A new copper(II) fluorescent sensor 5,10,15,20-tetra((p-N,N-bis(2-pyridyl)amino)phenyl)porphyrin zinc (1) has been designed and synthesized by the Ullmann-type condensation of bromoporphyrin zinc with 2,2'-dipyridylamine (dpa) under copper powder as a catalyst as well as with K2CO3 as the base in a DMF solution. It consists of two separately functional moieties: the zinc porphyrin performs as a fluorophore, and the dpa-linked-to-zinc porphyrin acts as a selected binding site for metal ions. It displays a high selectivity and antidisturbance for the Cu2+ ion among the metal ions examined (Na+, Mg2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Ag+, Zn2+, Cd2+, Hg2+, and Fe3+) and exhibits fluorescence quenching upon the binding of the Cu2+ ion with an "on-off"-type fluoroionophoric switching property. The detection limit is found to be 3.3 x 10(-7) M (3s blank) for Cu2+ ion in methanol solution, and its fluorescence can be revived by the addition of EDTA disodium solution. The design strategy and remarkable photophysical properties of sensor 1 help to extend the development of fluorescent sensors for metal ions.
Two new isostructural complexes [M(H2biim)3][M(btc)(Hbiim)].2H2O (M = Co, (1); M = Ni, (2)) (btc = 1,3,5-benzenetricarboxylate; H2biim = 2,2'-biimidazole) have been synthesized and characterized by single-crystal X-ray diffraction. They present a unique structure consisting of two distinct units: the monomeric cations [M(H2biim)3]2+ and the two-dimensional (2D) anionic polymer [M(Hbiim)(btc)]2-. In the anionic moiety, the Hbiim- monoanion is simultaneously coordinated to one metal atom in a bidentate mode and further to another metal atom in a monodentate mode. The imidazolate groups bridge the two adjacent metal ions into a helical chain which is further arranged in left- and right-handed manners. These chains are bridged by btc ligands into a 2D brick wall structure. The most interesting aspect is that the [M(H2biim)3]2+ cations act as pillars and link the anionic layers via robust heteromeric hydrogen-bonded synthons (9) and (7) formed by the uncoordinated oxygen atoms of carboxylate groups and the H2biim ligands, resulting in a microporous metal-organic framework with one-dimensional (1D) channels (ca. 11.85 angstroms x 11.85 angstroms for 1 and 11.43 angstroms x 11.43 angstroms for 2). Magnetic properties of these two complexes have also been studied in the temperature range of 2-300 K, and their magnetic susceptibilities obey the Curie-Weiss law in the temperature range of 20-300 K (for 1) and 2-300 K (for 2), respectively, showing anti-ferromagnetic coupling through imidazolate bridging. Taking into consideration the Heisenberg infinite chain model as well as the possibility of chain-to-chain and chain-to-cation interactions, the anti-ferromagnetic exchange of 2 is analyzed via a correction for the molecular field, giving the values of g(cat) = 2.296, g(Ni) = 2.564, J = -13.30 cm(-1), and zJ' = -0.017 cm(-1). The microporous frameworks are stable at ca. 350 degrees C. They do not collapse after removal of the guest water molecules in the channels, and they adsorb methanol molecules selectively.
Cyclic water hexamers containing 1-D metal--water chains have been observed in the complexes of [M(H(2)biim)(2)(OH(2))(2)](ina)(2) x 4H(2)O [M = Zn (1) and Co (2), H(2)biim = 2,2'-biimidazole, ina = isoniconate]. The water clusters are trapped by the cooperative association of coordination interactions as well as hydrogen bonds.
Three new complexes of [Co(H 2 biim) 2 (1,2-bdc)] (1), [Cd(H 2 biim)(1,3-bdc)] 2 (2), and [Cd 3 (H 2 biim) 2 (1,4bdc) 3 ]‚2H 2 O (3) (bdc ) benzenedicarboxylate, H 2 biim ) 2,2′-biimidazole) have been synthesized and characterized by single-crystal X-ray diffraction. Complex 1 exhibits a 2-D herringbone architecture with mononuclear building blocks assembled via a robust hydrogen-bonded synthon R 2 2 (9). The homo-and heterochiral assemblies were observed in 1 between the H 2 biim ligand and carboxylate group via single and double hydrogen-bonded synthons R 2 2 (9). Complex 2 is a ribbonlike polymer based on a binuclear unit, and the ribbons are alternately decorated by H 2 biim ligands on both sides and further packed through intercalation of the lateral H 2 biim ligands and hydrogen bonds between the H 2 biim and carboxylate oxygen atoms into 2-D networks. These layers extend into a 3-D architecture via π-π stacking interactions. Complex 3 is a 3-D coordination polymer with a R-Po net topology based on linear trinuclear {Cd 3 O 14 N 4 } clusters. The results indicate that isomeric benzenedicarboxylates give structural diversity in the presence of auxiliary ligand H 2 biim, providing a potential tool for crystal engineering.
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