6918 from the Robert A. Welch Foundation. T h e Syntex P21 diffractometer was purchased with funds provided by the National Science Foundation. Supplementary Material Available: Listing of observed and calculated structure factors (8 pages). Ordering information is given on any current masthead page.
References and Notes (1) University of Houston.
(2) University of Texas at Austin. (3) Southwestern University. (4) A. J. Barkovich and K. P. C. Voilhardt, J. Am. Chem. Soc., 98, 2667 (1976). (5) G. Camaggi, J. Chem. Soc. C, 2382 (1971). (6) R. L. Soulen, S . K. Choi, and J. D. Park, J. Fluorine Chem., 3, 141 (1973174).
(7) G. Germain, P. Main, and M. M. Wooifson, Acta Crystallogr.,Sec. A, 27, 368 (1971). (8) D. T. Cromer and J. B. Mann, Acta Crystallogr., Sect. A, 24, 321 (1968). (9) W. H. Milis and iI G. Nixon, J. Chem. SOC., 2510 (1930). (10) (a)R. A. Finnegan, J. Org. Chem., 30,1333(1965):(b) A. Streitweiser,Jr., G. R. Ziegler, P. C. Mowry, A. Lewis, and R. G. Lawler, J. Am. Chem. SOC., 90,1357 (1968). (1 1) We have recently examined in detail the structure of dicyclopentenobenzocyciobutene. Although this molecule shows good evidence for rehybridization of its aromatic carbons, w e again observe no bond alternation in the benzene ring: J. D. Korp, R. P. Thummei, and I. Bernal, Tetrahedron,
in press.
Sheppard and C. M. Sharts, "Organic Fluorine Chemistry", W. A. Benjamin, New York, N.Y., 1969. (13) C. J. Marsden, J. Mol. Struct., 21, 168 (1974). (14) F. W. B.Einstein and A. C. MacGregor, J. Chem. SOC.,Dalton Trans., 783 (1974). (15) H. P. Lemaire and R . L. Livingston, J. Am. Chem. Soc., 18, 569 (1950). (12) W. A.
Crystal and Molecular Structure of 2,3-Dihydroa,@, y ,a-tetraphen ylporphyrinatopyridinezinc( 11)Benzene Solvate' L. D. Spaulding,*2a L. C. Andrews,2band Graheme J. B. Williams2b Contribution from the Departments of Applied Science and Chemistry, Brookhaven National Laboratory, Upton, New York 1 1 973. Received April 30, 1977
Abstract: The structure of 2,3-dihydro-a,R,y,b-tetraphenylporphyrinatopyridinezinc( 11)-benzene solvate, ZnTPC(Py).C,jH,j, has been determined from three-dimensional x-ray diffraction. The compound crystallizes with one molecule of benzene and one ZnTPC(Py) per asymmetric unit in the triclinic space group PI with a = 11.414 (2) A, b = 13.334 (2) A, c = 14.809 (1) A, a = 99.18 (l)', /3 = 94.14 (l)', and y = 105.08 (1)'. The structure has been refined by block-diagonal least-squares to R = 0.046 based on 8792 measured intensities with a 13:l parameter-to-variable ratio. Agreement of chemically similar bond distances and angles is excellent. The reduced pyrrole ring is clearly distinct with a Cp-Cp distance of 1.478 (3) A and C,-Co distance of 1.495 (2) A. Comparison of ZnTPC(Py) with analogous porphyrins shows the effect of reduction on the porphyrin macrocycle and on the zinc coordination. Differences in the orientations of the reduced pyrrole ring hydrogen atoms in chlorophylls and ZnTPC(Py), previously predicted by ESR experiments, are confirmed.
Metallotetraphenylporphyrins, M T P P , Figure l a , have been widely studied by x-ray diffraction as models of naturally occurring porphyrin^.^ T h e dihydrotetraphenylporphyrins (tetraphenylchlorins), Figure 1b, have been used to model no structure of a metallotetraphenyl~ h l o r o p h y l l however, ;~ chlorin has been determined to date. Such a structure would illustrate the effect of reducing the porphyrin conjugated x-electron system, and allow direct comparison with the recently determined structures of ethylchlorophyllides as and b.6 W e present here the structural determination of 2,3-dihydrotetraphenylporphyrinatopyridinezinc(11)-benzene solvate.
