Spontaneous assembly of a polymeric helicate of sodium with LVO(2) units forming the strand: photoinduced transformation into a mixed-valence product.
The anionic cis-dioxovanadium(V) complex species LVO(2)(-) of a tridentate ONS ligand (H(2)L) can bind sodium ion in a bis-monodentate fashion like a bridging carboxylate group. The product [LVO(2)Na(H(2)O)(2)](infinity) (1) is a water soluble polymeric compound in which the complementary units are held together by the simultaneous use of hydrogen bonding and Coulombic interactions. Crystallographic characterization reveals that 1 is a single stranded helicate with LVO(2)(-) units forming the strand which surrounds the labile sodium ions that occupy the positions on the axis. In solution of protic solvents, viz. water and methanol, 1 is quite stable as indicated by electrical conductivity and (1)H NMR measurements. In aprotic solvents, viz. CH(3)CN, DMF, or DMSO, however, the extended hydrogen bonded network in 1 breaks apart and the helical structure collapses when irradiated with visible light. The product is a mixed-oxidation vanadium(IV/V) species obtained by photoinduced reduction as confirmed by EPR, time dependent (1)H NMR, and electronic spectroscopy. Compound 1 is a rare example of a nonnatural helix where hydrogen bonding interactions play a crucial role in stabilizing the single stranded polymeric structure such as that frequently observed in the biological world.
Dutta
Subodh Kanti
SK
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India.
Samanta
Satyabrata
S
Mukhopadhyay
Suman
S
Burckel
Pannee
P
Pinkerton
A Alan
AA
Chaudhury
Muktimoy
M