Interaction of photosynthetic pigments with various organic solvents

Umetsu, Mitsuo; Wang, Zheng-Yu; Kobayashi, Masayuki; Nozawa, Tsunenori

doi:10.1016/s0005-2728(98)00170-4

Cited by 75 publications

(117 citation statements)

References 42 publications

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“…One or both Q bands can be weak while the Soret bands are always intense, these patterns arising as a result of strong electron correlation coupling individual transitions together. This critical effect was well known to Craig and Ross as their pioneering calculation of electron correlation ΔE/1000 cm Observed absorption spectroscopic band spectrum [63] (A/n, blue), emission spectrum reflected about the Q y origin [64] (E/n 5 , green), and magnetic circular dichroism spectrum [63] (DA/n, red) of chlorophyll-a in ether at 298 K, shown as a function of the energy difference to the centre of the Q y band. The 1960s 'traditional', 1980s 'modern', and 2010s 'new' assignments of the Q x origin are indicated.…”

Section: From Understanding Benzene In 1946 To Understanding Chlorophmentioning

confidence: 89%

“…Fig. 1 shows the observed [63] low-resolution Q-band absorption spectrum of Chl-a in the red-orange region and features three resolved bands: an intense band at low frequency followed by two progressively weaker bands shifted to higher frequency by 1400 and 2150 cm À1 . Naively, both the Q x and Q y transitions were expected to show origin bands at low energy followed by a much weaker Franck-Condon allowed vibrational sideband in the range of þ700 up to þ1600 cm À1 , while Q y was from all estimates expected to be an order of magnitude more intense than Q x .…”

Section: From Understanding Benzene In 1946 To Understanding Chlorophmentioning

confidence: 99%

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Putting David Craig’s Legacy to Work in Nanotechnology and Biotechnology

Reimers¹

2016

Aust. J. Chem.

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left us with a lasting legacy concerning basic understanding of chemical spectroscopy and bonding. This is expressed in terms of some of the recent achievements of my own research career, with a focus on integration of Craig's theories with those of Noel Hush to solve fundamental problems in photosynthesis, molecular electronics (particularly in regard to the molecules synthesized by Maxwell Crossley), and self-assembled monolayer structure and function. Reviewed in particular is the relation of Craig's legacy to: the 50-year struggle to assign the visible absorption spectrum of arguably the world's most significant chromophore, chlorophyll; general theories for chemical bonding and structure extending Hush's adiabatic theory of electron-transfer processes; inelastic electron-tunnelling spectroscopy (IETS); chemical quantum entanglement and the Penrose-Hameroff model for quantum consciousness; synthetic design strategies for NMR quantum computing; Gibbs free-energy measurements and calculations for formation and polymorphism of organic self-assembled monolayers on graphite surfaces from organic solution; and understanding the basic chemical processes involved in the formation of gold surfaces and nanoparticles protected by sulfur-bound ligands, ligands whose form is that of Au 0 -thiyl rather than its commonly believed Au I -thiolate tautomer.

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Section: From Understanding Benzene In 1946 To Understanding Chlorophmentioning

confidence: 89%

Section: From Understanding Benzene In 1946 To Understanding Chlorophmentioning

confidence: 99%

Putting David Craig’s Legacy to Work in Nanotechnology and Biotechnology

Reimers¹

2016

Aust. J. Chem.

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“…8 is the magnetic-circular-dichroism (MCD) spectrum of chlorophyll-a in ether. [102] This is like the absorption spectrum except that Q x subtracts from Q y instead of adding to it, and the relative intensities are different with the two bands being of roughly equal importance in the MCD but Q x being relatively weak in absorption. The large negative signal at þ2150 cm À1 expected from the traditional assignment is obvious, but a second unexpected negative signal also appears at þ1000 cm À1 .…”

mentioning

confidence: 91%

“…If the normal vibrational modes of the ground and excited-states are the same, then the absorption and reflected emission spectra would precisely overlap, but Duschinsky rotation of the modes occurs and this can have a profound effect on sideband shape and intensity, as evidenced in detail for bacteriochlorophyll-a. [104] The significant enhancement of the absorption intensity at þ2150 cm Observed absorption spectral band spectrum [102] (A(n-n 00 )/n, blue), emission spectrum reflected about the Q y origin [103] (E(n 00 -n)/n 5 , green), and magnetic circular dichroism spectrum [102] (DA(n-n 00 )/n, red) of chlorophyll-a in ether at 298 K, shown as a function of the energy difference to the centre of the Q y band. The 1960s 'traditional', 1980s 'modern', and 2010s 'new' assignments of the Q x origin are indicated.…”

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confidence: 99%

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The Importance of Motions that Accompany Those Occurring Along the Reaction Coordinate

Reimers

2015

Aust. J. Chem.