Experimentat Section Tetraphenylchlorin (TPCH2) was prepared by standard methods' and reacted with zinc acetate in pyridine to form 2,3-dihydroa,P,y,b-tetraphenylporphyrinatopyridinezinc(11), ZnTPC(Py) .s The reaction mixture was partitioned between benzene and water, and the organic layer washed with water. The product was crystallized from benzene and dried in vacuum at room temperature. A combination of diffusion and evaporation at room temperature using Fisher Certified hexanes and dichloromethane, distilled from calcium hydride, as solvents yielded crystals suitable for diffraction studies. A purple prism (0.3 X 0.7 X 0.4 mm) was mounted along its long axis and the crystallographic properties were examined on a precession camera. Good quality diffraction patterns, exhibiting only inversion symmetry, were obtained. After approximate cell dimensions were measured, the crystal was mounted on an Enraf-Nonius CAD4 diffractometer. Some crystallographic details are given in Table I. During the 2 weeks of data collection, three reflections were mon-
Journal of the American Chemical Society
itored periodically. The intensities of these reflections showed no significant trends or fluctuations; therefore no time-dependent correction for experimental instability was made. Solution and Refinement. The position of the zinc atom was determined from a vector map, and electron-density and difference-electron-density syntheses were used to obtain positions for all other nonhydrogen atoms. This model was refined by block-diagonal least-squares against the 7760 data with IF,) > 12uJF,).A further difference map indicated positions for all hydrogen atoms except those of the benzene molecule of solvation. Refinement was continued against all the unique intensity data ( I s ) , except 3.4.4 which was omitted because of an unusually large weighted discrepancy. All nonhydrogen atoms were permitted anisotropic expression of their thermal motion, but each hydrogen atom was restricted to a single isotropic vibration parameter. Hydrogen atoms of the benzene solvate were placed in their calculated positions and periodically updated. Because of the apparently very high thermal motion of the benzene ring, refinement of the occupancy factors for its atoms was attempted. Values near unity resulted, and so full occupancy was assumed. Refinement was terminated when the parameter shifts for all nonhydrogen atoms, except those for the benzene solvate, were reduced to less than their nominal standard deviations. The largest positional shift in the final cycle was 1.08 u for two hydrogen atoms, and the largest change in a vibrational parameter was 1.9 u for L / 2 3 of C(55). A final difference synthesis revealed a peakof height -0.6 e/A3 near the benzene ring as its most prominent feature. The region near the reduced pyrrole ring was carefully examined for evidence of conformational or rotational disorder, but no evidence for these phenomena was found. Final residuals are given in Table I. The structure and numbering system are shown in Figure 2 and the atomic positions are given in Tables I1 and 111. The bond distances
1 99:21 1 October 12, 1977
6919 Table I. Crystallographic Details Unit cell: space group, triclinic, pi V = 2133 A’ a = 11.414 (2) 8,. a = 99.18(1)’ b = 13.334(1)8, = 94.14(2)’ c = 14.809 ( I ) 8, y = 105.08 ( I ) ’ z=2 Density Obsd (aqueous K I ) , 1.23 g/cni3 Calcd for 2 X [(CssH;6NsZn)/cell], 1.25 g/cm3 Crystal description: triclinic prism, ( I O O ) , lolo), { O O l ~ [ O 11 I d (100, 100) = 0.15 mm d (001,OOl)= 0.19 mm d (010,010) = 0.37 mm d (01 I , 01 1) = 0.34 m m Val = 0.085 mm3 Data collection Diffractometer, Enraf-Nonius, CAD4 Radiation, Cu Ka-graphite monochromated, X = 1.54051 A Attenuator, nickel foil, l o / l ~ , = , 15.55 Linear absorption coefficient, 12.28 cm-’ (Cu KCY) Two 0 range, 0 C 28 C 140°] No. of reflections. 1 1 563 measured h > 0, 8792 unique Scattering factors, Cromer and Mann9 Anomalous dispersion, Cromer and Liberman’O Refinement: block-diagonal least-squares against I s R , = 0.06 RF.= 0.03 ( I F 1 > 0) R,, = 0.1 I R,F = 0.06 (IF1 > 0 )
MTPP IA
Programs used Absorption correction and averaging B h L A B S / A V S O R T 2 3 Thermal motion analysis TLS6 (Schomaker and T r ~ e b l o o d ) ~ ~ . ’ ~ Figure 5 ( P R J C T N ) (McCandlish, Andrews, Bernstein. 1 975)” All others X R A Y 7 6 (Stewart et ( I Here and subsequently the standard deviations of the least significant figure are given in parentheses.
MTPC 1B
Figure 1. Structural formulas and atom designation for a metallotetra-
phcnblporphyrin ( l a ) and a metallotetraphenylchlorin ( l b ) .
and angles are embodied in Tables I V , V , and V I . Throughout this analysis there was no indication that the structure had symmetry lower than t h a t of space group PI. A tabulation of the observed and calculated amplitudes is available.”
