Two bis-benzimidazolium salts 1,4-bis[n′-(N-benzyl-benzimidazolium-N′-yl)alkoxy]-9,10-anthraquinone hexafluorophosphate (L1H2·(PF6)2 and L3H2·(PF6)2) and two bis-imidazolium salts 1,4-bis[n′-(N-benzyl-imidazolium-N′-yl)alkoxy]-9,10-anthraquinone hexafluorophosphate (L2H2·(PF6)2 and L4H2·(PF6)2) (n = 2 or 3), as well as their four macrometallocycle binuclear N-heterocyclic carbene silver(I) complexes [(L1Ag)2](PF6)2 (1), [(L2Ag)2](PF6)2 (2), [(L3Ag)2](PF6)2 (3) and [(L4Ag)2](PF6)2 (4) were prepared and characterized. In complexes 1–4, each macrometallocycle (30-membered macrometallocycle for 1 and 2, 34-membered macrometallocycle for 3 and 4) was formed by two biscarbene ligands (L1–L4 for 1–4) and two silver(I) ions. In the crystal packings of 1–4, 2D supramolecular layers are formed via intermolecular weak interactions including hydrogen bonds and π–π interactions. Additionally, the selective recognition of o-phenylenediamine (OPD) using 4 as a host compound was investigated using fluorescence and UV/vis titrations. The results indicate that 4 can distinguish effectively o-phenylenediamine from other aromatic amines.

•18-Membered NHC silver(I) macrometallocycle 1 is formed via two ligands (L1) and two silver(I) ions.•The recognition ability of 1 to m-dinitrobenzene (DNB) was researched via fluorescence titrations and 1H NMR titrations.•The experimental results show that 1 has special selectivity for m-dinitrobenzene.•When the detection limit is down to 4.6 × 10–8 mol/L, the detection of 1 to m-dinitrobenzene still is sensitive.•The high selectivity and sensitivity for DNB indicate that 1 can discriminate between DNB and other aromatic compounds.The bis-imidazolium salt 1,4-bis[N-(9′-anthracenyl-methyl)imidazoliumyl]butane hexafluorophosphate (L1H2·(PF6)2) and its N-heterocyclic carbene (NHC) silver(I) macrometallocycle [(L1Ag)2](PF6)2 (1) have been prepared and characterized. 18-Membered macrometallocycle of 1 is formed via two ligands (L1) and two silver(I) ions. The selective recognition of m-dinitrobenzene (DNB) using 1 as a host was studied on the basis of fluorescence titrations, 1H NMR titrations, HRMS spectra and IR spectra. The results indicate that 1 can distinguish effectively m-dinitrobenzene with other aromatic compounds.NHC Ag(I) macrometallocycle 1 has been prepared and characterized. The recognition of m-dinitrobenzene (DNB) using 1 as a host was studied.Download high-res image (113KB)Download full-size image

•Two new benzimidazolium salts 1 and 2 with large conjugated system were prepared.•2 was turned out to be a highly selective and sensitive chemosensor for Cu2+.•2 can distinguish Cu2+ with other cations via naked eyes or fluorescence change.Two new benzimidazolium salts with the same cationic moiety and different anionic moieties 2-[2′-(N-benzyl-benzimidazoliumyl)]-1,4-dihydro-naphtho[1,8-ef]-1,4-diazepine bromide (1) and 2-[2′-(N-benzyl-benzimidazoliumyl)]-1,4-dihydro-naphtho[1,8-ef]-1,4-diazepine hexafluorophosphate (2) were prepared and characterized. The structure of 1 was determined by X-ray single crystal diffraction and 1H NMR and 13C NMR spectroscopy. Selective recognition of 2 for cations (Li+, Na+, K+, NH4+, Ag+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Cr3+, Cd2+, Al3+, Pb2+, Hg+ and Hg2+, and use of their nitrate salts) was investigated by fluorescence and UV/vis titrations in C2H5OH/H2O (v:v = 1:1) at 25 °C. The response of 2 to Cu2+ can be observed through both remarkable fluorescence enhancement and color change under sunlight (from yellow to red). The results indicated that 2 can distinguish Cu2+ from other cations via the instrument and naked eyes, and this is greatly convenient in practical operation.Two benzimidazolium salts with 1,4-dihydro-naphtho[1,8-ef]-1,4-diazepine 1 and 2 have been prepared and characterized. The selective recognition of Cu2+ using 2 as a chemosensor was studied.Download high-res image (185KB)Download full-size image

A bis-benzimidazolium salt with oligoether-linker LH2·(PF6)2 and its 13-membered N-heterocyclic carbene silver(I) crown ether 1 have been synthesized and characterized. The coordination geometry of the silver(I) ion of 1 is nearly linear with a C(7)–Ag(1)–C(23) bond angle of 179.6(1)°. In the crystal packing of 1, a 2D supramolecular layer is formed by π–π stacking interactions from benzimidazole rings. In particular, the selective recognition of I− using 1 as a receptor was studied on the basis of fluorescence and UV/vis spectroscopic titrations.

