Infrared measurements on ultraviolet photolysis products at cryogenic temperatures

Combination of ultraviolet (UV) photolysis with infrared (IR) spectroscopy (or UV/IR for abbreviation) is a powerful tool to study various chemical photoreactions, while cryostat and sample-cell windows define the working ranges for both UV and IR beams. Although diamond window has a very wide transmission range from UV to IR, the extreme cost, the absorptions at 1800-2600 cm(-1) and other problems prevent it from being the solution for all cases. In this paper, a gas-exchange cryostat was modified to realize a UV/mid-IR experiment at cryogenic temperatures. Several windows (including diamond) were discussed as options. A di-nitrogen iron complex trans-[Fe(DMeOPrPE)(2)(N-2)H][BPh4] [DMeOPrPE = 1,2-bis(dimethoxypropylphosphino)ethane] was studied as a real photolysis example. Alternatively, a cold-finger cryostat was modified for UV/far-IR compatible experiments. Non-photolysis samples K-5[Mo4O11 (R,S-Hhomocit)(2)]Cl center dot 5H(2)O (H(4)homocit = homocitric acid) and [(n-Bu)(4)N](2)[Fe4S4(PPh)(4)] were studied at cryogenic temperatures. Sample cell windows can also be used as a natural way for choosing photolysis wavelength (in addition to the use of optical filters). (c) 2012 Elsevier B.V. All rights reserved.