Results and Discussion In structures with a high degree of internal redundancy, the agreement between chemically similar bond lengths can be used to indicate the reliability of the analysis, and also to provide an indication of the true standard deviations in these quantities. Table IV indicates that for this analysis the agreement is, in general, very good, although the least-squares estimates of the standard deviations appears to be too low by a factor of -2.5. The reduced pyrrole, ring I , is clearly distinct from the other three as indicated by the bond distance involving the saturated carbon atoms C(2) and C(3). T h e C,-Cpdistances of the reduced ring (average 1.495 (2) A) a r e longer than those of the other three pyrroles by an average of 0.052 A. The C&o bond of the saturated pyrrole in this structure (1.478 (3) A) is markedly longer than the other three Cp-C@bonds (average 1.363 (4) A). I t is, however, significantly shorter than the comparable linkage observed in the other crystallographic studies of chlorin compounds. In the ethylchlorophyllides a and b, 1.56 Ass6 was found and, for ethylpheophorbide,I* the analysis yielded 1.55 A. T h e difference between these latter values and that found here seemed abnormally large, and perhaps indicative of some unrecognized error. A careful examination of the difference-electron-density m a p as noted above and an inspection of the apparent thermal motion of the atoms in this region revealed no evidence of experimental or procedural error. Therefore, we conclude that for the case of only hydrogen atoms as exocyclic substituents of the Cp atoms, the Co-Cp bond has the expectation value we report here. The chlorophyllide and pheophorbide structures alluded to bear
Spaulding, Andrews, Williams
alkyl substituents exocyclic to the saturated ring, and the Cp atoms of these rings are displaced above and below the ring planes by 0.076 A on average. I n ZnTPC(Py) these deviations average 0.01 7 A. The Cp-Cp distance given here falls in the range 1.42 to 1.54 8, found in simple pyrrolidine derivatives. 13x14 The reduction of a double bond in the porphyrin macrocycle to form a chlorin has very little effect on the geometry of the macrocycle. The average bond lengths within the porphyrin ring for a,~,y,6-tetra-4-pyridylporphyrinatopyridinezinc(ll), ZnTPyP(Py),Is are given in Table IV along with the values for the phenyl rings from SnTPP(Cl2).l6 These values agree to within one standard deviation as d o the corresponding bond angles given in Table V I . There appears to have been no change in size of the central hole of this molecule upon reduction. From the center, C t , of the macrocycle, determined from the average of N ( I ) , N(2), N(3), and N ( 4 ) coordinates, the average C , - C M ~ distance is 3.445 8, and the average C,-C, distances is 3.070 A. The corresponding values in ZnTPyP(Py) a r e 3.477 A and 3.061 A.15
The coordination geometry of the Zn(l1) ion is that of a distorted square pyramid, Figure 3. The metal ion forms bonds 2.061 ( I ) , 2.072 ( I ) , and 2.063 ( I ) 8, in length to the nitrogen atoms of rings 2 , 3 , and 4 and is 2.130( 1) 8, from the reduced pyrrole ring. This pattern of metal-macrocycle bond lengths was also observed in the ethylchlorophyllide structures. These observations support the x-ray photoelectron spectroscopy studiesr7and molecular orbital calculations1*on M T P C which indicate that N ( 1 ) is electron deficient relative to the other pyrrole nitrogen atoms and may be expected to bond less strongly to a metal ion. Because of this decreased electron donation from the equatorial ligands in Z n T P C over that in Z n T P P it is expected that the former compound is a stronger
/ 2,3-Dihydro-~u,~,y,G-tetraphenylporphyrinatopyridinezinc~ll~-Benzene
6920 Table 11. Atomic Coordinates and Anisotrouic Thermal Vibration Coefficients for the Nonhydroeen Atoms X
Y
