title: Formation of water-chlorophyll clusters in dilute samples of chlorophyll-a in ether at low temperature.
abstract: Simultaneously measured absorption (ABS) and magnetic circular dichroism (MCD) spectra of the Q-bands of chlorophyll-a (Chl-a) in ether over 150-186 K reveal that the species that forms at low temperature is a chlorophyll hydrate rather than a diether complex. We have recently proposed a new assignment paradigm for the spectra of chlorophillides which, for the first time, quantitatively accounts for a wide range of observed data. Observations performed at low temperature in ether have historically been very important for the interpretation of the spectra of Chl-a. While our assignment for this system initially anticipated only small spectral changes as the temperature is lowered, significant changes are known to occur. Extensive CAM-B3LYP time-dependent density-functional theory (TD-DFT) calculations verify that the observed spectra of the hydrated species conforms to expectations based on our new assignment, as well as supporting the feasibility of the proposed hydration reactions.
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia. Jeffrey.Reimers@sydney.edu.au.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Reimers
authors.forename: Zheng-Li
authors.initials: ZL
authors.lastname: Cai
authors.forename: Rika
authors.initials: R
authors.lastname: Kobayashi
authors.forename: Margus
authors.initials: M
authors.lastname: Rätsep
authors.forename: Arvi
authors.initials: A
authors.lastname: Freiberg
authors.forename: Elmars
authors.initials: E
authors.lastname: Krausz
mesh_terms: D002734:Chlorophyll / Q000737:chemistry*; D000077194:Chlorophyll A; D003080:Cold Temperature; D004987:Ethers / Q000737:chemistry; D008958:Models, Molecular; D014867:Water / Q000737:chemistry*
chemical_list: D004987:Ethers; D014867:Water; D002734:Chlorophyll; D000077194:Chlorophyll A