A series of bis-benzimidazolium (or bis-imidazolium) salts, and their eight N-heterocyclic carbene mercury(II) and silver(I) complexes (1–8) have been synthesized and characterized. Complexes 1–4 and 6 contain similar macrometallocycles formed via one bidentate carbene ligand and one metal ion. Their major differences are their anionic units, which are related to the amount of metal sources added. In complex 7, one 30-membered macrometallocycle is generated via two ligands and two silver(I) atoms in dilute solution. For the open structure of complexes 5 and 8, 5 contains an anionic unit [Hg3Cl8]2−, and 8 is formed as a dimer through two [L3Ag2Cl2] monomers. The study of selective recognition of anions on the basis of fluorescence and UV/vis spectroscopic titrations indicates that macrometallocycle 6 is an effective chemosensor for nitrate anion.

A series of functionalized bis-azolium salts, 1,8-bis[2′-(N-R-azoliumyl)ethoxy]-9,10-anthraquinone hexafluorophosphate L1H2·(PF6)2–L4H2·(PF6)2 (R = Et, CH2Ph and CH2Py, azoliumyl = benzimidazoliumyl or imidazoliumyl), as well as their seven N-heterocyclic carbene mercury(II) and silver(I) complexes [(L2HgBr)2](HgBr4) (1), [L2Hg(HgI4)]2 (2), [L1Hg(HgI4)] (3), [L4Hg(HgI4)] (4), [L1Ag](PF6) (5), [L3Ag](PF6) (6) and [L4Ag](PF6) (7) have been prepared and characterized. In complexes 1 or 2, two 16-membered macrometallocycles are connected together via two bridging halide ions (two bridging bromide ions for 1, and two bridging iodide ions for 2). In complexes 3–7, each molecule contains one 16-membered macrometallocycle formed by one biscarbene ligand (L1 for 3 and 5, L3 for 6, L4 for 4 and 7) and one metal ion (Hg(II) for 3 and 4, Ag(I) for 5–7). In the crystal packings of 1–7, 2D supramolecular layers and 3D supramolecular architectures are formed via intermolecular weak interactions (such as the hydrogen bonds, π–π interactions and C–H⋯π contacts). In addition, the fluorescence emission spectra of the complexes and bis-azolium salts were described. The cyclic voltammetry study for silver(I) complexes 5–7 was conducted.

Bis-benzimidazolium salt (S)-2,2′-bis[2′′-(N-picolyl-benzimidazoliumyl)ethoxy]-1,1′-binaphthyl hexafluorophosphate [(S)-LH2]·(PF6)2 and its NHC palladium(II) complex [(S)-LPd](PF6)2 (1) have been prepared and characterized. Complex 1 is formed by one tetradentate mixed ligand (S)-L and one Pd(II) ion, in which one 15-membered ring and two 6-membered rings are present. In this complex, intramolecular π–π interactions between naphthalene rings and benzimidazole rings are observed. Additionally, the catalytic activity of complex 1 in three types of C–C coupling reactions (Suzuki–Miyaura, Heck–Mizoroki and Sonogashira reactions) was investigated. The results show that complex 1 is an effective catalyst in these coupling reactions.

A series of bis-benzimidazolium (or bis-imidazolium) salts, and their seven N-heterocyclic carbene mercury(II) and silver(I) complexes 2–8, as well as one anionic complex 1 have been synthesized and characterized. In complex 1, two benzimidazole rings point in opposite directions, and π–π interactions between these two benzimidazole rings are observed. In complex 2, two 13-membered macrometallocycles are linked together by one bridging chlorine atom, in which each macrometallocycle is formed by one bidentate carbene ligand (L2) and one Hg(II) ion. In complexes 3–6, each molecule contains one 13-membered macrometallocycle formed by one bidentate carbene ligand and one metal ion. In the crystal packings of 1–8, 1D polymeric chains, 2D supramolecular layers and 3D supramolecular frameworks are formed via intermolecular weak interactions, including hydrogen bonds, π–π interactions and C–H⋯π contacts. Particularly, the selective recognition of Ag+ using 4 as a host compound was studied on the basis of fluorescent and UV/vis spectroscopic titrations.