43 1 38 . 9 I1 . 7 1 16315.6(1.5) 43990( 12) 614C 18) 34543( 121 16004(9) 47333( 12) 32661(18) 56421 (121 17427( 18) 26676( 13) 1 155 1 ( 1 1 1 39812(141 -5024( 12) 47488( 18) - 16 127 ( 14) 38736( 18) -16825C14) 3723 1 ( 14) -5938( 12) 23567(13) -$166(11) '>8474(14) 1057(12) 20815( 17) 9624( 14) 22756( 16) 20370 ( 14) 3122 1 ( 14) 24339( 12) 34837 ( 14) 34846( 12) 42541 ( 15) 38692( 12) 47028 ( 17) 49689( 13) 54779( 18) 58167( 13) 54903( 15) 39557(12) 6 195 1 ( 14) 367 13 ( 12) 62608 ( 14) 26487(12) 78488( 17) 23812(14) 13239( 14) 68883(17) 60212(14) 9334( 12) 5695OC 14) -1245(12) 21447( 14) -11973(12) 25488( 16) -15768( 14) 17676( 19) -24824( 15) 6875( 17) -28583 ( 14) -24828( 16) 1942( 16) - 1655 1 ( 15 1 9515(16) 30318(14) 42633( 12) 33812f18) 449 1 2 ( 16) 23363,221 51959(17) 2 1235 ( 2 1 1 56745 ( 16) 177 18 ( 2 1 ) 54633 ( 16) 47693 ( 14) 22338( 18) 78036( 16) 45494( 13) 65995122) 49831 (17) 73608128) 57278( 19) 85 148 ( 24) 61982(17) 89298r21) 58457(28) 81761(28) 58271 ( 18) -8931 ( 12) 61781(15) -13748(16) 55698r28) 59997(26) -28984(19) 70272127) -23475(17) 76369 ( 2 4 ) 72 179 ( 2 8 ) 15933r 18) 527Br 19) 5671 1 1 16582 1241 268591 191 18837l41) 33913') -37133)
23003 ( 8 ) 3 1278 (9) 27204( 18)
28584( 1 1 ) 15491(14) 7405 ( 14) 8174(11) 1887( 18) 1698( 18) -5276 ( 1 1 ) -3449( 12) 4931(18) 9464( 18) 17881(11) 22175(12) 29777( 12) 30277( 18) 37899( 18) 37478( 18) 44262( 12) 42876( 12) 33885( 1 1 1 29066( 1 1 ) -5268( 18) -13389(12) -19782(12) -18123( 13) - 18 15 1 ( 14) -3888( 12) 58 15 ( 1 1 ) -3347( 13) -7538( 15) -3477 ( 16) 4877( 16) 9162( 13) 44264( 1 1 ) 52482( 13) 58927 ( 15) 57362( 15) 49457(28) 42826( 17) 33457 ( 1 1 ) 48128(15) 44126( 17) 41728( 18) 35 18 1 ( 19) 31818( 15) 2 3 6 8 8 ( 15) 27496( 18) 35343( 18) 38932( 18) 34761(15) 29593 ( 2 1 )
321(7) 351 (7) 381(7) 458(9) 455(9) 377(7) 353(7) 333(7) 352(8) 358(8) 338(7) 379(8) 387(8) 487(9) 479( 18)
1
-89(9) -137(13 -201 ( 1 1 52(6)
l 1
218L9) 39a1.11 114C11 1 3 1 13
163( 113 I70! 1 1 27131 13
24555(26)
-
aThe coordinates have been multiplied by l o 5 and the vibration coefficients by 10'. The Uij are coefficients in the expression exp[-2n2* ( U ,,a *2/z + . . . 2U, p *b *h k , . . ) ] . Lewis acid than the latter. The experimental binding constants for pyridine to these two compounds19support this thesis. T h e Z n - N ( P y ) distances found for ZnTPyP(Py),15 ZnTPC(Py) (this study), and ZnOEP(Py)20 form the series 2.143 (4), 2.171 (2), and 2.200 (3) A. An explanation of these observations is that steric interaction of the pyridine orthohydrogen atoms with the pyrrole rings result in lengthening of the Zn-Np, bond.20 The interaction would be largest if the hydrogen atoms were directly over two of the nitrogen atoms, 4 = Oo, and least for 4 of 4 5 O . T h e N(2)-Zn-N(5)-C(45) torsion angle, 4, is 18.6O in ZnTPC(Py) which is smaller than the 2 3 O found in ZnTPyP(Py) and larger than that of ZnOEP(Py), 4'. T h e distances of t h e nonhydrogen atoms of the chlorin system from their least-squares plane a r e given in Figure 4. C17 C34 C36 These indicate t h a t t h e molecule is saucer shaped as well a s c43 being slightly ruffled. T h e indivjdual pyrrole rings a r e planar t o within 0.01 A and no nonhydrogen atom of the reduced ring c53 C42 deviates from its best plane by more than 0.02 A. The hydrogen atoms of ring 1 a r e 0.74 8, above and below the best plane of Figure 2. The structure of 2,3-dihydro-a,P,y,rS-tetraphenylporphyrinathe pyrrole ring. The dihedral angles between the plane of the topyridinezinc(I1) and atom numbering systeni. The hydrogen atoms are four pyrrole N atoms and the planes of the four five-membered numbered according to the carbon atom to which they are bonded, The rings a r e all of the same sign and range between 3 and 6'. thermal ellipsoids are drawn for 50% probability, except for those ofhydrogen atoms which are not to scale. H(3B) is hidden behind C(3). There a r e two distortions exhibited by this molecule for
Journal of the American Chemical Society
/ 99:21 / October 12, 1977
692 1 N5
Table 111. Atomic Coordinates and Isotropic Thermal Vibration Parameters for the Hydrogen Atoms
IC-
96.P
2.90C
Figure 3. Coordination geometry
N3
of the zinc ion.
