Arpita Jana

Syntheses, Structures, and Magnetic Properties of Diphenoxo-Bridged CuIILnIII and NiII(Low-Spin)LnIII Compounds Derived from a Compartmental Ligand (Ln = Ce−Yb)

Syntheses, characterization, and magnetic properties of a series of diphenoxo-bridged discrete dinuclear M(II)Ln(III) complexes (M = Cu or Ni, Ln = Ce-Yb) derived from the compartmental Schiff base ligand, H(2)L, obtained on condensation of 3-ethoxysalicylaldehyde with trans-1,2-diaminocyclohexane, are described. Single crystal X-ray structures of eight Cu(II)Ln(III) compounds (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Tb (7), Ho (9), Er (10), and Yb (12)) and three Ni(II)Ln(III) (Ln = Ce (13), Sm (16), and Gd (18)) compounds have been determined. Considering the previously reported structure of the Cu(II)Gd(III) (6) compound (Eur. J. Inorg. Chem. 2005, 1500), a total of twelve structures are discussed/compared in this study. Four types of composition are observed in the Cu(II)Ln(III) complexes: [Cu(II)LLn(III) (NO(3))(3)(H(2)O)] (1-3: Ln = Ce-Nd), [Cu(II)LSm(III)(NO(3))(3)]·CH(3)COCH(3) (4), [Cu(II)(H(2)O)LLn(III)(NO(3))(3)] (5: Ln = Eu; 6: Ln = Gd), and [Cu(II)LLn(III)(NO(3))(3)] (4A: Ln = Sm; 7-12: Ln = Tb-Yb). On the other hand, the Ni(II)Ln(III) complexes are characterized to have two types of composition: [Ni(II)LLn(III)(H(2)O)(NO(3))(3)] (13-15: Ln = Ce-Nd) and [Ni(II)LLn(III)(NO(3))(3)]·0.5CH(3)COCH(3) (16-24: Ln = Sm-Yb). Among twelve X-ray structures, seven belong to three different isomorphous sets (Cu(II)Ce(III) (1), Cu(II)Pr(III) (2), Cu(II)Nd(III) (3), and Ni(II)Ce(III) (13); Cu(II)Tb(III) (7), Cu(II)Ho(III) (9), Cu(II)Er(III) (10), and Cu(II)Yb(III) (12); Ni(II)Sm(III) (16) and Ni(II)Gd(III) (18)), whereas space group/unit cell parameters of two others (Cu(II)Sm(III) (4) and Cu(II)Gd(III) (6)) are of different types. The lanthanide(III) centers in Cu(II)Ce(III) (1), Cu(II)Pr(III) (2), Cu(II)Nd(III) (3), and Ni(II)Ce(III) (13) complexes are eleven-coordinated, while the lanthanide(III) centers in other compounds are ten-coordinated. As evidenced from the dihedral angle (δ) between the CuO(phenoxo)(2) and LnO(phenoxo)(2) planes, variation in the extent of planarity of the bridging moiety in the Cu(II)Ln(III) compounds takes place; the ranges of δ values are 0.8-6.2° in the 4f(1-7) analogues and 17.6-19.1° in the 4f(8-13) analogues. The Cu(II)Gd(III) (6) compound exhibits ferromagnetic interaction (Eur. J. Inorg. Chem. 2005, 1500). The nature of the magnetic exchange interaction in the Cu(II)Ln(III) complexes has been understood by utilizing the empirical approach; the Ni(II)Ln(III) complexes have been used as references. The metal centers in the Eu(III) complex are uncorrelated, while other 4f(1-6) analogues (Ce(III), Pr(III), Nd(III), and Sm(III)) exhibit antiferromagnetic interaction. Among the higher analogues (4f(7-13)), only Yb(III) exhibits antiferromagnetic interaction, while interaction in other analogues (Gd(III), Tb(III), Dy(III), Ho(III), Er(III), and Tm(III)) is ferromagnetic. An important aspect of the present study is the measurement of the magnetic susceptibility of the unblocked samples as well as on blocking the samples with grease to avoid powder reorientation, if any. Comparison of the two sets of data reveals significant difference in some cases.

