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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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small (<0.15 ppm) to afford a reliable K,{ value.
Crystals of the methanol complex of meyo-octamethyl-calix[4]pyrrole
were grown from a dichloromethane/metha-nol solution of 1. X-ray
crystallographic analysis revealed that the calix[4]pyrrole unit in l-
2(MeOH) assumes a 1,3-altemate conformation in the solid state (Figure
7). Single molecules of the alcohol lie above and below the macrocycle,
each one held in place by hydrogen bonds to two pyrrolic NH groups
[Npyrr-0MeoH = 3.155(4) ]. Further evidence that methanol is bound to 1,
rather than merely occupying space in the lattice, is given by the inward
tilt of the pyrroles in l-2(MeOH). This effect compresses the "cross
ring'" N,-Nlc and NiA-N1B distances by about
0.15 A relative to those in free 1 even though it is not sufficient to
establish a linear alignment of the three hydrogen-bonded atoms (Npyrr-H-
0ML.OH = 152.1(4)).
Complex 1 2(DMF) has also been studied by X-ray crystallography. As
in the methanol complex, individual symmetry-equivalent guests were found
to occupy sites above and below the calix[4]pyrrole receptor. In this
case, however, each amide substrate was found to be hydrogen bonded to
adjacent pyrrolic subunits (Figure 8). As a result, the calix[4Jpynole
adopts a 1,2-alternate conformation (NPy,T-0DMF 2.908(2) and 2.924(2) A)
in this supramolecular adduct. The unsaturated portion of the amide lies
3.363(3) A above the plane of a third pyrrole ring, a finding that led to
the proposal that a n-n stacking interaction helps to stabilize the
overall 1-2(DMF) complex.'6
Crystals of l-DMSO could be prepared by slow cooling of a hot
saturated solution of the macrocycle in DMSO (Figure 9). The crystals
undergo a phase change between 0 and - 30 C (as evidenced by
differential scanning calorimetry (DSC) and X-ray crystallography
data).60 The DSC results are not completely reversible, perhaps due to
solvent loss during the warming cycle of the scans. In any
Figure 7. X-ray crystal structure of meso-octamethylcalix[4]pyrrole-
methanol complex, WMeOH. The calixpyrrole adopts a 1,3-alternate
conformation. Crystal structure originally published in Allen, W. E.;
Gale, P. A.; Brown, . .; Lynch, V. .; Sessler, |. L. j. Am. Chem. Soc.
1996, /18, 12471. Diagram produced using data from the Cambridge
Crystallographic Database.
45 / Calixpyrroles: Novel Anion and Neutral Substrate Receptors
263
Figure 8. X-ray crystal structure of meso-octamethylcalix[4]pyrrole-
dimethylformamide complex, 1-2DMF. The calixpyrrole adopts a 1,2-
alternate conformation. Crystal structure originally published in Allen,
W. E.; Gale, P. A.; Brown, . T; Lynch, V. .; Sessler, |. L. /. Am.
Chem. Soc. 1996, 118, 12471. Diagram produced using data from the
Cambridge Crystallographic Database.
Figure 9. X-ray crystal structure of meso-octamethylcalix[4]pyrrole-
dimethylsulfoxide complex, 1-2DMSO. The calixpyrrole adopts a 1,2-
alternate conformation. Crystal structure originally published in Lynch,
V. .; Gale, P. A.; Sessler, |. L.; Madeiros, D. Acta Crystallogr. Sect.
(submitted for publication).
event, the calixpyrrole skeleton exists in the 1,3-alternate conformation
in both the low-temperature triclinic form and the room-temperature
monoclinic form. The oxygen atom of the coordinated DMSO guest is
hydrogen bonded to a single pyrrole group of the calix|4]pyrrole in both
the low and room temperature structures.

A new caIix|4]pyrrole containing bulky groups in the /He,yo-position,
wt\y<?-octabenzyIcaIix[4]pyrroIe, 6 was pre-
Figure 10. X-ray crystal structure of meso-octabenzylcalix[4]pyrrole-
acetone complex, 1 ^acetone-acetone^t,^. The calixpyrrole adopts a 1,3-
alternate conformation with the acetone hydrogen bonded to one pyrrole-NH
proton. Crystal structure originally published in Allen, W. E.; Gale, P.
A.; Brown, . .; Lynch, V. .; Sessler, |. L. /. Am. Chem. Soc. 1996,
/18, 12471. Diagram produced using data from the Cambridge
Crystallographic Database.
pared by reaction of pyrrole with 1,3-diphenylacetone in the presence of
methanesulfonic acid and subsequent crystallization of the crude reaction
mixture from acetone.^1 The conformation of the macrocycle in 6-
2(acetone)-acetoneiauiC(, is 1,3-alternate [as in l-2(MeOH)], but the two
acetone guests are both located on the same face of the ligand, held in
place by single hydrogen bonds (presumably as a result of favorable
crystal packing interactions) (Figure 10). One of the acetone molecules
is much closer to the macrocycje than the other (Np:>IT-Oacc.u",e
2.972(6) vs 3.359(6)A), reflecting an almost colinear (177(5) )
arrangement of N-H-Oacctonc atoms in the former case. In contrast, the N-
H-O angle formed with the more distant acetone is 159(4) . This structure
demonstrates that the carbonyl portion of acetone can be accessed by the
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