A series of new acyclic tetrazolium salts featuring a central anthracence building block which were 9,10-substituted with (N-R-azoliumCH2CH2)2NCH2– groups were prepared (azolium = benzimidazolium or imidazolium, R = picolyl, ethyl, nbutyl, or benzyl). These tetrazolium salts were metalated with silver(I) leading to four novel NHC tetranuclear complexes 1–4. Molecular structures of 1–4 and one tetraimidazolium salt L1H4·(HgI4)2 were established by 1H NMR, 13C NMR spectroscopy and X-ray crystallography. Silver(I) η3-arene interactions exist in complex 1. Each molecule of complexes 2–4 contains one 42-membered and two 21-membered macrometallocycles. It was interesting to observe intramolecular extended π–π interactions originated from imidazole–anthracene–anthracene–imidazole in complexes 3 and 4. In addition, the fluorescence emission spectra of the complexes and the tetrazolium salts were studied.

Reaction of ligands (L or LA) with metal salts affords six new metal complexes {[Mn(L)3](ClO4)2}n (1), [Cu(L)(SO4)(H2O)]·1.5H2O (2), [Co(L)(LA)(CH3OH)2]·2CH3OH (3), [Co(L)(DMF)(NO3)2]n (4), [Cd(L)(DMF)(NO3)2]n (5) and [Cu(L)(DMF)(NO3)2]n (6) (L = 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene, LA = fumarate). These complexes are structurally characterized by X-ray diffraction analyses. Analyses of crystal structures of complexes 1 and 2 show that 2D layers with metallomacrocycles are formed via ligand L and metal atoms (Mn(II) for 1 and Cu(II) for 2). The 2D layer with metallomacrocycles in complex 3 is formed via ligand L, fumarate groups and Co(II) atoms. 1D polymeric chains in complexes 4–6 are formed via ligand L and metal atoms (Co(II) for 4, Cd(II) for 5 and Cu(II) for 6). In the crystal packing of complexes 1–6, 3D supramolecular frameworks are formed via intermolecular weak interactions, including π–π interactions and C–H⋯π contacts. π–π interactions between benzimidazole rings are compared. The conformations of metal complexes based on dibenzimidazolyl bidentate ligands with flexible or semi-rigid linkers are described and compared. Additionally, the fluorescence emission spectra of ligand L and metal complexes and the magnetic properties of complexes 2–4 are reported.

Seven Cu(II) and Co(II) complexes [Co(L)2(H2O)2]Cl2 (1), [Cu(L)Cl2]2 (2), [Cu(L)(NO3)2]2 (3), [Cu(L)(SO4)]2 (4), [Co(L)(LA)]n (5), [Cu(L)(OAc)2] (6) and [Co(L)Cl2] (7) (L = 1,2-bis(2′-ethoxy)phenyl-bis(benzimidazole), LA = terephthalate) have been prepared by means of self-assembly of Cu(II) or Co(II) salts with bis-benzimidazolyl chelate ligand L and a 1,2-bis(2′-ethoxy)phenyl linker. These complexes are structurally characterized by X-ray diffraction analyses. In complexes 1–4, two 15-membered macrometallocycles of each molecule are linked together via sharing moieties (the sharing moieties: Co(II) atom for 1, two bridging chlorine atoms for 2, two bridging nitrate groups for 3 and two bridging sulfate groups for 4) to afford a dimer, in which each 15-membered macrometallocycle is constructed from one ligand L and one metal atom (Co(II) for 1 and Cu(II) for 2–4). In complex 5, a 1D polymeric chain with 15-membered macrometallocycles is formed via ligand L, terephthalate and a Co(II) atom. In complexes 6 and 7, each molecule contains a 15-membered macrometallocycle formed by one ligand L and one metal atom (Cu(II) for 6 and Co(II) for 7). In the crystal packings of 1–7, 2D supramolecular layers or 3D supramolecular frameworks are formed via intermolecular weak interactions, including hydrogen bonds, π–π interactions and C–H⋯π contacts. The conformations of the metal complexes based on ligand L are described. Additionally, the fluorescence emission spectra of ligand L and the metal complexes 1–7, and the magnetic properties for complexes 1–7 are reported.

Eight metal complexes, {[Co(bibim-4)2(H2O)2](NO3)2}n (1), {[Cu(bibim-4)2(NO3)](NO3)}n (2), [Co(bibim-3)(TP)]n (3), [Zn2(bibim-3)]2(OAc)4] (4), [Co(bibim-2)(NO3)2]n (5), [Zn(bibim-4)(NO3)2]n (6), [Zn(bibim-4)(OAc)2]n (7) and [Cd(bibim-4)(NO3)2(DMF)]n (8) (bibim-2 = 1,2-bis(benzimidazol-l-yl)ethane, bibim-3 = 1,3-bis(benzimidazol-l-yl)propane, bibim-4 = 1,4-bis(benzimidazol-l-yl)butane and TP = terephthalate) have been prepared by means of the self-assembly of Co(II), Cu(II), Zn(II) or Cd(II) salts, dibenzimidazolyl bidentate ligands bearing alkanyl linkers and terephthalic acid. These complexes are structurally characterized by X-ray diffraction analyses. In complexes 1 and 2, 2D network layers with macrometallocycles are formed via metal centers and the ligand bibim-4. A 2D network layer with macrometallocycles in 3 is formed via Co(II) centers, the ligand bibim-3 and terephthalate molecules. In complex 4, a 20-membered macrometallocycle is formed by two bibim-3 ligands and two Zn(II) atoms. In complexes 5–8, 1D polymeric chains are formed via metal centers and the bibim-2 or bibim-4 ligands. In the crystal packings of complexes 1–8, 2D supramolecular layers and 3D supramolecular frameworks are formed via intermolecular weak interactions, including π–π interactions and hydrogen bonds. The different types of π–π interactions from the benzimidazole ring as well as the conformations of the ligands and metal complexes are described. Additionally, the fluorescence emission spectra of the ligands and metal complexes are reported.