x
RTOM H12Al HI281 H13AI H(3B) Ht7) HISJ H ( 121 Hr131 Hr17J H I 181 H122) H(23) H124) H(25) H126)
4446125) 5454I283 3145128) 4869123) 1647122) 1893119) 4601(191 6882r21) 7519I23) 7 2 8 8 ( 13) 3393(19) 2049(22) 65(18) -583(24) 669(22)
H134J H(35) H136) H137) Hr38) H(48) H141) H1421
9683I29) 84291261 4817(221 5556124) 7455I24)
Y -2181121) -1744124) -2138(24) -1983r.19) 480(18) 2414(16) 5576116) 5594118) 2842119) 922r 161 -1206(16) -2638119) -3398(15) -2888(28) -141712'0) 41791 17) 5 3 2 5 ( 19) 6 198 ( 17) 577QI20) 46351171 4543(LO) 6037(21) 6 7 3 7 ( 19) 6166I24) 4752C21) -1193(18)
-2382120) -2354(20)
z
1958(17) 1374119) 723119) 121116) -976115) -605(14) 1958(13) 3415115) 4944(15) 4 4 9 8 ( 14) -1464(13) -2535116) -2245(12) -877(16) 196(16) - 6 1 8 ( 15) -1327(16) -6841 14) 8 2 5 I 17) 15241 14) 53981 17) 6512(18) 6151 115) 4734(28) 3784r18) 4173116) 4942117) 4545117)
B 80(7) 105I9) 102(9) 7316) 65(5) 55(5) 5115) 6516) 7116) 55(5) 53I5) 71(6) $6(4) r8(7) 73(6)
104(8) 87(7) 68(6) 3.3 A. There is no evidence of any T-T orbital interactions between neighboring molecules. The shortest distance between the planes of symmetry related chlorin systems is 3.92 A.
Figure 5. A packing diagram showing the environment of the benzene molecule and the interactions of the ZnTPC(Py) molecules. All molecules which have one or more atoms within 5 A from the centroid of the benzene molecule are drawn.
Spaulding, Andrews, Williams
/ 2,3-Dihydro-a.~.y,G-tetraphenylporphyrinatopyridinezinc(II~-Benzene
6922 Table IV. Bond Distances between Nonhydrogen Atoms']
Bond Zn-N(l) Zn-N(2) Zn-N(3) Zn-N(4) Zn-N ( 5 )
Type Zn-N
Distance
Meanb
2.130 (1) 2.060 (1) 2.072 ( I ) 2.065 2.063 (1) 2.073" 2.171 (2)
Saturated pyrrole N(I)-C(I) N(1 )-C(4) C(1)-C(2) C(3)-C(4) C(2)-C(3)
N-C, C,,-Cp Ca-C,j
1.366 (2) 1.384 (2) 1.373 (2) 1.374 (4ld 1.365 (2) 1.369 (9) 1.372 (2) 1.382 (2) 1.390 (2) 1.389 (2) I ,405 (2j 1.394 (2) 1.412 (2) 1.401 (4) 1.405 (2) 1.395 (2) 1.416 (2)
C,-C,j
Type
C(13)-C(14) C,-C,j C( 16)-C( 17) C(18)-C(19) C(7)-C(8) Cp-C$ C( 12)-C( 13) C( 17)-C( 18) C(9)-C(21) CMe-Cph C( lO)-C(27) C(15)-C(33) C(20)-C( 39)
1.362 (2) 1.363 1.364 (2) 1.497 (2) 1.495 1.493 (2) 1.478 (3)
Unsaturated pyrroles N(2)-C(6) N-C, ~(2)-~(9) N(3)-C(11) N ( 3)-C( 1 4) N(4)-C( 16) N(4)-C( 19) C(I)-C(20) C,-Cve
Bond
1.444 (3) 1.451 (2) 1.443 (2)
Distance 1.432 (3) 1.442 (3) 1.442 (2) 1.370 (3) 1.363 (3) 1.357 (3) 1.502 (2) 1.493 (3) 1.499 (2) 1.494 (3)
Meanb
Bond
Type
Distance Meanb
1.442 (2) C(34)-C(35) Co-Cm 1.447 (3)" C(37)-C(38) C(40)-C(41) C(43)-C(44) 1.362 C(23)-C(24) Cm-Cp 1.355'' C(24)-C(25) C(26)-C( 30) 1.497 (2) C(30)-C(31) 1.494 (4)' C(35)-C(36) C(36)-C(37)
1.392 (3) (1.392)' 1.394 (3) 1.397e 1.383 (4) 1.388 (4) 1.363 (3) 1.372 (3) 1.377 (4) 1.377 (4) 1.365 (9) 1.355 (4) (1.380)' 1.352 (4) 1 ,366' 1.355 (4) 1.367 (4)
C(4 1)-C(42) C(42)-C(43) Pyridine N(5)-C(45) ~ijj-c(49j
1.329 (3) 1.324 ( 3 j
C(45)-C(46) C(48)-C(49) C(46)-C(47) C(47)-C(48)
1.372 (3) 1.373 (3) 1.376 (4) 1.360 (4)
Benzene solvate C( 50)-c( 5 1 ) C(50)-C(55) C(51)-C(52) C(52)-C(53) C( 5 3) -C( 54) C(54)-C( 5 5 )
1.319 ( 5 ) 1.314 ( 7 ) 1.398 (6) 1.368 (7) 1.249 (6) 1.447 (8)
Phenyl rings