A unique example of a three component cocrystal of metal complexes

The synthesis, characterization and structure of a [3 × 1 + 2 × 1 + 1 × 2] cocrystal [(NiIIL1)2NaI(NO3)]·[{NiIIL1NaI(H2O)2}{NiIIL1}2(NO3)] derived from the hexadentate Schiff base compartmental ligand N,N′-ethylenebis(3-ethoxysalicylaldimine) (H2L1) are described. The compound crystallizes in the monoclinic system (space group C2/c). The structure consists of one trinuclear double-decker [(NiIIL1)2NaI]+ cation, one dinuclear [NiIIL1NaI(H2O)2]+ cation and two mononuclear [NiIIL1] moieties. Each of the two coordinated water molecules of the dinuclear unit is encapsulated in the O4 cavities of the two mononuclear [NiIIL1] moieties resulting in the formation of a tetranuclear self-assembly, which is further interlinked with the trinuclear sandwich species due to Ni⋯Ni interaction to result in an overall one-dimensional topology in the title compound. A unique example of a three component cocrystal of metal complexes, existence of NaI in two entirely different environments in spite of being surrounded by the same blocking ligand and structural resemblance of sodium(I) with 3d metal ions are the major outcomes of the present investigation.

Structures, Magnetochemistry, Spectroscopy, Theoretical Study, and Catechol Oxidase Activity of Dinuclear and Dimer-of-Dinuclear Mixed-Valence MnIIIMnII Complexes Derived from a Macrocyclic Ligand

The work in this paper presents syntheses, characterization, magnetic properties (experimental and density functional theoretical), catecholase activity, and electrospray ionization mass spectroscopic (ESI-MS positive) studies of two mixed-valence dinuclear Mn(III)Mn(II) complexes, [Mn(III)Mn(II)L(μ-O2CMe)(H2O)2](ClO4)2·H2O·MeCN (1) and [Mn(III)Mn(II)L(μ-O2CPh)(MeOH)(ClO4)](ClO4) (2), and a Mn(III)Mn(II)Mn(II)Mn(III) complex, [{Mn(III)Mn(II)L(μ-O2CEt)(EtOH)}2(μ-O2CEt)](ClO4)3 (3), derived from the Robson-type macrocycle H2L, which is the [2 + 2] condensation product of 2,6-diformyl-4-methylphenol and 2,2-dimethyl-1,3-diaminopropane. In 1 and 2 and in two Mn(III)Mn(II) units in 3, the two metal centers are bridged by a bis(μ-phenoxo)-μ-carboxylate moiety. The two Mn(II) centers of the two Mn(III)Mn(II) units in 3 are bridged by a propionate moiety, and therefore this compound is a dimer of two dinuclear units. The coordination geometry of the Mn(III) and Mn(II) centers are Jahn-Teller distorted octahedral and distorted trigonal prism, respectively. Magnetic studies reveal weak ferro- or antiferromagnetic interactions between the Mn(III) and Mn(II) centers in 1 (J = +0.08 cm(-1)), 2 (J = -0.095 cm(-1)), and 3 (J1 = +0.015 cm(-1)). A weak antiferromagnetic interaction (J2 = -0.20 cm(-1)) also exists between the Mn(II) centers in 3. DFT methods properly reproduce the nature of the exchange interactions present in such systems. A magneto-structural correlation based on Mn-O bridging distances has been proposed to explain the different sign of the exchange coupling constants. Utilizing 3,5-di-tert-butyl catechol (3,5-DTBCH2) as the substrate, catecholase activity of all the three complexes has been checked in MeCN and MeOH, revealing that all three are active catalysts with Kcat values lying in the range 7.5-64.7 h(-1). Electrospray ionization mass (ESI-MS positive) spectra of the complexes 1-3 have been recorded in MeCN solutions, and the positive ions have been well characterized. ESI-MS positive spectrum of complex 1 in presence of 3,5-DTBCH2 has also been recorded, and a positive ion, [Mn(III)Mn(II)L(μ-3,5-DTBC(2-))](+), having most probably a bridging catecholate moiety has been identified.

