A BENT MIXED-VALENCE MANGANESE(III/II/III) COMPLEX - A NEW CLASS OF TRINUCLEAR, ACETATE BRIDGED SCHIFFS BASE COMPOUNDS EXHIBITING A G = 2 MULTILINE ESR SIGNAL

The e.s.r. spectrum of the bent mixed valence Mn(III/II/III) (saladhp) 2(OAc)4(MeOH)2[saladhp = 2-(salicylideneaminato)- 1,3-dihydroxy-2-methylpropane] in dimethylformamide provides the observation of a multiline e.s.r. signal from a trinuclear mixed-valence manganese complex and allows for the comparison of magnetic and spectroscopic properties of related models for the photosynthetic water oxidizing enzymeclose50

STRUCTURALLY DIVERSE MANGANESE(III) SCHIFF-BASE COMPLEXES - CHAINS, DIMERS, AND CAGES

Manganese(III) forms a rich variety of complexes with the dianion of the Schiff base ligand N,N???-disalicylidene-2-hydroxypropylenediamine (2-OH-SALPN) and its ring-substituted derivatives. Single crystals of [Mn(2-OH-SALPN)OAc] n (1) are isolated when manganese(III) acetate is reacted with 2-OH-SALPN, in DMF. This infinite chain shows an anti-anti configuration for the bridging acetates. When 1 is dissolved in methanol and 1 equiv of NaOH is added, a dinuclear [Mn III 2(2-OH-SALPN) 2(CH 3OH)]??CH 3OH complex, 3, is isolated. X-ray analysis of crystals of the 5-chloro-2-OH-SALPN derivative 4 show this compound to be a monoalkoxy-bridged species with the longest Mn(III)-Mn(III) separation (3.808 A) yet observed for a discrete single-atom-bridged dimer. If NaOMe is used as a base rather than NaOH, the first example of a totally encapsulated tetrakis(phenolato)-bis(acetato)-caged sodium cation, 5, is isolated. Two Mn III(2-OH-SALPN) units are linked by this sodium ion, forming a bimetallic, trinuclear cluster. The variable-temperature magnetic behavior of these materials shows that spin exchange between the manganese ions is weak or nonexistent [1, J = -1.72 cm -1 and g = 1.97; 4, J = -3.55 cm -1 and g = 1.95; 5, follows Curie-Weiss law behavior with no evident spin exchange between Mn(III) ions (g ??? = 2.00, g ??? = 2.05, D = -6.13 cm -1)]. X-ray crystallographic parameters: 1, C 19H 19N 2O 5Mn, mol wt 410.3, orthorhombic crystal system (Pnma), a = 6.528 (4) A, b = 16.827 (6) A, c= 16.754 (6) A, V = 1840 (1) A 3, Z = 4, 2054 data collected with 0?? < 2?? < 50??, 1180 data with I > 3??(I), R = 0.057, R w = 0.057; 4, C 36H 34N 4O 8Mn 2Cl 4, mol wt 900, monoclinic crystal system (P2 1/c), a = 10.944 (2) A, b = 23.275 (5) A, c = 16.047 (2) A, ?? = 99.29 (1)??, V = 4034 (1) A 3, Z = 4, 5315 data collected with 0?? < 2?? < 45??, 3247 data with I > 2??(I), R = 0.057, R w = 0.045; 5, C 44H 55N 4O 18Mn 2Na, mol wt 1060, triclinic crystal system (P1), a = 9.434 (5) A, b = 10.436 (4) A, c = 12.758 (8) A, ?? = 94.42 (4)??, ?? = 105.50 (4)??, ?? = 91.50 (4)??, V = 1205 (1) A 3, Z = 1, 3174 data collected with 0?? < 2?? < 45??, 2445 data with I > 3??(I), R = 0.068, R w = 0.068.close1439

CATIONIC CONTROL OF SPIN DIMENSIONALITY IN INFINITE CHAINS OF (CATION)2[MNIII(SALICYLATE)2(CH3OH)2][MNIII(SALICYLATE)2]

