Quinoline　bridged　imidazolium　precursors　5,8-bis(N-R-　imidazolylidenylmethylene)quinoline　PF6-　salts　[H　2L](PF6)2　[R　=　Me　(1a),　R　=　naphthylmethyl　(1b)]　were　prepared　by　quaternization　of　N-methylimidazole　and　N-naphthylmethylimidazole　with　5,8-bis(bromomethyl)quinoline,　respectively.　Reaction　of　the　imidazolium　ligands　1a　and　1b　with　Hg(OAc)2　and　Ag2O　in　acetonitrile　gave　the　macrocyclic　transition　metal　carbene　complexes　[Hg2L2](PF6)4　(2a　and　2b)　and　[Ag2L2](PF6)2　(3a　and　3b),　respectively.　All　the　N-heterocyclic　carbene　complexes　were　characterized　in　detail　by　NMR,　ESI-MS,　and　elemental　analysis.　Structures　of　complexes　2a　and　3a　were　determined　by　X-ray　diffraction　studies.　Structural　studies　revealed　that　the　coordination　arrangement　of　the　central　mercury　atom　in　complex　2a　displays　a　tricoordinate　mode　and　the　molecular　conformation　results　in　a＂closed＂　form　with　the　bridging　quinoline　functionality　in　the　macrocycle,　whereas　the　silver　complex　3a　does　not　show　an　coordiantion　between　the　bridging　quinoline　and　the　AgI　ion,　which　results　in　an　＂open＂　conformation　of　the　macrocycle.　The　HgII　and　Ag　I　NHC　complexes　showed　similar　UV　absorption　and　luminescence　in　acetonitrile　solutions.　Copyright　©　2013　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim.