Photophysics of hexakis(cyano)chromate(3-) and hexakis(cyano)cobaltate(3-) in polyalcohol-water solutions at room temperature

Abstract

Photophysics of Cr(CN)63' and Co(CN)e3" is the recipient of a NATO Travel Grant (No. 789). References and Notes(1) H. L.

Microsecond Photoluminescence and Photoreactivity of a Metal-Centered Excited State in a Hexacarbene–Co(III) Complex

“…The photophysical properties of [Co­(PhB­(MeIm) 3 ) 2 ] + with UV absorption and orange/red emission most closely parallel similar behavior previously established for [Co­(CN) 6 ] 3– (at low temperatures) with the lowest energy excitation located at 396 nm and emission located at 714 nm . The excited-state lifetime of the 3 T 1 state of [Co­(CN) 6 ] 3– was, however, found to be limited to <5 ns in aqueous solution at 22 °C . Furthermore, the excited-state lifetime of neither CT nor MC states in related Fe­(II) complexes usually exceed a few nanoseconds under ambient conditions .…”

“…Earth-abundant transition metal complexes have received increasing attention in recent years as photoactive components in prospective large-scale approaches for solar energy conversion and photocatalysis. − Several first-row transition metals are interesting in this context, but unfortunately many 3d metal complexes suffer from short excited-state lifetimes compared to their 4d and 5d congeners. , This is due to the presence of low-lying metal-centered (MC) states that facilitate fast, radiationless deactivation which limits their use in light-driven applications. − Nevertheless, significant progress has recently been made to extend the excited-state lifetimes of 3d metal complexes, for example, by innovative ligand design to destabilize MC states by imposing a strong ligand field , or by expanding investigations to a range of unconventional excited-state schemes beyond the common triplet metal-to-ligand charge transfer ( 3 MLCT) state in d 6 complexes. , Though MC states are interesting for spin crossover (SCO) and light-induced excited-state spin trapping (LIESST) applications, , in contrast to charge transfer (CT) states they are typically too low in energy to be interesting for photochemical applications or to display visible emission. , As a rare case among the d 6 complexes, very weak emission was reported from the 3 MC state in [Co­(CN) 6 ] 3– , , while such states have only rarely been possible to observe in Ru­(II) and Fe­(II) complexes. , Recently, remarkable photoproperties for Co­(III) complexes were reported by Hannan and Zysman-Coleman and co-workers . Excited states of mixed triplet ligand-to-metal charge transfer/ligand centered ( 3 LMCT/LC) character showed up to 8.7 ns blue emission in solution at room temperature.…”

“…12,13 Though MC states are interesting for spin crossover (SCO) and light-induced excited-state spin trapping (LIESST) applications, 14,15 in contrast to charge transfer (CT) states they are typically too low in energy to be interesting for photochemical applications or to display visible emission. 8,16 As a rare case among the d 6 complexes, very weak emission was reported from the 3 MC state in [Co(CN) 6 ] 3− , 17,18 while such states have only rarely been possible to observe in Ru (II) and Fe(II) complexes. 19,20 Recently, remarkable photoproperties for Co(III) complexes were reported by Hannan and Zysman-Coleman and co-workers.…”

“…36 The excited-state lifetime of the 3 T 1 state of [Co(CN) 6 ] 3− was, however, found to be limited to <5 ns in aqueous solution at 22 °C. 18 Furthermore, the excited-state lifetime of neither CT nor MC states in related Fe(II) complexes usually exceed a few nanoseconds under ambient conditions. 38 It is worth noting that the photophysical behavior of [Co(PhB(MeIm) 3 ) 2 ] + is fundamentally different from the blue-emitting Co complexes recently presented by Zysman-Colman, Hanan, and co-workers as well as from structurally related Fe carbene complexes.…”

Photoakustik-spektroskopische Untersuchungen an Lösungen von Farbstoffen in Polymermatrizen

“…Polyvinylalkohol (PVA) ist eine häufig benutzte Matrix in der optischen Spektroskopie [8][9][10]. In heißem Wasser ist PVA gut löslich.…”