Unusual Carbonyl···Carbonyl Interaction in Supramolecular Structures of Silver(I) Complexes with 2,6-Pyridinediylbis(4-pyridinyl)methanone

A series of silver(I) complexes of a higher homologue of di-2-pyridyl ketone, 2,6-pyridinediylbis(4-pyridinyl)methanone (abbreviated as L), consisting of {[Ag(L)(BF 4 )]·H 2 O} ∞ ( 1 ), {[Ag(L)(NO 3 )]·H 2 O} ∞ ( 2 ), [Ag 3 (L) 2 (NO 2 ) 3 (H 2 O)] ∞ ( 3 ), [Ag(L)] 2 (PF 6 ) 2 ( 4 ), {[Ag(L)(CO 2 CF 3 )] 2 } ∞ ( 5 ), [Ag(L)] 2 (SO 3 CF 3 ) 2 ( 6 ), and [Ag(L)] 2 (CO 2 CF 2 CF 3 ) 2 ( 7 ), have been synthesized and characterized. Complexes 1 and 2 are isomorphous helical polymers, 3 is a metallacycle featuring a trisilver(I) core, and 4 − 7 are isostructural complexes containing a common dinuclear [Ag 2 (L) 2 ] 2+ metallacyclic skeleton. All complexes except 4 feature a common dominant intermolecular multipolar carbonyl···carbonyl interaction, which along with argentophilic Ag(I)···Ag(I), π···π, hydrogen-bonding, Ag···O═C, O(trifluoroacetate)···C═O as well as unconventional C═O···π and anion-π(pyridyl) interactions assemble the different coordination motifs ( 1 − 3, 5 − 7 ) into higher-dimensional frameworks. Three principal types of carbonyl···carbonyl interaction exhibiting antiparallel, sheared parallel, and perpendicular motifs are observed, and unusual supramolecular associations such as “···[C═O···C═O] n ···” (in 1 − 2 and 6 ) and “···[C═O···C═O···π] n ···” (in 3 ) and “C═O···C═O···C═O” (in 7 ) are the novel structural features established in these complexes. The geometrical parameters and role of such noncovalent interactions in the construction of the present series of supramolecular metal−organic frameworks are discussed.