Herbicides interacting with lanthanide(III) and calcium(II) ions: structural and biological similarities of Gd and Ca polymers.

In this paper we report the synthesis and characterization of Ca(II), Gd(III) and Ce(III) complexes with chlorophenoxyalkanoic acids, which are commonly used as herbicides. The Gd(III) and Ca(II) complexes were characterized by the typical formulas [Gd(III)(L)(3)(H(2)O)(2).2dmf](n) and [Ca(L)(2)(MeOH)(2)](n) [L=[2,4-D=2,4-dichlorophenoxyacetic acid, 2,4,5-T=2,4,5-trichlorophenoxyacetic acid, MCPA=2-methyl-4-chlorophenoxy acetic acid and 2,4-DP=2-(2,4-dichlorophenoxy)propanoic acid]]. The crystal structure of the Gd(III) complex with 2,4-D shows that the compound is a one-dimensional polymer with a [Gd(III)(2)(2,4-D)(6)(H(2)O)(4)] dimeric repeat unit and the gadolinium atoms are in a nine-coordination environment, while the crystal structure of the Ca analog shows that it also has a polymeric structure with a [Ca(2)(2,4-D)(4)(CH(3)OH)(4)] dimeric repeat unit and the calcium atoms are in an eight-coordination environment. The gadolinium compound displays three different coordination modes for the carboxylato moiety, bidentate chelate, bidentate double bound and bidentate triple bound, while the calcium compound displays only one, bidentate triple bound. Coordination spheres are completed with oxygens of H(2)O or MeOH molecules, respectively. The complexes were tested against a few common bacteria by minimum inhibitory concentration (MIC) experiments and did not exhibit any antimicrobial action at concentrations up to 1600 microg/ml.

15-MC-5 manganese metallacrowns hosting herbicide complexes. Structure and bioactivity.

Interaction of manganese with salicylhydroxamic ligands leads to the formation of a series of 15-membered metallacrown Mn(II)(L)(2)[15-MC(Mn(III)N(shi))-5](py)(6) (L=alkanoato ligand). The crystal structure contains a neutral 15-membered metallacrown ring of the type [15-MC(Mn(III)N(shi))-5]. The metallacrown core consists of five Mn(III) and five shi(-3) ligands. The 15-membered metallacrown ring is formed by the succession of five structural moieties of the type [Mn(III)-N-O]. The diversity in the configuration (planar or propeller) for the ring Mn(III) ions gives to the metallacrown core flexibility and simultaneously allows the encapsulation of the sixth Mn(II). The encapsulated Mn(II) is seven-coordinate and is bound to the five hydroximate oxygen donors provided by the metallacrown core, and two oxygen atoms from the carboxylate herbicide ligands. Antibacterial screening data showed that among all the compounds tested, manganese metallacrowns are more active than the simple manganese herbicide or carboxylate complexes while an increase in the efficiency of [15-MC(Mn(III)N(shi))-5] towards the analogous [12-MC(Mn(III)N(shi))-4] can be observed.

NaCeP(2)Se(6), Cu(0.4)Ce(1.2)P(2)Se(6), Ce(4)(P(2)Se(6))(3), and the incommensurately modulated AgCeP(2)Se(6): new selenophosphates featuring the ethane-like [P(2)Se(6)](4-) anion.

NaCeP(2)Se(6), Cu(0.4)Ce(1.2)P(2)Se(6), and AgCeP(2)Se(6) were prepared from nearly stoichiometric proportions of the starting materials plus extra selenium at 750-850 degrees C. Ce(1.33)P(2)Se(6) (or Ce(4)(P(2)Se(6))(3)) was obtained from the same reaction that produced Cu(0.4)Ce(1.2)P(2)Se(6). The structure of all four compounds was determined by single-crystal X-ray diffraction. NaCeP(2)Se(6), Cu(0.4)Ce(1.2)P(2)Se(6), and Ce(1.33)P(2)Se(6) crystallize in the monoclinic space group, P2(1)/c, with a = 12.1422(2), b = 7.6982(1), c = 11.7399(2) A, beta = 111.545(1) degrees and Z = 4 for NaCeP(2)Se(6); a = 12.040(1), b = 7.6418(8), c = 11.700(1) A, beta = 111.269(2) degrees and Z = 4 for Cu(0.4)Ce(1.2)P(2)Se(6); and a = 6.8057(5), b = 22.969(2), c = 11.7226(8) A, beta = 124.096(1) degrees and Z = 6 for Ce(1.33)P(2)Se(6). NaCeP(2)Se(6) has a two-dimensional character and is isostructural to the KLnP(2)Q(6) family of compounds, where Ln = La, Ce, and Pr for Q = Se and Ln = La for Q = S. The structure consists of [CeP(2)Se(6)](n)(n-) layers which are separated by Na(+) cations. Each layer contains CeSe(9) distorted, tricapped trigonal prisms and [P(2)Se(6)](4-) ethane-like anions. Cu(0.4)Ce(1.2)P(2)Se(6) possesses a similar structure; however, substitution of the alkali metal by copper and cerium atoms renders the structure three dimensional. Ce(1.33)P(2)Se(6) is the pure lanthanide member of this structure type. In this three-dimensional structure, there are three cerium metal sites which are partially occupied. The structure of AgCeP(2)Se(6) was solved in the superspace group P2(1)/c(alpha0gamma) and represents an incommensurately modulated version of the KLnP(2)Q(6) structure type, with a = 9.971(5), b = 7.482(3), c = 11.757(4) A, beta = 145.630(9) degrees, q = 0.3121(18)a + 0.4116(19)c, and Z = 2. The structures of the compounds reported here and those of the KLnP(2)Q(6) family are highly related to the monoclinic-II, M(II)PQ(3) structure type (where M = Pb, Sn, Ca, and Sr for Q = S and M = Pb and Sn for Q = Se). Optical and vibrational spectroscopic characterization is also reported.