C(21)-C(22) Co-Cph C(21)-C(26) Ci27)-Ci28) 1.406 (6)" ci27j-ci32j C(33)-C(34) C(33)-C(38) C( 39)-C( 40) C(39)-C(44) C(22)-C(23) Co-Cm C(25)-C( 26) C(28)-C(29) C(31)-C(32)
1.383 (2) 1.388 (2) 1.383 (3) 1.389 (3) 1.378 (3) 1.372 (3) 1.393 (3) 1.382 (2) 1.388 (2) 1.379 (2) 1.384 (3) 1.390 (3)
1.383 (7) (1.399)c 1.387?
1.387 (4)
a Figures in parentheses are errors derived from the coordinate errors as obtained from the block-diagonal least-squares refinement. Unweighted averages for the chemically similar bonds are given along with their standard deviation, Ud, where ud = [Z(di - d ) ' ( n - 1 I n ] I / * . The average value of the indicated bonds after correction for rigid body motion. "From ZnTPyP(Py).lS eFrom SnTPPC12.I6
Table V. C-H Bond Lengths
C(2)-H(2A) C(2)-H(2B) C(3)-H(3A) C(4)-H(3B) C(7)-H(7) C(8)-H(8) C(12)-H(12) C(13)-H(13) C(17)-H(17) C(18)-H( 18) C(22)-H(22) C(23)-H(23) C(24)-H(24) C(25)-H(25) C(26)-H(26) C(28)-H(28) C(29)-H(29)
0.99(5) 0.99 (5) 1.07 ( 5 ) 0.93 (4) 0.93 (4) 0.94 (5) 1.00 (4) 0.98 (6) 0.99 (4) 0.97 ( 5 ) 0.98 (4) 0.99 (4) 1.05 (3) 1.02 (4) 1.04 (4) 1.06 ( 5 ) 1.07 ( 5 )
C(30)-H(30) C(31)-H(31) C(32)-H(32) C(34)-H(34) C(35)-H(35) C(36)-H(36) C(37)-H(37) C(38)-H(38) C(41)-H(41) C(42)--H(42) C(43)-H(43) C(44)-H(44) C(45)-H(45) C(46(-H(46) C(47)-(47) C(48)-H(48) C(49)-H(49)
1.02(5) 0.98 (4) 1 .oo (4) 1.05 ( 5 ) 1.16 ( 5 ) 1.05 (3) 0.98 ( 5 ) 0.96 ( 5 )
1.17 ( 5 ) 1.02 (6) 0.98 ( 5 ) 1.01 ( 5 ) 1.05 ( 5 ) 1.02 ( 5 ) 1.06 ( 5 ) 1.01 ( 5 )
1.06 ( 5 )
As can be seen from the stereoscopic packing diagram, Figure 5, the benzene molecule fits neatly into a hole formed
by the phenyl rings and the coordinated pyridine. T h e closest approaches of the benzene molecule to the macrocycle a r e given above. All remaining atomic contacts are >3.0 A. O n e of the reasons for undertaking this determination was to discern a structural basis for the large difference between the electron paramagnetic resonance hyperfine coupling constant (aH) of the aliphatic protons of the reduced ring in the cation radicals of zinctetraphenylchlorin (ZnTPC+.) and chlorophyll a (Chi+.). At 100 K, aH = 7.4 and 4.2 G for ZnTPC+. and Ch1+.,4,21respectively. This coupling is given by the McConnell equation,Z2 aH = (constant) p, cos2$ where pa is the unpaired spin density on the a-carbon atoms of the reduced ring and 0 is the dihedral angle between the plane containing the pz orbital lobes of C, and atom Co and the planes containing the atoms C,, Cp, and the hydrogen atoms bonded to Cp. Because of the planarity of ring I , the NC,CpHe torsion angles were used to calculate a n average value of 8 = 34 (4)O. Assuming 0 is the same in ZnTPC+. and ZnTPC, and using the theoretically calculated p, of 0.1 38, a value of aH = 7.9 G was predicted4 in reasonable agreement with the experimentally observed 7.4 G. If the spin densities a r e similar in
Journal of the American Chemical Society j 99:21 j October 12, 1977
6923 ZnTPC+. and Chi+-, then 6' should be larger in Chi+. than in Z ~ T P C + SFrom . ~ the x-ray structure of ethylchlorophyllide a5 a value for 6' = 45 (5)' was calculated confirming the trend suggested by the E S R data.