A tale of crystal engineering of metal complexes derived from a special ligand family having a cosmopolitan compartment

The journey of the syntheses and studies of the structures and properties of metal complexes derived from double-compartment 3-ethoxysalicylaldehyde-diamine (H2LOEt) ligands was started in 1995, as per the CSD version 1.15 (2012) record. After dealing with mainly mononuclear complexes in the early years, the “metallo-ligand as reactant” approach was started in 2002 with the reporting of a CuIIGdIII compound, with the aim to explore the magnetic properties of 3d–4f systems. It was realized within a few years that the O(phenoxo)2O(ethoxy)2 compartment has strong potential to interact with water molecule(s) due to the formation of bifurcated hydrogen bonds, resulting in the stabilization of the mononuclear inclusion products and two-component and even three-component cocrystals. “Metallo-ligand as reactant” was reacted with several metal ions from various parts of the periodic table (s, p, 3d, d10, 4f, 5f) as well as with possible hydrogen bond donors, such as an ammonium ion, diprotonated diamines, dicarboxylic acids and aquated proton (perchloric acid). A number of cocrystals, supramolecular dimers, a new type of hydrate isomerism, systems with interesting topologies and systems showing resemblances of entirely different types of metal ions have been obtained. Eventually, we can call the H2LOEt a special ligand family and the O(phenoxo)2O(ethoxy)2 compartment a cosmopolitan compartment. This highlight deals with the metal complexes derived from 3-ethoxysalicylaldehyde-diamine ligands from a crystal engineering perspective.

Crystal structures of discrete, one-dimensional and cocrystalline copper(II)–uranyl(VI) systems: the influence of the reactant ratio in the competition between hydrogen bonds and coordinate bonds

This paper presents the syntheses and crystal structures of four copper(II)–uranyl(VI) compounds [{CuIILOEt–en}2·{(UVIO2)(NO3)2(H2O)2}] (1), [CuII(MeCN)LOEt–pn(UVIO2)(NO3)2] (2), [(UVIO2)2(μ-H2O)2(NO3)4]∙4[CuIILOEt–py(H2O)]∙2MeCN (3) and {[CuIILOMe–en(UVIO2)(NO3)]2[(UVIO2)2(μ-HO)2(NO3)4]}n (4), where H2LOEt–en, H2LOEt–pn, H2LOEt–py and H2LOMe–en are 3-ethoxysalicylaldehyde-diamine (H2LOEt) or 3-methoxysalicylaldehyde-diamine (H2LOMe) ligands in which the diamine functionality are ethylenediamine, 1,3-diaminopropane, 2,3-diaminopyridine and ethylenediamine, respectively. Compound 1 is a [1 × 2 + 1 × 1] trinuclear cocrystal containing two mononuclear [CuIILOEt–en] and one mononuclear [(UVIO2)(NO3)2(H2O)2] moiety; two coordinated water molecules interact with two O4 compartments by forming hydrogen bonds. Compound 2 is a dinuclear system in which two phenoxo oxygen atoms coordinate with the uranium(VI) centre. Compound 3 is a [2 × 1 + 1 × 4] hexanuclear cocrystal of four mononuclear [CuIILOEt–py(H2O)] units and one dinuclear [(UVIO2)2(μ-H2O)2(NO3)4] moiety; O–H⋯O and C–H⋯O interactions interlink the five units here. In 4, there are two dinuclear [CuIILOMe–en(UVIO2)(NO3)]+ cations and one dinuclear [(UVIO2)2(μ-HO)2(NO3)4]2− anion, which are self-assembled to generate a one-dimensional topology. Interesting structural aspects including the weak interaction directed self-assemblies and most importantly, the competition between hydrogen bond and coordinate bond formation and the influence of the reactant ratio in governing that competition are discussed. The diffuse reflectance or solution transmission spectra (for the d–d band) of 1–4 and the corresponding mononuclear copper(II) precursors are also described.

