soaking were also evident in the field.     

Medium optimization for a methanol utilizing bacterium based on chemostat theory

Summary In the productions of biomass and vitamin B₁₂ using methanol as the sole carbon source, it is necessary to use a medium in which methanol is the growth limiting substrate. Other inorganic salts should be in slight excess so that the yield of cells and the intracellular content of vitamin B₁₂ do not vary. From basic principles of chemostat culture, a medium was optimized for Pseudomonas AM-1 a methanol utilizing bacterium, for the concentrations of various inorganic salts. This was done in a series of chemostat cultures at a dilution rate of 0.1 h^–1. Optimum amounts of NH₄ ⁺, PO₄ ^3- and Mg²⁺ were estimated from the minimum concentration of the salt at which methanol became growth limiting. The optimum concentrations of Ca²⁺, Fe²⁺, Mn²⁺, and Zn²⁺ as a group were determined in the same way. Cu²⁺, Mo⁶⁺, Co²⁺ and B³⁺ are required at concentrations of g/l and they were not studied as these very low level can be introduced as contaminants from other salts. The optimum medium composition (in g/l) was as follows: (NH₄)₂SO₄, 1.0; H₃PO₄, 75×10^–3; MgSO₄ · 7H₂O, 30×10^–3; CaCl₂ · 2H₂O, 3.3×10^–3; FeSO₄ · 7H₂O, 1.3×10^–3, MnSO₄ · 4H₂O, 0.13×10^–3; ZnSO₄ · 7H₂O, 0.13×10^–3; CuSO₄ · 5H₂O, 40×10^–6; Na₂MoO₄, 40×10^–6; CoCl₂ · 6H₂O, 40×10^–6; H₃BO₃, 30×10^–6 and methanol 4.     

Effects of nitrogen on properties of oxyfluoronitride bioglasses

Bioglasses are used as bone substitutes and prosthetic coatings. Following implantation, they are predisposed to generate a series of physicochemical reactions at the glass-bone interface. Bioglasses with molar composition: 55SiO₂–8.5CaO–31.5Na₂O–5CaF₂ have been synthesized and characterized. However, because of their poor strength, doping with nitrogen was performed on these glasses to increase their mechanical properties. These glasses were chemically analyzed to verify the amount of nitrogen introduced and structurally characterized by ²⁹Si and ¹⁹F MAS NMR. The fluorine complexes with calcium and sodium and is present as mixed calcium sodium fluoride and sodium fluoride species. The addition of fluorine to bioglasses reduces the melting temperature which helps to minimize nitrogen loss and bubble formation. So the fluorine facilitates the dissolution of nitrogen into the melt. Nitrogen substitutes for oxygen in the silicate network and is present as SiO₃N and SiO₂N₂ structural units. The density, glass transition temperature, Young's modulus, hardness and fracture toughness all increase with the content of nitrogen introduced into the glasses. These changes are a result of greater cross-linking of the silicate network due to the higher coordination of nitrogen compared to oxygen.     

Manganese (III) cyclam complexes with aqua, iodo, nitrito, perchlorato and acetic acid/acetato axial ligands

The syntheses, structures and magnetic properties of five new manganese (III) cyclam complexes, trans-[Mn(cyclam)(OH₂)₂](CF₃SO₃)₃ · H₂O, trans-[Mn(cyclam)I₂]I, trans-[Mn(cyclam)(ONO)₂]ClO₄, trans-[Mn(cyclam)(OClO₃)₂]ClO₄ and trans-[Mn(cyclam)(CH₃COO)(CH₃COOH)](ClO₄)₂, are reported. Cyclam is the tetradentate amine ligand 1,4,8,11-tetraazacyclotetradecane. The complexes all exhibit pronounced tetragonal elongation of the coordination octahedron with the four cyclam nitrogens occupying the four equatorial positions. The magnetic properties are consistent with the formulation of the complexes as high-spin d⁴ systems. trans-[Mn(cyclam)(OH₂)₂](CF₃SO₃)₃ · H₂O is shown to be a convenient starting material for the syntheses of trans cyclam complexes. [Mn(cyclam)(CH₃COO)(CH₃COOH)](ClO₄)₂ exhibits extremely short intermolecular hydrogen bonds resulting in a pseudo-chain structure. The tilt of the axial ligands with respect to the equatorial plane containing the manganese and the cyclam nitrogen atoms is discussed.