Crystallization (from ethyl acetate solution) of 2-(4-chlorophenyl)-4-methylchromenium perchlorate, C
16H
12ClO
+·;ClO
4−, (I), yields two monoclinic polymorphs with the space groups
P2
1/
n [polymorph (I
a)] and
P2
1/
c [polymorph (I
b)]; in both cases,
Z = 4. Cations and anions, disordered in polymorph (I
b), form ion pairs in both polymorphs as a result of Cl—O
π interactions. Related by a centre of symmetry, neighbouring ion pairs in polymorph (I
a) are linked
via π–π interactions between cationic fragments, and the resulting dimers are linked through a network of C—H
O(perchlorate) interactions between adjacent cations and anions. The ion pairs in polymorph (I
b), arranged in pairs of columns along the
a axis, are linked through a network of C—H
O(perchlorate), C—Cl
π, π–π and C—Cl
O(perchlorate) interactions. The aromatic skeletons in polymorph (I
a) are parallel in the cationic fragments involved in dimers, but nonparallel in adjacent ion pairs not constituting dimers. In polymorph (I
b), these skeletons are parallel in pairs of columns, but nonparallel in adjacent pairs of columns; this is visible as a herring-bone pattern. Differences in the crystal structures of the polymorphs are most probably the cause of their different colours.
Supporting information
CCDC references: 669178; 669179
Compound (I) was synthesized by the method described in the literature (Czerney et al., 1995). The crude product was purified by recrystallization, initially from concentrated acetic acid and then from dichloromethane. The purity of the compound was confirmed chromatographically and its identity proven by IR and NMR spectroscopy. Crystals of the polymorphic forms (Ia) and (Ib) suitable for X-ray investigations were grown from ethyl acetate. They were separated manually.
All H atoms were positioned geometrically and refined using a riding model, with C—H distances of 0.93 Å and with Uiso(H) = 1.2Ueq(C), or C—H = 0.96 Å and Uiso(H) = 1.5Ueq(C) for the methyl group. The atoms of the perchlorate anion in polymorph (Ib) were located in a difference Fourier map and refined to an ideal tetrahedron, with restrained standard deviations of 0.01 and 0.03 Å for the Cl—O and O···O distances, respectively (SADI instruction in SHELXL97; Sheldrick, 1997) (Müller et al., 2006). Following refinement, the anisotropic displacement parameters of adjacent atoms were restrained to be similar (SIMU instruction), and the main directions of movements of covalently bonded atoms were likewise restrained (DELU instruction) (Müller et al., 2006). The occupancy ratio was determined by isotropic refinement for the disordered site and was refined freely during subsequent anisotropic refinement.