X-ray structure analysis demonstrates that alternating AB type chains of general composition (cat)2[MnIII(sal)2(CH3OH) 2]-[MnIII(sal)2] [cat = Na+ (1), K+ (2), NH4 + (3); sal = salicylate] can be prepared by the reaction of MnCl2 with salicylic acid and the appropriate base. The molecular structures are composed of three parts: (i) the polyhedron of Mn1 in MnIII(sal)2(CH3OH)2 (the A unit), (ii) the polyhedron of Mn2 in MnIII(sal)2 (the B unit), which is bridged to the A structure by two carboxylates, and (iii) the monovalent cation coordination environment. Varying the cation causes increases in Mn1-Mn2 separations (Na+, 5.347 A; K+, 5.520 A; NH4 +, 5.561 A) and relative tilting of the tetragonal planes of the two metals [Mn2-O3-C7 angles: Na+, 134.3 (4)??; K+, 139.8 (3)??; NH4 +, 140.3 (2)??]. Variable-temperature magnetic susceptibilities of 1-3 were measured to determine the type and magnitude of magnetic exchange in these S = 2 chains. The exchange interaction is weakly antiferromagnetic, with all three salts behaving as one-dimensional magnets and the Na+ salt showing three-dimensional exchange. The observations are rationalized by a spin-exchange model. Crystal data are as follows. 1: triclinic, P1, a = 7.725 (2) A, b = 10.596 (3) A, c = 12.892 (3) A, ?? = 102.75 (2)??, ?? = 104.64 (2)??, ?? = 110.59 (2)??, Z = 1, V = 898.2 (4) A3; for 2366 data collected in the range 3 ??? 2?? ??? 45?? and 1791 data with I > 3??(I), R = 0.056 (Rw = 0.060). 2: triclinic, P1, a = 8.060 (3) A, b = 10.784 (3) A, c = 12.778 (3) A, ?? = 103.40 (2)??, ?? = 104.15 (2)??, ?? = 109.96 (2)??, Z = 1, V = 949.8 (5) A3; for 2497 data collected in the range 3 ??? 2?? ??? 45?? and 1885 data with I > 3??(I), R = 0.035 (Rw = 0.034). 3: triclinic, P1, a = 8.246 (3) A, b = 10.805 (3) A, c = 13.080 (4) A, ?? = 68.42 (2)??, ?? = 96.80 (3)??, ?? = 69.97 (3)??, Z = 1, V = 977.6 (6) A3; for 2534 data collected in the range 3 ??? 2?? ??? 45?? and 2180 data with I > 3??(I), R = 0.030 (Rw = 0.031).close382