Metal complex analogues of crown ethers as the preorganized motif to stabilize aquated proton in solid state

The work in this report presents the syntheses, characterization and crystal structures of [{CuIILop}2(H5O2)](ClO4) (1), [{CuIILhex}2(H5O2)](ClO4) (2) and [{CuIILen}2(H5O2)](ClO4) (3) derived from three 3-ethoxysalicylaldehyde-diamine Schiff base compartmental ligands H2Lop, H2Lhex and H2Len, in which the diimine moieties come from ortho-phenylenediamine, trans-1,2-diaminocyclohexane and ethylenediamine, respectively. Compounds 1 and 2 crystallize in triclinic crystal system having P space group, while the crystal system and space group of compound 3 is monoclinic P21/c. In the [{CuIILop/hex/en}2(H5O2)]+ cation in 1–3, the two OH2 sites of the aquated proton, H5O2+, interact with two O(phenoxo)2O(ethoxy)2 compartments of the two [CuIILop/hex/en] moieties by forming bifurcated hydrogen bonds and thus [{CuIILop/hex/en}2(H5O2)]+ may be considered as a supramolecular dimer of two mononuclear moieties, self-assembled by H5O2+ as the tecton. On the basis of the extent of the difference in the two O–H distances involving the central hydrogen atom, H5O2+ moieties in 1–3 may be considered as H2O+–H⋯OH2 (in 1) or as the resonance hybrid of H2O+–H⋯OH2 and [H2O⋯H⋯OH2]+ (in 2 and 3). A unique aspect in the composition of 1–3 in terms of the interaction of metal complexes with an aquated proton has been discussed.

Syntheses, crystal structures, magnetic properties and ESI-MS studies of a series of trinuclear CuIIMIICuII compounds (M = Cu, Ni, Co, Fe, Mn, Zn)

Six trinuclear CuIIMIICuII compounds (M = Cu, Ni, Co, Fe, Mn, Zn) derived from the Schiff base ligand, H2L (2 + 1 condensation product of salicylaldehyde and trans-1,2-diaminocyclohexane) are reported in this investigation. The composition of the metal complexes are [{CuIIL(ClO4)}2CuII(H2O)]·2H2O (1), [{CuIIL(ClO4)}{NiII(H2O)2}{CuIIL}]ClO4·CH3COCH3 (2), [{CuIIL(ClO4)}{CoII(CH3COCH3)(H2O)}{CuIIL(CH3COCH3)}]ClO4 (3) and isomorphic [{CuIIL(ClO4)}2MII(CH3OH)2] (4, M = Fe; 5, M = Mn; 6, M = Zn). Two copper(II) ions in 1–6 occupy N2O2 compartments of two L2− ligands, while the second metal ion occupies the O(phenoxo)4 site provided by the two ligands, i.e., the two metal ions in both CuIIMII pairs are diphenoxo-bridged. Positive ESI-MS of 1–6 reveals some interesting features. Variable-temperature and variable-field magnetic studies reveal moderate or weak antiferromagnetic interactions in 1–6 with the following values of magnetic exchange integrals (H = −2JS1S2 type): J1 = −136.50 cm−1 and J = 0.00 for the CuIICuIICuII compound 1; J1 = −22.16 cm−1 and J = −1.97 cm−1 for the CuIINiIICuII compound 2; J1 = −14.78 cm−1 and J = −1.86 cm−1 for the CuIICoIICuII compound 3; J1 = −6.35 cm−1 and J = −1.17 cm−1 for the CuIIFeIICuII compound 4; J1 = −6.02 cm−1 and J = −1.70 cm−1 for the CuIIMnIICuII compound 5; J = −2.25 cm−1 for the CuIIZnIICuII compound 6 (J is between two CuII in the N2O2 compartments; J1 is between CuII and MII through a diphenoxo bridge).