Books
in black and white
Main menu
Home About us Share a book
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

The porphyrin handbook - Kadish K.M.

Kadish K.M. The porphyrin handbook - Academic press, 2000. - 368 p.
Download (direct link): kadishsmishgulilard2000.djvu
Previous << 1 .. 201 202 203 204 205 206 < 207 > 208 209 210 211 212 213 .. 240 >> Next

boronic-acid ester, a negative charge developed at the boron atom, which
weakened the cationic porphyrin-anionic guest complexation.
The chirality of carbohydrates were sensitively detected by
complexation with porphyrin 83 and by observing the induced CD spectra.90
One carbohydrate molecule can bind two boronic-acid-appended porphyrins
83 using four hydroxy groups. The exciton coupling between two porphyrins
in the CD spectra was used to detect the absolute configuration of the
polyols.
F. QUINONE RECOGNITION
Recognition of quinones by porphyrin-based receptors has attracted
interest since porphyrins and quinones form an electron-transfer redox
pair in metabolic processes. Particularly interesting is the binding of
quinone to porphyrin via noncovalent forces to regulate electron-transfer
reactions. Table 5 lists the binding constants of quinones.
Hayashi and Ogoshi reported a hydrogen-bonding-based porphyrin
receptor for quinones.14 In the binding experiments, /7-benzoquinone and
several niethoxy-/?-benzoqui-nones, as models for ubiquinone, were used
as a guest. X-ray diffraction, as well as UV-Vis and 'H NMR studies
indicated that tetrahydroxyporphyrin 84 binds /)~benzoqui-nones in
toluene via hydrogen-bonding interactions. The binding affinity increased
as the number of methoxy groups
304
Ogoshi et al.
Table 5. Binding Free Energy for Quinones by Porphyrin Hosts
Entry Host Guest -Ѱ/]1 Solvent
Temperature (K) Method Reference
1 aaaa-8 2,3,5,6-tetramethoxy-p-benzoquinone 22.6 CHCI,
288 UV-Vis 25
2 aaa(j-8 2,3,5.6-tetramethoxy-p-benzoquinone 14.6 CHCI,
288 UV-Vis 25
3 acraa-8 2,3-dimethoxy-p-benzoquinone 16.3 CHCI,
288 UV-Vis 25
4 txaa(j-8 2,3-dimethoxy-p-benzoquinone 13.0 CHCI.,
288 UV-Vis 25
5 84 p-benzoquinone 13.4 toluene
298 UV-Vis 14
6 84 2-methoxy-p-benzoquinone 16.7 toluene
298 UV-Vis 14
7 84 2,6-dimethoxy-p-benzoquinone 20.5 toluene
298 UV-Vis 14
8 84 2,3-dimethoxy-p-benzoquinone 23.4 toluene
298 UV-Vis 14
9 84 2,3,6-trimethoxy-p-benzoquinone 25.9 toluene
298 UV-Vis 14
10 84 2,3,5,6-tetramethoxy-p-benzoquinone 33.1 toluene
298 UV-Vis 14
11 84 2-methyl-p-benzoquinone 13.0 toluene
298 UV-Vis 14
12 84 2,3-dimethoxy-6-methyl-p-benzoquinone 21.8 toluene
298 UV-Vis 14
13 84 ubiquinone 18.4 toluene
298 UV-Vis 14
14 84 2,3,5,6-tetrafluoro-p-benzoquinone 6.7 toluene
298 UV-Vis 14
15 84 2,3,5,6-tetrachloro-p-benzoquinone 8.8 toluene
298 UV-Vis 14
16 85 p-benzoquinone 11.3 toluene
298 UV-Vis 14
17 85 2-methoxy-p-benzoquinone 14.2 toluene
298 UV-Vis 14
18 85 2,6-dimethoxy-p-benzoquinone 14.6 toluene
298 UV-Vis 14
19 85 2,3-dimethoxy-p-benzoquinone 13.4 toluene
298 UV-Vis 14
20 85 2,3,6-trimethoxy-p-benzoquinone 15.1 toluene
298 UV-Vis 14
21 85 2,3,5.6-tetramethoxy-p-benzoquinone 13.4 toluene
298 UV-Vis 14
22 85 2-methyl-p-benzoquinone 12.6 toluene
298 UV-Vis 14
23 85 2,3-dimethoxy-6-methyl-p-benzoquinone 13.0 toluene
298 UV-Vis 14
24 85 ubiquinone 12.1 toluene
298 UV-Vis 14
25 85 2,3,5,6-tetrafluoro-p-benzoquinone 9.6 toluene
298 UV-Vis 14
26 85 2,3,5,6-tetrachloro-p-benzoquinone 9.6 toluene
298 UV-Vis 14
27 86 2,3,5,6-tetramethoxy-p-benzoquinone 16.7 toluene
298 UV-Vis 102
84
of quinones increased. The largest binding constant of
6.1 x 105M_I was observed for 2,3,5,6-tetramethoxy-/?-benzoquinone. The
driving force for the binding is simultaneous formation of four hydrogen
bonds between the porphyrin hydroxy groups and the carbonyl and methoxy
groups of the quinone.
G. DNA RECOGNITION
Interactions between water-soluble porphyrins and nucleic acids have a
major topic in porphyrin-based host-guest chemistry. The most intensively
Previous << 1 .. 201 202 203 204 205 206 < 207 > 208 209 210 211 212 213 .. 240 >> Next