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The porphyrin handbook - Kadish K.M.

Kadish K.M. The porphyrin handbook - Academic press, 2000. - 368 p.
Download (direct link): kadishsmishgulilard2000.djvu
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E
(mV) vs. Ag/AgCl
Figure 16. Cyclic voltammogram (lOOmVs ]) of 14 recorded in
dichloromethane (0.1 M n-Bu4NPF6 electrolyte).
i_______i_______i_______i_______i______i_______i_______i_______i
1600 1400 1200 1000 800 600 400 200 0

E (mV) vs. Ag/AgCl
Figure 17. Cyclic voltammograms (lOOmVs ]) of 14 recorded in
dichloromethane (0.1 M n-Bu4NPF6 electrolyte) in the presence of 5 molar
equiv Bu4NF (a), 5 molar equiv Bu4NCI (b), and 5 molar equiv Bu4NH2P04
(c).
i_________i__________i_________i__________i_________i__________i
1600 1200 800 400 0 -400 -800

E (mv) vs. Ag/AgCl
Figure 18. Cyclic voltammograms (lOOmVs ]) of 15 recorded in
dichloromethane (0.1 M n-Bu4NPF6 electrolyte) in the presence of 5 molar
equiv Bu4NF (a), 5 molar equiv Bu4NCl (b), and 5 molar equiv Bu4NH2P04
(c).
45/Calixpyrroles: Novel Anion and Neutral Substrate Receptors
269
shift in the Fc~! /Fc couple is also seen when Cl " anions are added to
15. By contrast the Fc/Fc ~ couple is found to be cathodically shifted
upon the addition of H2PO4 (31 mV) and F (63 mV) anions to this latter
system. Thus, w'hile it is clear that significant electrochemical effects
are caused by the addition of certain anions, the types of shifts
observed are such that no clear conclusions in terms of useful anion-
response correlation can be reached presently.
B. CALIXPYRROLE-MODIFIED HPLC MEDIA
One of the simplest kinds of conjugates to conceive is that wherein a
calix|4|pyrrole is appended lo a solid support. Indeed, the production of
new solid supports, useful for the separation of mixtures of, for
example, specific molecules or ions represents an ongoing challenge in
the area of supramolecular chemistry. Early work by Cram68 and Izatt,
Bradshaw and Christensen64 70 demonstrated that solid supports bound to
crown ether groups could affect the separation of positively charged
species. Inspired by this work, investigations ensued as to whether the
anion-binding ability of the calixpyrroles could be utilized in an
analogous way to produce solid supports capable of separating mixtures of
anions.
The mew-functionalized acid 12 and its /?-functionalized analogue 13
were attached to aminopropyl silica gel using an amide-coupling reagent
(BOP). This produced two new silica solid supports, both of which contain
amidocalix[4|-pyrrole recognition groups, gel M (me.w-hook) and gel
(/?-hook) (Scheme 1).
Gel M and gel both proved to be effective HPLC solid supports that
could be used to separate: (1) F , Cl ~ . Br , HSO4 and H2P04 anions
(compare Table 5); (2) phenyl-
Table 5. Elution Times for Various Anions on Columns M and
Elution times (min)
Anion Silica gel Silica gel M
Chloride " 17.9 ( 0.1)'' 15.2 ( 0.1)"
Dthydrogenphosphate " 22.0 (0.1)'' 20.1 (0.1)''
16.2 (0.1)'' 16.2 ( 0.2)''
Fluoride " 16.9 (0.1)'' 16.4 (0.2)''
Plienyiarsenale ' N.D. 4.9 (0.1)
Benzoate' N.D. 6.9 (0.1)
Betizenesulfonate' N.D. 7.0 (0.1)
Phenylphosphale ' N.D. 15.1 (0.1)
Source: Daia from Sessler, J. L.: Gale, P. .; Genge. J. W, Chem.
liur../. 1998. 4, 1095.
" Anions were eluled as I niM CH*C'N solutions of their
tetiabutylammoniuin salts under the following conditions: Mobile phase.
Cl Flow Rate. 0.40 ml/ min.; Detection: Conducth il\: Column Temperature.
25 C. Times given foi individual elulion of tetrabutylammonium anions.
Anions were eluted as I mM aqueous solutions under the following
conditions: Mobile phase 50 mM phosphate buffer. pH = 7.0: Flow rate. 0.3
ml/min.: Column temperature. 25 C. Detection UV -- 254nni.
N.D. - noi determined
arsenate, phenylphosphate and phenylsulfonate (compare Table 5); and (3)
Cbz-proteeted anionic amino acids (serine, glutamine, alanine,
phenylalanine, tryptophan, aspartate and glutamate) (compare Table 6). As
discussed below, these supports also proved particularly useful in
effecting the charge-based separation of nucleotides and
oligonucleotides.
Figure 19 shows the HPLC-based separation of 5'-adenosine
monophosphate (AMP), 5'-adenosine diphosphate (ADP) and 5'-adenosine
triphosphate (ATP) effected using gel M. The elution order differs from
that observed with other neutral solid supports commonly used for anion
separation (such as the modified silica gel used for reversed
Scheme 1. Synthesis of calixpyrrole silica gels M and B.
aminopropyl silica gel BOP PF6 CH2CI2
aminopropyl silica gel BOP PF6 CH2CI2
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