Four bis-benzimidazolium salts, 1,4-bis[1′-( N -R-benzimidazoliumyl)methyl]-2,3,5,6-tetramethylbenzene 2X – ( L 1 H 2 ·(PF 6 ) 2 : R = ethyl, X = PF 6 ; L 2 H 2 ·Br 2 : R = picolyl, X = Br; L 3 H 2 ·Br 2 : R = benzyl, X = Br; and L 4 H 2 ·Br 2 : R = allyl, X = Br), and their three N -heterocyclic carbene (NHC) Pd(II) and Ag(I) complexes, L 1 Pd 2 Cl 4 ( 1 ), L 2 Ag 2 Br 2 ( 2 ), and L 4 (AgBr) 2 ( 3 ), as well as one anionic complex L 3 H 2 ·(Ag 4 Br 8 ) 0.5 ( 4 ), have been synthesized and characterized. Complex 1 adopts a funnel-like type of structure, complex 2 adopts a cyclic structure, and complex 3 is an open structure. In the crystal packing of 1 – 4 , one-dimensional polymeric chains and two-dimensional supramolecular layers are formed via intermolecular weak interactions, including hydrogen bonds, π–π interactions, and C–H···π contacts. The catalytic activities of NHC Pd(II) complex 1 in three types of C–C coupling reactions (Suzuki–Miyaura, Heck–Mizoroki, and Sonogashira reactions) were studied. The results show that this catalytic system is efficient for these C–C coupling reactions.

A novel colorimetric chemosensor was prepared, and its recognition performance for Co2+ was investigated by the fluorescence method and color change.

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NHC Ag(i) and Hg(ii) complexes were prepared and characterized, and the catalytic activities of the NHC Pd(ii) complex in the Suzuki–Miyaura reaction were investigated.

Bis-benzimidazolium salt (S)-2,2′-bis[2″-(N-Et-benzimidazoliumyl)ethoxy]-1,1′-binaphthyl hexafluorophosphate [(S)-L1H2]·(PF6)2 and bis-imidazolium salts (S)-2,2′-bis[2″-(N-R-imidazoliumyl)ethoxy]-1,1′-binaphthyl hexafluorophosphate [(S)-L2H2]·(PF6)2 and [(S)-L3H2]·(PF6)2 (R = ethyl or benzyl), as well as their five N-heterocyclic carbene Hg(II) and Ag(I) complexes such as [(S)-L1Hg(HgBr4)] (1), [(S)-L2Hg(HgBr4)] (2), [(S)-L2Hg(HgI4)] (3), {[(S)-L2Ag](PF6)}n (4) and [(S)-L3Ag](PF6) (5) have been prepared and characterized. Each of complexes 1–3 consists of two rings (one 6-membered ring and one 11-membered ring), in which the oxygen atom in the ligand participates in coordination with Hg(II) ion. In complex 4, 1D helical polymeric chain is formed via biscarbene ligand (S)-L2 and Ag(I) ion. A 15-membered macrometallocycle is constructed through a ligand (S)-L3 and a Ag(I) ion in complex 5. Additionally, the selective recognition of H2PO4 − using complex 5 as a receptor was investigated on the basis of fluorescence and UV/vis spectroscopic titrations. The results indicate that complex 5 can distinguish effectively H2PO4 − from other anions.