Syntheses, Structures, And Characterization Of 3-Sulfobenzoate And Metal String Functional Coordination Compounds

This presentation focuses on synthetic routes, structural studies and characterization of various properties of functional complexes. With the fixing attendance of 3-sulfobenzoate monosodium acid [Na(3-Hsb)] as the acidic ligand, various metal ions were used to obtain novel complexes under the competition of neutral nitrogen-containing ligands. We investigated the coordination behavior of 3-sulfobenzoate (3-sb) and various neutral ligands with metals, and obtained a series of functional complexes. We found the diversity in various properties for our new complexes, such as catalysis, magnetism, electrochemistry, fluorescence, and thermal stability due to the difference in their structures. This paper not only explores monomers and dimers, but also extends our study to the trinuclear metal complexes, mainly trinickel metal string complexes. We carried out the much exploration on the influence of different terminal replacements, such as saturated fatty acids and aromatic acids, using X-ray diffraction data to solve their single crystal structures. With the support of the cyclic voltammetry (CV), we obtained the redox half-wave potential (E1/2) and the highest occupied orbital energy (HOMO), in combination with the band gap derived from UV to calculate the lowest unoccupied orbital energy (LUMO). Thus it is possible to forecast the conductivity of trinuclear nickel-metal complexes. On the other hand, we used SQUID system to determine the electronic states and magnetic properties of the trinickel string complexes.For the copper complexes, we mainly explored how the different reaction conditions, such as the ratio of reactants, temperature, reaction pressure, solvent, synthetic methods and the type of neutral ligands, impact the networks of compounds. We successfully synthesized four CuⅡ/3-sb/2,2'-bipy complexes, [Cu(2,2'-bipy)2(3-sb)]-4H2O (1),{[Cu(2,2'-bipy)(3-sb)(H2O)2]·2.5H2O}n (2), {[Cu(2,2'-bipy)(3-sb)(H2O)]·2H2O}n (3), and{[Cu(2,2'-bipy)(3-sb)(H2O)](H2O)}n (4), and discussed the roles of synthesis methods, various secondary interactions and stacking interactions. Furthermore, we obtained other three CuⅡcomplexes, {[Cu(4,4'-bipy)(H2O)4][Cu(3-sb)2(4,4'-bipy)]·2H2O}n (5) {[Cu(3-sb)(bpe)1.5(H2O)]·3H2O}n (6), and{[Cu(3-sb)(Hdpa)]}n (7), and discussed the contributions of the different scale of the neutral ligands and aromatic stacking interactions.For cadmium(II) complexes, we studied the coordination modes of the neutral heterocyclic ligand and 3-sb, as well as their properties. The results have shown that complex 8,{[Cd2(OAc)2(3-sb)(bpe)2.5(H2O)]·4H2O}n, possesses a 3D interpenetrating network, and it can photocyclodimerize under the irradiation of the sunlight or strong UV, producing 9,{[Cd2(OAc)2(3-sb)(bpe)o.5(4,4'-tpcb)2(H20)]·4H20}n. Moreover, it is an injection of fresh blood for the photodimerization, which is previously only limited to Zn, Ag and Mn. Complexes 10-14,{[Cd(2,2'-bipy) (3-sb)(H2O)2]·H2O}n(10), {[Cd(3-sb)(CH3COO)(4,4'-bipy)][Cd0.5(4,4'-bipy)(H20)2]·3H20}n (11), {[Cd(2)2'-bipy)(bpe)0.5(3-sb)]·2H20}n (12),{[Cd(phen)(bpe)0.5(3-sb)]·2H20}n (13), and [Cd(phen)(4,4'-bipy)0.5(3-sb)(H20)] (14), show the colorful coordination modes and network buildings constructing from CdⅡand 3-sb (1D chains for 10-13 and monomer for 14; six-coordinated octahedral geometry of CdⅡions for all except seven-coordinated in 11), and a large number of hydrogen bonds maintain the stability of the networks. In addition, the coordination of neutral ligands can help to enhance the fluorescence intensity, and the more neutral ligands, the stronger enhancement.For MnⅡ/3-sb/N-heterocyclic ligand system, we synthesized six complexes. Complex 15 or 16, [Mn(4,4'-bipy)2(H2O)4](3-sb)·3H2O (15) and {[Mn(3-sb)(bpe)1.5(H2O)2] (bpe)o.5·H20}n (16), contains one neutral ligand. Each of other complexes, [Mn(3-sb)(phen)(H2O)3](4,4'-bipy)·H2O (17), [Mn2(3-sb)2(phen)2 (4,4'-bipy)(H2O)4] (18), [Mn(3-sb)(phen)2(H20)](bpe)o.5·4H2O (19) and [Mn(3-sb)(phen)2(H20)](bpe)o.5-H2O (20), contains two neutral ligands in which one is phen. The different ratio of two neutral ligands in complexes 17-20 regulates the coordination modes of bpe or 4,4'-bipy:free bpe molecule in 19 and 20, and bridging or free for 4,4'-bipy in 17 and 18, respectively. On the other hand, hydrogen bonding formation capacity andπ-πstacking interactions were affected by the phen