The two dibenzimidazolium salts 2,3-bis[(1-nPr-benzimidazoliumyl)methyl]quinoxaline hexafluorophosphate (H2-1a) and 2,3-bis[(1-Pi-benzimidazoliumyl)methyl]quinoxaline hexafluorophosphate (H2-1b) (nPr = n-propyl and Pi = picolyl) and their four NHC metal complexes [Ag2(1a)2](PF6)2 (2a), [Hg(1a)(OAc)(H2O)]2(PF6)2 (2b), [Ag2(1b)2](PF6)2 (2c) and [Ni(1b)](NiCl4) (2d) have been synthesized and characterized. Each cation in 2a,c possesses a boxlike structure with different sizes. In 2b, one 18-membered macrometallacycle is formed by two bidentate NHC ligands and two mercury(II) atoms, in which an inversion center is observed. In 2d, one nickel(II) atom is surrounded by two carbene carbon atoms and two nitrogen atoms from two pyridine rings to adopt a square geometry. The recognition of Cu2+ using 2a,c as chemosensors by charge transfer was investigated on the basis of fluorescence and UV/vis spectroscopic titrations. The results show that complexes 2a,c are effective chemosensors for Cu2+.

The two Cd(II) and Co(II) 2-D frameworks have been prepared by means of self-assemblies of Cd(II) or Co(II) salts and 1-substituted imidazole and terephthalic acid, and structurally characterized by X-ray diffraction analyses. In complex 1 2-D frameworks with rhombic cavity are formed, in which the each top point of rhombus contains one hexa and two heptacoordinated Cd(II). In complex 2 2-D networks with rectangular cavities are formed, and the opposite benzene rings from carboxyls in each rectangular cavity are parallel.The two Cd(II) and Co(II) 2-D frameworks have been prepared by means of self-assemblies of Cd(II) or Co(II) salts and 1-substitutedimidazole and terephthalic acid, and structurally characterized by X-ray diffraction analyses. In complex 1 2-D frameworks with rhombic cavity are formed, in which the each top point of rhombus contains one hexa and two heptacoordinated Cd(II). In complex 2 2-D networks with rectangular cavities are formed, and the opposite benzene rings from carboxyls in each rectangular cavity are parallel.

Eight metal complexes, {[Co(bibim-4)2(H2O)2](NO3)2}n (1), {[Cu(bibim-4)2(NO3)](NO3)}n (2), [Co(bibim-3)(TP)]n (3), [Zn2(bibim-3)]2(OAc)4] (4), [Co(bibim-2)(NO3)2]n (5), [Zn(bibim-4)(NO3)2]n (6), [Zn(bibim-4)(OAc)2]n (7) and [Cd(bibim-4)(NO3)2(DMF)]n (8) (bibim-2 = 1,2-bis(benzimidazol-l-yl)ethane, bibim-3 = 1,3-bis(benzimidazol-l-yl)propane, bibim-4 = 1,4-bis(benzimidazol-l-yl)butane and TP = terephthalate) have been prepared by means of the self-assembly of Co(II), Cu(II), Zn(II) or Cd(II) salts, dibenzimidazolyl bidentate ligands bearing alkanyl linkers and terephthalic acid. These complexes are structurally characterized by X-ray diffraction analyses. In complexes 1 and 2, 2D network layers with macrometallocycles are formed via metal centers and the ligand bibim-4. A 2D network layer with macrometallocycles in 3 is formed via Co(II) centers, the ligand bibim-3 and terephthalate molecules. In complex 4, a 20-membered macrometallocycle is formed by two bibim-3 ligands and two Zn(II) atoms. In complexes 5–8, 1D polymeric chains are formed via metal centers and the bibim-2 or bibim-4 ligands. In the crystal packings of complexes 1–8, 2D supramolecular layers and 3D supramolecular frameworks are formed via intermolecular weak interactions, including π–π interactions and hydrogen bonds. The different types of π–π interactions from the benzimidazole ring as well as the conformations of the ligands and metal complexes are described. Additionally, the fluorescence emission spectra of the ligands and metal complexes are reported.