For both compounds, data collection: P3 (Siemens, 1989); cell refinement: P3; data reduction: XDISK (Siemens, 1991); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003).
(Ia) 2-(4-chlorophenyl)-4-methylchromenium perchlorate
top
Crystal data top
C16H12ClO+·ClO4− | F(000) = 728 |
Mr = 355.16 | Dx = 1.489 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 50 reflections |
a = 11.0290 (19) Å | θ = 2.5–25.0° |
b = 12.817 (2) Å | µ = 0.43 mm−1 |
c = 11.2083 (18) Å | T = 290 K |
β = 90.173 (13)° | Prism, green |
V = 1584.4 (4) Å3 | 0.3 × 0.3 × 0.2 mm |
Z = 4 | |
Data collection top
Siemens P3/PC diffractometer | Rint = 0.025 |
Radiation source: fine-focus sealed X-ray tube | θmax = 25.0°, θmin = 2.5° |
Graphite monochromator | h = 0→13 |
θ/2θ scans | k = 0→15 |
2915 measured reflections | l = −13→13 |
2763 independent reflections | 2 standard reflections every 98 reflections |
2124 reflections with I > 2σ(I) | intensity decay: 1.5% |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.042 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.126 | H-atom parameters constrained |
S = 0.92 | w = 1/[σ2(Fo2) + (0.0902P)2] where P = (Fo2 + 2Fc2)/3 |
2763 reflections | (Δ/σ)max < 0.001 |
208 parameters | Δρmax = 0.32 e Å−3 |
0 restraints | Δρmin = −0.22 e Å−3 |
Crystal data top
C16H12ClO+·ClO4− | V = 1584.4 (4) Å3 |
Mr = 355.16 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 11.0290 (19) Å | µ = 0.43 mm−1 |
b = 12.817 (2) Å | T = 290 K |
c = 11.2083 (18) Å | 0.3 × 0.3 × 0.2 mm |
β = 90.173 (13)° | |
Data collection top
Siemens P3/PC diffractometer | Rint = 0.025 |
2915 measured reflections | 2 standard reflections every 98 reflections |
2763 independent reflections | intensity decay: 1.5% |
2124 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.126 | H-atom parameters constrained |
S = 0.92 | Δρmax = 0.32 e Å−3 |
2763 reflections | Δρmin = −0.22 e Å−3 |
208 parameters | |
Special details top
Experimental. no |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.09592 (13) | 0.68936 (11) | 0.94168 (11) | 0.0614 (3) | |
C2 | 0.13088 (16) | 0.59227 (15) | 0.91970 (17) | 0.0545 (4) | |
C3 | 0.1407 (2) | 0.55907 (19) | 0.80202 (18) | 0.0672 (5) | |
H3 | 0.1632 | 0.4904 | 0.7869 | 0.081* | |
C4 | 0.1183 (2) | 0.62429 (19) | 0.70753 (19) | 0.0704 (6) | |
C5 | 0.0521 (2) | 0.8057 (2) | 0.6461 (2) | 0.0793 (7) | |
H5 | 0.0581 | 0.7897 | 0.5654 | 0.095* | |
C6 | 0.0176 (3) | 0.9017 (2) | 0.6788 (2) | 0.0907 (8) | |
H6 | −0.0013 | 0.9506 | 0.6203 | 0.109* | |
C7 | 0.0093 (3) | 0.9297 (2) | 0.7986 (3) | 0.0936 (8) | |
H7 | −0.0132 | 0.9972 | 0.8195 | 0.112* | |
C8 | 0.0348 (2) | 0.85690 (18) | 0.8865 (2) | 0.0808 (7) | |
H8 | 0.0279 | 0.8742 | 0.9668 | 0.097* | |
C9 | 0.07982 (19) | 0.72788 (18) | 0.73236 (19) | 0.0653 (5) | |
C10 | 0.07050 (18) | 0.75861 (16) | 0.85244 (18) | 0.0595 (5) | |
