Ag(I)···π-Influenced, Anion-Controlled Structural Variation in Coordination Networks of <i>E</i>-3-Pyridylvinyl Benzoxazole: Sunlight-Driven Regioselective Photodimerization in the Solid State
Shyamvarnan Baskar, Goutam Kumar Kole
Abstract
The coordination chemistry of the flexible N -donor ligand E -3-pyridylvinyl benzoxazole ( 3-PVBO ) with various silver salts has been investigated for the first time. Four novel coordination compounds of silver(I), namely, {[Ag 2 ( 3-PVBO )](BF 4 )} ( 1 ), {[Ag( 3-PVBO )](CF 3 SO 3 )} ∞ 1 ( 2 ), {[Ag( 3-PVBO )(CF 3 CO 2 )]} ∞ 1 ( 3 ), and {[Ag 2 ( 3-PVBO )](SbF 6 )} ∞ 1 ( 4 ), have been synthesized and structurally characterized. 3-PVBO adopts two different configurations, i.e., syn - and anti-, and offers structural variation in the series with different anions. In both 1 and 2, it adopts syn- configuration, and thus, 16-membered metallacycles are formed. In 3, with the trifluoroacetate anion, it adopts anti -configuration, and thus, a zigzag 1D coordination polymeric network is formed. However, in 4 with the SbF 6 – anion, despite it adopting the syn- configuration, instead of a metallacycle, a 1D coordination polymeric network is observed. More interestingly, 3-PVBO ligands were found to stack parallel in 3 and 4, suitable for the photodimerization reaction in the solid state. 3 exhibited photodimerization in the head-to-tail fashion, leading to the formation of the coordination polymer, {[Ag( rctt -HT- PBOCB )(CF 3 CO 2 )]} ∞ 2 ( 5 ), where PBOCB = 1,3-bis(benzoxazole)-2,4-bis(3′-pyridyl) cyclobutane. However, 4 underwent photodimerization in the head-to-head fashion. Thus, varying the anions achieved a regioselective synthesis of functional cyclobutane derivatives. No argentophilic but Ag(I)···π interaction was observed in this series.