Impressive structural diversity and polymorphism in the modular compounds ABi3Q5 (A = Rb, Cs; Q = S, Se, Te).

An outstanding example of structural diversity and complexity is found in the compounds with the general formula ABi(3)Q(5) (A = alkali metal; Q = chalcogen). gamma-RbBi(3)S(5) (I), alpha-RbBi(3)Se(5) (II), beta-RbBi(3)Se(5) (III), gamma-RbBi(3)Se(5) (IV), CsBi(3)Se(5) (V), RbBi(3)Se(4)Te (VI), and RbBi(3)Se(3)Te(2) (VII) were synthesized from A(2)Q (A = Rb, Cs; Q = S, Se) and Bi(2)Q(3) (Q = S, Se or Te) at temperatures above 650 degrees C using appropriate reaction protocols. gamma-RbBi(3)S(5) and alpha-RbBi(3)Se(5) have three-dimensional tunnel structures while the rest of the compounds have lamellar structures. gamma-RbBi(3)S(5), gamma-RbBi(3)Se(5), and its isostructural analogues RbBi(3)Se(4)Te and RbBi(3)Se(3)Te(2) crystallize in the orthorhombic space group Pnma with a = 11.744(2) A, b = 4.0519(5) A, c = 21.081(3) A, R1 = 2.9%, wR2 = 6.3% for (I), a = 21.956(7) A, b = 4.136(2) A, c = 12.357(4) A, R1 = 6.2%, wR2 = 13.5% for (IV), and a = 22.018(3) A, b = 4.2217(6) A, c = 12.614(2) A, R1 = 6.2%, wR2 = 10.3% for (VI). gamma-RbBi(3)S(5) has a three-dimensional tunnel structure that differs from the Se analogues. alpha-RbBi(3)Se(5) crystallizes in the monoclinic space group C2/m with a = 36.779(4) A, b = 4.1480(5) A, c = 25.363(3) A, beta = 120.403(2) degrees, R1 = 4.9%, wR2 = 9.9%. beta-RbBi(3)Se(5) and isostructural CsBi(3)Se(5) adopt the space group P2(1)/m with a = 13.537(2) A, b = 4.1431(6) A, c = 21.545(3) A, beta = 91.297(3) degrees, R1 = 4.9%, wR2 = 11.0% for (III) and a = 13.603(3) A, b = 4.1502(8) A, c = 21.639(4) A, beta = 91.435(3) degrees, R1 = 6.1%, wR2 = 13.4% for (V). alpha-RbBi(3)Se(5) is also three-dimensional, whereas beta-RbBi(3)Se(5) and CsBi(3)Se(5) have stepped layers with alkali metal ions found disordered in several trigonal prismatic sites between the layers. In gamma-RbBi(3)Se(5) and RbBi(3)Se(4)Te, the layers consist of Bi(2)Te(3)-type fragments, which are connected in a stepwise manner. In the mixed Se/Te analogue, the Te occupies the chalcogen sites that are on the "surface" of the layers. All compounds are narrow band-gap semiconductors with optical band gaps ranging 0.4-1.0 eV. The thermal stability of all phases was studied, and it was determined that gamma-RbBi(3)Se(5) is more stable than the and alpha- and beta-forms. Electronic band calculations at the density functional theory (DFT) level performed on alpha-, beta-, and gamma-RbBi(3)Se(5) support the presence of indirect band gaps and were used to assess their relative thermodynamic stability.

Computation of aromatic C3N4 networks and synthesis of the molecular precursor N(C3N3)3Cl6.

The successful synthesis and structural characterization of molecules that represent segments of extended solids is a valuable strategy for learning metric and stereochemical characteristics of those solids. This approach has been useful in cases in which the solids are particularly difficult to crystallize and thus their atomic connectivity and overall structures become difficult to deduce with X-ray diffraction techniques. One such class of materials is the covalently linked C(x)N(y) extended solids, where molecular analogues remain largely absent. In particular, structures of C(3)N(4) solids are controversial. This report illustrates the utility of a simple molecule, N(C(3)N(3))(3)Cl(6), in answering the question of whether triazine based C(3)N(4) phases are layered or instead they adopt 3D structures. Here, we present density functional calculations that clearly demonstrate the lower stability of graphitic C(3)N(4) relative to 3D analogues.

One-step synthesis and structure of an oligo(spiro-orthocarbonate).

The reaction of pentaerythritol and tetraethylorthocarbonate at 260 degrees C for 12 h yields a white crystalline material that was characterized by 13C CPMAS NMR, CHN analysis, FT-IR, electron and X-ray powder diffraction, and Rietveld analysis. The white crystalline material was found to have the formula C6H8O4 and a crystal structure with a monoclinic cell [a = 9.167 A, b = 5.681 A, c = 5.880 A, beta = 90.0 degrees , space group I2] of hexagonally arranged spiro-oligomeric chains.