C11 | 0.15580 (16) | 0.53298 (14) | 1.02693 (16) | 0.0526 (4) | |
C12 | 0.1498 (2) | 0.57924 (16) | 1.13823 (18) | 0.0650 (5) | |
H12 | 0.1295 | 0.6495 | 1.1440 | 0.078* | |
C13 | 0.1733 (2) | 0.52337 (17) | 1.24071 (18) | 0.0693 (6) | |
H13 | 0.1692 | 0.5563 | 1.3146 | 0.083* | |
C14 | 0.20250 (19) | 0.42021 (17) | 1.23452 (18) | 0.0638 (5) | |
C15 | 0.2072 (2) | 0.36938 (18) | 1.1256 (2) | 0.0738 (6) | |
H15 | 0.2258 | 0.2987 | 1.1219 | 0.089* | |
C16 | 0.1841 (2) | 0.42479 (19) | 1.0230 (2) | 0.0769 (6) | |
H16 | 0.1870 | 0.3909 | 0.9497 | 0.092* | |
Cl17 | 0.22578 (7) | 0.35059 (5) | 1.36519 (6) | 0.0909 (2) | |
C18 | 0.1368 (3) | 0.5869 (2) | 0.5827 (2) | 0.0977 (9) | |
H18A | 0.1613 | 0.5150 | 0.5840 | 0.147* | |
H18B | 0.1985 | 0.6281 | 0.5452 | 0.147* | |
H18C | 0.0623 | 0.5935 | 0.5388 | 0.147* | |
Cl19 | 0.07323 (5) | 0.23683 (4) | 0.69382 (4) | 0.06254 (15) | |
O20 | 0.1157 (3) | 0.1597 (2) | 0.6167 (2) | 0.1595 (11) | |
O21 | −0.04263 (19) | 0.2684 (2) | 0.6605 (2) | 0.1340 (9) | |
O22 | 0.1506 (3) | 0.3190 (3) | 0.6782 (4) | 0.1879 (14) | |
O23 | 0.0822 (3) | 0.2113 (3) | 0.8119 (2) | 0.1573 (11) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0699 (8) | 0.0664 (8) | 0.0479 (7) | 0.0041 (7) | 0.0012 (6) | −0.0047 (6) |
C2 | 0.0478 (9) | 0.0612 (10) | 0.0544 (10) | −0.0062 (8) | −0.0003 (8) | −0.0111 (9) |
C3 | 0.0696 (12) | 0.0781 (13) | 0.0539 (11) | −0.0048 (11) | −0.0034 (9) | −0.0108 (10) |
C4 | 0.0767 (13) | 0.0829 (14) | 0.0516 (11) | −0.0109 (11) | −0.0049 (10) | −0.0141 (10) |
C5 | 0.0929 (17) | 0.0912 (16) | 0.0539 (12) | −0.0090 (14) | −0.0063 (11) | 0.0083 (11) |
C6 | 0.112 (2) | 0.0795 (16) | 0.0801 (16) | −0.0020 (15) | −0.0172 (14) | 0.0196 (13) |
C7 | 0.119 (2) | 0.0760 (15) | 0.0851 (17) | 0.0094 (15) | −0.0087 (16) | 0.0047 (13) |
C8 | 0.0989 (18) | 0.0745 (14) | 0.0690 (14) | 0.0144 (13) | −0.0029 (13) | −0.0021 (11) |
C9 | 0.0591 (11) | 0.0845 (14) | 0.0521 (10) | −0.0147 (10) | −0.0040 (9) | −0.0016 (10) |
C10 | 0.0595 (11) | 0.0634 (11) | 0.0555 (11) | −0.0014 (9) | −0.0049 (9) | −0.0014 (9) |
C11 | 0.0518 (10) | 0.0547 (10) | 0.0514 (10) | −0.0033 (8) | 0.0028 (8) | −0.0070 (8) |
C12 | 0.0900 (14) | 0.0498 (10) | 0.0553 (11) | −0.0033 (10) | −0.0013 (10) | −0.0037 (8) |
C13 | 0.0933 (16) | 0.0619 (12) | 0.0527 (11) | 0.0068 (11) | −0.0006 (10) | −0.0085 (9) |
C14 | 0.0621 (11) | 0.0700 (13) | 0.0593 (11) | 0.0040 (10) | 0.0005 (9) | 0.0039 (10) |
C15 | 0.0822 (14) | 0.0623 (12) | 0.0769 (15) | 0.0198 (11) | −0.0052 (11) | −0.0027 (10) |
C16 | 0.0888 (15) | 0.0805 (15) | 0.0613 (12) | 0.0219 (12) | 0.0000 (11) | −0.0171 (11) |
Cl17 | 0.1089 (5) | 0.0873 (4) | 0.0766 (4) | 0.0176 (3) | −0.0068 (3) | 0.0198 (3) |
C18 | 0.140 (2) | 0.1014 (19) | 0.0517 (13) | −0.0027 (18) | 0.0002 (14) | −0.0132 (13) |
