Mercury(II), silver(I) and gold(I) thioether crown chemistry: synthesis, electrochemistry and structures of [(HgBr2)2([24]aneS8)], [{Ag2([24]aneS8)(CF3SO3)2(MeCN)2}∞], [Ag2([28]aneS8)][NO3]2 and [Au2([28]aneS8)][PF6]2 ([24]aneS8 = 1,4,7,10,13,16,19,22-...