STRUCTURAL AND MAGNETIC CHARACTERIZATION OF TRINUCLEAR, MIXED-VALENCE MANGANESE ACETATES

Four mixed valence, trinuclear manganese complexes of general stoichiometry MnIIMnIII 2L2(carboxylate) 4X2, where L is a tridentate Schiff base ligand and X is a neutral monodentate donor, have been structurally characterized by using X-ray crystallography. The solid-state magnetic behavior of these compounds and two additional isostructural complexes are defined by examining the variable-temperature magnetic susceptibilities of each compound. The structurally characterized complexes have strictly 180?? Mn(III)-Mn(II)-Mn(III) angles as required by crystallographic inversion symmetry. These linear complexes, ??-Mn3(SALADHP)2(acetate)4(CH 3OH)2 (1), ??-Mn3-(SALADHP)2(acetate)4(H 2O)2 (2), ??-Mn3(SALATHM)2(acetate)(CH3OH) 2 (3), and ??-Mn3(SALADHP)2-(acetate)4(HpyrO) 2 (4) (where H2SALADHP = 1,3-dihydroxy-2-methyl-2-(salicylideneamino)propane, H2SALATHM = tris(hydroxymethyl)(salicylideneamino)methane and HpyrO = 1-aza-2-keto-3,5-cyclohexadiene), are distinguished from the previously reported bent isomer ??-Mn3(SALADHP)2(acetate)4(CH 3OH)2 (5). The complexes are valence trapped with two terminal Mn(III) ions showing Jahn-Teller distortions along the carboxylate-Mn(III)-X axis. The manganese separations range from 3.42-3.55 A. This is the first homologous series of mixed-valence complexes that can be used to investigate magnetostructural relationships within manganese clusters. All of the complexes have S = 3/2 ground states with J12 ≈ -3 to -7 cm-1, J11??? ≈ 0 cm-1, zj???, ≈ 0.3 cm-1, g1 ≈ 2.04, and g2 fixed at 2.0. Thus, the antiferromagnetic exchange in these complexes is insensitive to changes in metal-metal distance, metal-metal orientation, acetate bridiging groups, phenolate ring substitution, axial ligation, or Mn(III) out of plane displacement. Crystal data for 1: monoclinic, P21/c, a = 12.450 (3) A, b = 13.504 (4) A, c = 13.428 (5) A, ?? = 102.53 (2)??, V = 2203 (1) A3. For 3420 data collected between 3 ??? 2?? ??? 45?? and 2111 data > 3??(I), the structure refined to R = 0.057 (Rw = 0.055); Z = 2. Crystal data for 2: triclinic, P1, a = 9.459 (10) A, b = 10.524 (6) A, c = 10.965 (10) A, ?? = 109.55 (6)??, ?? = 95.65 (8)??, ?? = 96.53 (7)??, V = 1011 (2) A3,Z = 1. For 2671 data collected between 3 ??? 2?? ??? 45?? and 2010 data > 3??(I), the structure refined to R = 0.041 (Rw = 0.040). Crystal data for 3: triclinic, P1, a = 8.694 (3) A, b = 9.779 (3) A, c = 14.474 (3) A, ?? = 105.53 (2)??, ?? = 104.30 (2)??, ?? = 95.72 (2)??, V = 1130.6 (8) A3, Z = 1. For 3174 data collected between 3 ??? 2?? ??? 45?? and 2321 data > 3??(7) the structure refined to R = 0.041 (Rw = 0.040). Crystal data for 4: triclinic, P1, a = 10.025 (4) A, b = 13.302(8) A, c = 13.380 (7) A, ?? = 114.48 (4)??, ?? = 96.57 (4)??, ?? = 112.33 (4)??, V = 1422 (1) A3, Z = 1. For 3727 data collected between 3 ??? 2?? ??? 40?? and 2502 data > 3??(I), the structure refined to R = 0.057 (Rw = 0.063).close766

Cu-II-herbicide complexes: structure and bioactivity

Copper complexes with the commercial auxin herbicides 2,4-dichlorophenoxy-acetic acid (2,4-D), 3,4-dichlorophenoxy-acetic acid (3,4-D), 2,4,5-trichlorophenoxy-acetic acid (2,4,5-T), 2-methyl-4-chloro-phenoxy-acetic acid (MCPA), 2,3-dichlorophenoxy-acetic acid (2,3-D) and 2-(2,4-dichlorophenoxy)-propanoic acid (2,4-DP) in the presence or not of 2,2′-bipyridine (bipy), an antimicrobial agent, were prepared and characterized. The available evidence supports a dimeric structure for the 2,3-D complex, while the presence of bipy leads to monomeric forms. The solution behaviour of dinuclear complexes in dimethylformamide (DMF) has shown that the complexes are converted to monomeric compounds by the addition of more than 1:2 of bipy. The cyclic voltammograms of dimers in DMF suggest that the complexes retain the dimeric structure in solution. The electron spin resonance spectra of the compound (aqua) (2.2′-bipyridine)bis(2-methyl-4-chloro-phenoxyacetato) copper(II) (1) show features characteristic of the presence of an S = 1 triplet state. The crystal structure of 1 was determined and refined by least-squares methods using three-dimensional Mo Kα data. 1 crystallizes in the space group C2/c, in a cell of dimensions a = 40.49(1), b = 7.286(3). c = 19.617(6) Å, β = 103.23(1)°, V = 5634(3) Å3, Z = 8. Study of the antimicrobial activity showed that the presence of bipy increases the efficiency 4-8 times. © 1998 Elsevier Science S.A. All rights reserved