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The reaction coordinate is a well known quantity used to define the motions critical to chemical reactions, but many other motions always accompany it. These other motions are typically ignored but this is not always possible. Sometimes it is not even clear as to which motions comprise the reaction coordinate: spectral measurements that one may assume are dominated by the reaction coordinate could instead be dominated by the accompanying modes. Examples of different scenarios are considered. The assignment of the visible absorption spectrum of chlorophyll-a was debated for 50 years, with profound consequences for the understanding of how light energy is transported and harvested in natural and artificial solar-energy devices. We recently introduced a new, comprehensive, assignment, the centrepiece of which was determination of the reaction coordinate for an unrecognized photochemical process. The notion that spectroscopy and reactivity are so closely connected comes directly from Hush's adiabatic theory of electron-transfer reactions. Its basic ideas are reviewed, similarities to traditional chemical theories drawn, key analytical results described, and the importance of the accompanying modes stressed. Also highlighted are recent advances that allow this theory to be applied to general transformations including isomerization processes, hybridization, aromaticity, hydrogen bonding, and understanding why the properties of first-row molecules such as NH 3 (bond angle 1088) are so different to those of PH 3 -BiH 3 (bond angles 90-938). Historically, the question of what is the reaction coordinate and what is just an accompanying motion has not commonly been at the forefront of attention. In our new approach in which all chemical processes are described using the same core theory, this question becomes thrust forward as always being the most important qualitative feature to determine. Chemists mostly consider reactions using a single nuclear coordinate, the reaction coordinate.[1] A simple example of this is apparent in the London-Eyring-Polanyi-Sato [2] (LEPS) potentialenergy surface for the chlorine atom-exchange reaction [3] Clthat is shown in Fig. 1a as a function of the bond lengths R ab and R bc . The reaction coordinate indicates the lowest-energy path that connects reactants to products and is shown in blue in the figure. When a reaction occurs, molecular geometries change holistically, and this coordinate in general is therefore complex, embodying what happens to all atoms including atoms in any solvent or surrounding medium. All other motions are thought to smoothly and perhaps even instantaneously adjust to motion along the reaction coordinate. Fig. 1b displays the energy profile [3] for the chlorine atom-exchange reaction as a function of the reaction coordinate, showing how the energy increases from that at the floor of the reactant valley as the approaching atom gets closer to the molecule, going through a maximum at the reaction's transition state (TS). However, Fig. 1c shows how the distance R ac bet...

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Structural and Photophysical Characterization of All Five Constitutional Isomers of the Octaethyl‐β,β′‐dioxo‐bacterio‐ and ‐isobacteriochlorin Series

Brückner

Chaudhri

Nevonen

et al. 2021

Chemistry A European J

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It is well‐known that treatment of β‐octaethylporphyrin with H2O2/conc. H2SO4 converts it to a β‐oxochlorin as well as all five constitutional isomers of the corresponding β,β’‐dioxo‐derivatives: two bacteriochlorin‐type isomers (β‐oxo groups at opposite pyrrolic building blocks) and three isobacteriochlorin‐type isomers (β‐oxo‐groups at adjacent pyrrolic building blocks). By virtue of the presence of the strongly electronically coupled β‐oxo auxochromes, none of the chromophores are archetypical chlorins, bacteriochlorins, or isobacteriochlorins. Here the authors present, inter alia, the single crystal X‐ray structures of all free‐base diketone isomers and a comparative description of their UV‐vis absorption spectra in neutral and acidic solutions, and fluorescence emission and singlet oxygen photosensitization properties, Magnetic Circular Dichroism (MCD) spectra, and singlet excited state lifetimes. DFT computations uncover underlying tautomeric equilibria and electronic interactions controlling their electronic properties, adding to the understanding of porphyrinoids carrying β‐oxo functionalities. This comparative study lays the basis for their further study and utilization.

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Interaction of photosynthetic pigments with various organic solvents

Cited by 75 publications

References 42 publications

Putting David Craig’s Legacy to Work in Nanotechnology and Biotechnology

Putting David Craig’s Legacy to Work in Nanotechnology and Biotechnology

The Importance of Motions that Accompany Those Occurring Along the Reaction Coordinate

Structural and Photophysical Characterization of All Five Constitutional Isomers of the Octaethyl‐β,β′‐dioxo‐bacterio‐ and ‐isobacteriochlorin Series

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