Where are the tpy embraces in [Zn{4'-(EtO)2OPC6H4tpy}2][CF3SO3]2?

The bromo- and phosphonate ester-functionalized complexes [Zn( 1 ) 2 ][CF 3 SO 3 ] 2 and [Zn( 2 ) 2 ][CF 3 SO 3 ] 2 ( 1 = 4'-(4-bromophenyl)-2,2':6',2''-terpyridine, 2 = diethyl (4-([2,2':6',2''-terpyridin]-4'-yl)phenyl)phosphonate) are reported. The complexes have been characterized by electrospray mass spectrometry, IR and absorption spectroscopies and multinuclear NMR spectroscopy. The single crystal structures of [Zn( 1 ) 2 ][CF 3 SO 3 ] 2 . MeCN . 1 / 2 Et 2 O and [Zn( 2 ) 2 ][CF 3 SO 3 ] 2 have been determined and confirm {Zn(tpy) 2 } 2+ cores (tpy = 2,2':6',2''-terpyridine). On going from X = Br to P(O)(OEt) 2 the {Zn(4'-XC 6 H 4 tpy) 2 } 2+ unit exhibits significant 'bowing' of the backbone and this is associated with changes in packing interactions. The [Zn( 1 ) 2 ] 2+ cations engage in head-to-tail 4'-Phtpy...4'-Phtpy embraces with efficient pyridine...phenylene π-stacking interactions. The [Zn( 2 ) 2 ] 2+ cations pack with one of the two ligands involved in pyridine...pyridine π-stacking; steric hindrance between one C 6 H 4 PO(OEt) 2 group and an adjacent pair of π-stacked pyridine rings results in distortion of backbone of the ligand. This report is the first crystallographic determination of a salt of a homoleptic [M{4'-(RO) 2 OPC 6 H 4 tpy} 2 ] n + cation