Mono-　and　dinuclear　Hg(II)　complexes　of　bis-(N-heterocyclic　carbene)　bridged　with　calixarene　fragments,　[HgL](PF6)(2)　(4a,　4b)　and　[Hg2L2](PF6)(4)　(5a,　5b),　(L　=　bis{3-(N-1-naphthylmethyl-imidazol-2-ylidene)methyl-5-R-2-methoxyphenyl}methane,　a:　R　=　Me,　b:　R　=　t-Bu)　were　both　obtained　by　treatment　of　corresponding　bis-imidazolium　salts　with　mercuric　acetate.　The　structures　of　complexes　4a　and　5a　were　established　by　X-ray　diffraction.　Mononuclear　complex　4a　displays　a　small　rigid　cavity　consisting　of　a　mercury　cation　and　a　bis-NHC　ligand.　Dinuclear　complex　5a　shows　a　28-memebered　metallamacrocycle　formed　by　two　mercury　cations　and　two　bis-NHC　ligands.　Short　mercury-oxygen　contacts　are　found　between　mercury　cations　and　methoxy　groups　of　ligands　in　4a　and　5a.　Cation-pi-arene　interactions　are　present　between　mercury　cations　and　naphthalene　rings　of　ligands.　Additionally,　the　fluorescent　chemosensing　behaviors　of　complex　5a　with　large　cavity　to　diphenylacetylene,　(E)-azobenzene　and　(E)-4,4＇-azobispyridine　were　investigated.　(C)　2013　Elsevier　B.　V.　All　rights　reserved.