Table VI. Selected Bond Angles in Degrees',b
N(I)-Zn-N(2) NZnN (adjacent) N ( I)-Zn-N(4) N (2)-Zn-N (3) N( 3)-Zn-N (4) N(l)-Zn-N(3) NZnZ (opposite) N(2)-Zn-N(4) N ( I )-Zn-N ( 5 ) NZnNp, N (2)-Zn-N ( 5 ) Ti (3)-Zn-N(5) N (4)-Zn-N ( 5 ) C(l)-N(l)-C(4) Reduced ring N ( l)-C( 1)-C(2) N ( 1 ) -C( 4) -C( 3) C( I)-C(Z)-C(3) C( 2)-C( 3)-C(4) C(6)-Ti(2)-C(9) C"C,Y C ( l l)-N(3)-C(I4) C( 16)-N (4) -C( 19) Ti( I)-C(l)-C(20 N c,,cMe N(1)-C( I)-C(5) N(2)-C(6)-C(5) N(3)-C(I l)-C(lO) N(3)-C( l4)-C( 15) N(4)-C( 19)-C(20) C(4)-C(5)-C(6) CnCMeCn C(9)-C(IO)-C(I I ) C( 14)-C( 15)-C( 16) C( 19)-c(20)-c( I ) C(2O)-C( 1 )-C(2) C\leCc,C,j C(2O)-C(19)-C(18) C(5)-C(4)-C(3) C(5)-C(6)-C(7) C( 1 O)-C(S)-C(S) C( IO)-C( 1 I)-C(12) C ( 15)-C(14)-C(13) C(15)-C(16)-C(17) l\j (2) -C(6) -C (7) NC&j N(3)-C(I I)-C(12) N(3)-C( 14)-C(I 3) N(4)-C(16)-C(17) h(4)-C( l9)-C( 18) C(6)-C(7)-C(8) c, " C J3 C(9)-C@-C(7) C(I l)-C(I2)-C(l3) C(14)-C(13)-C(12) C( 16)-C( l7)-C( 18) C(19)-C(18)-C(17) C(4) -C( 5 ) -c(2 1 ) C,,CWeC,, C(6)-C(5)-C(21) C(9)-C( 10)-c(27) C(1 I)-C(lO)-C(27) C(14)-C(I5)-C(33) C( 16)-C( I5)-C(33) C( 19)-C(20)-C(39) C( I )-C(20)-C(39)
88.3 ( I ) 87.0 ( I ) 88.7 ( I ) 104.0 ( I ) 161.0 ( I ) 162.1 ( I ) 94.9 (1) 96.7 ( I ) 89.1 ( 1 )
Acknowledgments. W e wish to thank Dr. T . F. Koetzle for his critical suggestions and careful reading of the manuscript. O n e of us (L.C.A.) would like to thank Professor W . E. Love for his support. This work was carried out at Brookhaven National Laboratory under contract with the U S . Energy Research and Development Administration and supported by its Division of Physical Research. Additional support was received from the U S . National Science Foundation (Grant PCM75-18956), and the U S . National Institutes of Health (Grant 5RO1 A M I 6446-05).