in a great extent, resulting in the diverse properties of thermal stability, fluorescence, UV absorption, catalytic decomposition rate, and activity of hydrogen peroxide (H2O2). For NiⅡ/3-sb/N-donor ligands family, we determined five distinct structures, {[Ni(3-sb)(phen)(H2O)2]·H2O}n (21), [Ni(3-sb)(phen)2(H2O)]·H2O (22), [Ni(phen)3]·2(3-Hsb)·10H2O (23),{[Ni(3-sb)(2,2'-bipy)(H2O)2]·H2O}n (24), and [Ni(2,2'-bipy)3]2·(3-Hsb)·3(NO3)·9H2O (25). The molecular structures of these complexes are 1D chains for 21 and 24, monomer for 22, and cation-anion species for 23 and 25. Among them, the existence of the 3-sb exhibits two types:full deprotonation (3-sb2-) participating in coordinating and partial deprotonation (3-Hsb-) existing as a free charge counter. A variety of hydrogen bonds extend 21 and 24 into 2D networks,22 into 1D chain and 23 and 25 into novel 3D host-guest supramolecular networks in which cation ions occupy the holes formed by anionic layers. In addition, these five complexes can be used as catalysts for the oxidation of methyl benzyl sulfide, and 23 exhibits a high catalytic activity, resulting from a crucial role ofπ-πstacking and structural topologies.For ZnⅡ/3-sb/N-donor ligand system, we synthesized two sets of complexes. Each of complexes 26-30, [Zn(2,2'-bipy)3]2(3-sb)(NO3)(HCOO)·10H2O (26), [Zn (4,4'-bipy)2(H2O)4](3-sb)·3H2O (27), [Zn (phen)(3-sb)(H2O)3]·5H2O (28),{[Zn (bpe) (3-sb)2](Hbpe)2(bpe)·3H2O}n (29), and{[Zn (bpe)1.5(3-sb)(H2O)](bpe)0.5·3H2O}n (30), contains one kind of neutral ligand. The geometries of coordination spheres of ZnⅡin complexes 26-30 are diverse (six-coordinated in octahedral configurations for 26,27 and 30, seven-coordinated in pentagonal bipyramidal configuration for 28, and four-coordinated in tetrahedral configuration for 29). These discrepancies were mainly due to variable neutral ligands and interactions with metal centers. Although competitive effects of two neutral ligands in complexes 31-35, {[Zn(2,2'-bipy)(bpe)0.5(3-sb)]·2H2O}n (31),{[Zn(phen)(bpe)0.5(3-sb)]·2H2O}n (32), [Zn(2,2'-bipy)(4,4'-bipy)0.5(3-sb)(H2O)]·(4,4'bipy)·H2O (33), [Zn(phen)(4,4'-bipy)0.5(3-sb)(H2O)] (34), and [Zn(bpe)(4,4'-bipy)0.5(3-sb)(H2O)3]·3H2O (35), led ZnⅡto adopt six-coordinated in an octahedral configuration, the thermal stability of desolvated 31-35 was higher than those of desolvated 26-30.31-35 possess stronger fluorescence intensity than those of 26-30, indicating that in ZnⅡ/3-sb/N-donor ligand system the neutral ligands not only change metal coordination spheres, but also influence their properties.For trinickel metal string complexes, we obtained four complexes with saturated fatty acids as axial ligands, [Ni3(dpa)4(HCOO)2] (39), [Ni3(dpa)4(CH3COO)2]·CH2Cl2H2O (40), [Ni3(dpa)4(CF3COO)2]·2H2O (41), and [Ni3(dpa)4(CH3CH2COO)2][Ni3(dpa)4(CH3CH2COO)(H2O)]·H2O·(ClO4) (42). The emission peaks for 39-42 are completely from Hdpa, and the electron-withdrawing groups greatly reduce the fluorescence emission intensity. Therefore, the order of the fluorescence intensity is presented as 41<39<40<42. The electron effects of the electron withdrawing groups also can be observed in UV spectra. Complex 41 containing the strongest electron withdrawing group shows the strongest absorption. In addition, with the growth of chains, band gap narrowed gradually, and it would certainly also affect the HOMO and LUMO energy levels.We synthesized other six trinickel complexes with aromatic acids as axial ligands, [Ni3(dpa)4(ba)2](43), [Ni3(dpa)4(2-mba)2](44), [Ni3(dpa)4(3-mba)2] (45), [Ni3(dpa)4(4-mba)2] (46), [Ni3(dpa)4(3-hba)2] (47), and [Ni3(dpa)4(4-hba)2](48) where ba is benzoate, mba is methylbenzoate, and hba is hydroxylbenzoate. Their electrochemical and fluorescent properties give a regular change. It is interesting that the fluorescent intensities of complexes with substitute benzoates are not as strong as that of 43, indicating that substituent groups, to some extent, hinder the transfer of electrons between metal and ligands. It is worth noticing that electrochemical behaviors of these complexes were of great interest. E1/2 values of 47 and 48 shift towards anode compared to that of 43 under the introduction of the electron-withdrawing group -OH into the ligands such as methyl, while E1/2 values of 45 and 46 shift towards cathode. Furthermore, the band gaps of 43-48 are larger than those of 39-42, indicating the introducing of the benzene ring is not in favor of the conductivity of trinickel complexes.