101.0 ( I ) 108.7 ( I )
111.2(1) 1 1 1.3 ( I )
104.2 (2) 104.3 ( 1 ) 107.0 ( 1 ) 106.5 ( I ) 106.8 ( I ) 125.7 ( I ) 125.5 (2) 126.2 ( I ) 125.5 ( I ) 125.4 ( I ) 126.1 ( I ) 126.3 ( 1 ) 125.0 (2) 125.6 ( I ) 125.6 (2) 123.0 ( I ) 123.9 ( I ) 123.1 ( I ) 124.2 (1)
106.8 (2) 1O6.6lr 125.8 (3) 125.7"
124.5 (2) 124.7 (2) 124.7 ( I )
124.7 ( 1 ) 109.9 ( I ) 109.7 ( I ) 109.8 ( I ) 109.2 ( I ) 109.8 ( I ) 107.0 ( I ) 106.7 (2) 106.7 (2) 107.2 ( I ) 107.1 ( I ) 107.0 (2) 116.9 ( I ) 116.8 ( I ) 117.4 ( I ) 117.6 ( I ) 117.2(1) 117.1 ( I )
125.6 (3) 125.2r
124.1 (6)
125.7"
109.6 (3) 109.8"
106.9 (2) 106.9"
117.2(3) 117.3
117.5 ( I ) 116.8 ( I )
0 Figures in parentheses are errors derived from the coordinate errors as obtained from the block-diagonal least-squares refinement. Unweighted averages for the chemically similar bonds are given along with their standard deviation, Ud; where Ud = [ Z ( d l - d ) ' / ( n - l)n]1/2, From ZnTPyP(Py).]j
Spaulding, Andrews, Williams
Supplementary Material Available: A listing of structure amplitudes (33 pages). Ordering information is given on any current masthead Page.
References and Notes (1) Aspects of this work were previously presented: L. D. Spaulding, L. C. Andrews, J. Fajer and G. J. B. Williams, the 172nd National Meeting of the American Chemical Society, San Francisco, Calif., Aug 1976, Abstract iNOR 239. (2) (a) Applied Science; (b) Chemistry. (3) J. L. Hoard in "Porphyrins and Metalloporphyrins", K. M. Smith, Ed., Elsevier. New York. N.Y., 1975, Chapter 8. (4) J. Fajer, M. S. Davis, D. C. Brune, L. D. Spaulding, D. C. Borg, and A. Forman, Brookhaven Symp. Biol., 28, 74 (1976). (5) H . 4 . Chow, R. Serlin, and C. E. Strouse, J. Am. Chem. SOC.,97, 7230 (1975). (6) R. Serlin, H.-C. Chow, and C. E. Strouse, J. Am. Chem. Soc., 97, 7237 (1975). (7) H. W. Whitlock, R. Hanover, M. Y. Oester, and B. K. Bower, J. Am. Chem. SOC.,91, 7485 (1969). (8) H. W. Whitlock and M. Y. Oester, J. Am. Chem. SOC.,95, 5738 (1973). (9) D. T. Cromer and J. E. Mann, Acta Crystallogr. A, 24, 321 (1968). (10) D. T. Cromer and D. L. Liberman, J. Chem. Phys., 53, 1891 (1970). (1 1) Supplementary material available. See note at end of paper. (12) . . M. S.Fisher, D. H. TemDleton, A. Zalkin, and M. Calvin, J. Am. Chem. Soc., 94, 3413 (1972). (13) C. G. Pierpoint, R. C. Dickinson, and B. J. McCormick, lnorg. Chem., 13, 1674 (1974). (14) Y. Mitsui, M. Tsuboi, and Y. litaka, Acta Crystallogr., Sect. B, 25, 2182 (1969). (15) D. M. Collins and J. L. Hoard, J. Am. Chem. SOC., 92, 3761 (1970). (16) D. M. Collins, W. R. Scheidt, and J. L. Hoard, J. Am. Chem. Soc., 94, 6689 (1972). (17) D. H. Karweik and N. Winograd, lnorg. Chem., 15, 2336 (1976). (18) M. Gouterman, C. H. Wagniere, and L. C. Snyder, J. Mol. Spectrosc., 11, 108 (1963). (19) J. E. Falk, "Porphyrins and Metalioporphyrins", Elsevier. New York, N.Y. 1964, p 41. (20) D. L. Cullen and E. F. Meyer, Acta Crystallogr., Sect. 6,32, 2259 (1976). (21) J. R. Norris. H. Scheer, M. E. Druyan, and J. J. Katz, Proc. Natl. Acad. Sci. USA 71,4897 (1974). (22) H. M. McConnell, J. Chem. Phys., 24, 764 (1956). (23) Programs are described in "Brookhaven National Laboratory, Chemistry Department, CRYSNET Manual", H. M. Berman, F. C. Bernstein, H. J. Bernstein, T. F. Koetzle, and G. J. B. Williams, Eds. (Informal Report, BNL 21714, 1976). (24) V. Schomaker and K. N. Trueblood, Acta Crystallogr., Sect. 8,24, 63 (1968). (25) J. M. Stewart, G. J. Kruger. H. L. Ammon, C. Dickinson. and S. R. Hall, Technical Report TR-192, Computer Science Center, University of Maryland, 1976.
1 2,3-Dihydro-c~,P,y,G-tetraphenylporphyrinatopyridinezinc(II~-Benzene