Cl19 | 0.0679 (3) | 0.0617 (3) | 0.0580 (3) | 0.0092 (2) | −0.0010 (2) | −0.0016 (2) |
O20 | 0.191 (2) | 0.164 (2) | 0.1225 (18) | 0.1124 (18) | −0.0411 (16) | −0.0622 (15) |
O21 | 0.0861 (13) | 0.212 (2) | 0.1038 (15) | 0.0527 (14) | −0.0201 (11) | −0.0522 (16) |
O22 | 0.182 (3) | 0.152 (2) | 0.231 (4) | −0.084 (2) | 0.014 (3) | 0.012 (2) |
O23 | 0.209 (3) | 0.188 (3) | 0.0755 (14) | 0.049 (2) | −0.0073 (16) | 0.0258 (16) |
Geometric parameters (Å, º) top
O1—C2 | 1.326 (2) | C11—C12 | 1.383 (3) |
O1—C10 | 1.366 (2) | C11—C16 | 1.422 (3) |
C2—C3 | 1.390 (3) | C12—C13 | 1.377 (3) |
C2—C11 | 1.448 (3) | C12—H12 | 0.9300 |
C3—C4 | 1.371 (3) | C13—C14 | 1.363 (3) |
C3—H3 | 0.9300 | C13—H13 | 0.9300 |
C4—C9 | 1.422 (3) | C14—C15 | 1.385 (3) |
C4—C18 | 1.493 (3) | C14—Cl17 | 1.733 (2) |
C5—C6 | 1.339 (4) | C15—C16 | 1.375 (3) |
C5—C9 | 1.422 (3) | C15—H15 | 0.9300 |
C5—H5 | 0.9300 | C16—H16 | 0.9300 |
C6—C7 | 1.394 (4) | C18—H18A | 0.9600 |
C6—H6 | 0.9300 | C18—H18B | 0.9600 |
C7—C8 | 1.385 (4) | C18—H18C | 0.9600 |
C7—H7 | 0.9300 | Cl19—O23 | 1.367 (2) |
C8—C10 | 1.374 (3) | Cl19—O22 | 1.368 (3) |
C8—H8 | 0.9300 | Cl19—O21 | 1.391 (2) |
C9—C10 | 1.406 (3) | Cl19—O20 | 1.395 (2) |
| | | |
O1—C2—C3 | 119.13 (18) | C12—C11—C2 | 120.96 (17) |
O1—C2—C11 | 113.14 (15) | C16—C11—C2 | 121.82 (18) |
C2—O1—C10 | 122.21 (15) | C13—C12—C11 | 121.33 (19) |
C3—C2—C11 | 127.72 (19) | C13—C12—H12 | 119.3 |
C4—C3—C2 | 122.1 (2) | C11—C12—H12 | 119.3 |
C4—C3—H3 | 118.9 | C14—C13—C12 | 120.4 (2) |
C2—C3—H3 | 118.9 | C14—C13—H13 | 119.8 |
C3—C4—C9 | 118.1 (2) | C12—C13—H13 | 119.8 |
C3—C4—C18 | 120.2 (2) | C13—C14—C15 | 120.7 (2) |
C9—C4—C18 | 121.7 (2) | C13—C14—Cl17 | 119.40 (17) |
C6—C5—C9 | 121.3 (2) | C15—C14—Cl17 | 119.79 (17) |
C6—C5—H5 | 119.4 | C16—C15—C14 | 119.1 (2) |
C9—C5—H5 | 119.4 | C16—C15—H15 | 120.4 |
C5—C6—C7 | 121.3 (2) | C14—C15—H15 | 120.4 |
C5—C6—H6 | 119.3 | C15—C16—C11 | 121.2 (2) |
C7—C6—H6 | 119.3 | C15—C16—H16 | 119.4 |
C8—C7—C6 | 119.9 (3) | C11—C16—H16 | 119.4 |
C8—C7—H7 | 120.1 | C4—C18—H18A | 109.5 |
C6—C7—H7 | 120.1 | C4—C18—H18B | 109.5 |
C10—C8—C7 | 118.5 (2) | H18A—C18—H18B | 109.5 |
C10—C8—H8 | 120.7 | C4—C18—H18C | 109.5 |
C7—C8—H8 | 120.7 | H18A—C18—H18C | 109.5 |
C10—C9—C4 | 118.1 (2) | H18B—C18—H18C | 109.5 |
C10—C9—C5 | 116.0 (2) | O23—Cl19—O22 | 105.4 (2) |
C4—C9—C5 | 125.9 (2) | O23—Cl19—O21 | 113.19 (17) |
O1—C10—C8 | 116.78 (19) | O22—Cl19—O21 | 108.3 (2) |
O1—C10—C9 | 120.22 (18) | O23—Cl19—O20 | 113.99 (17) |
C8—C10—C9 | 123.0 (2) | O22—Cl19—O20 | 104.8 (2) |
C12—C11—C16 | 117.20 (19) | O21—Cl19—O20 | 110.47 (15) |
| | | |
C10—O1—C2—C3 | −0.8 (3) | C4—C9—C10—O1 | −1.2 (3) |
C10—O1—C2—C11 | 178.63 (16) | C5—C9—C10—O1 | −179.68 (18) |
O1—C2—C3—C4 | 1.7 (3) | C4—C9—C10—C8 | 179.7 (2) |
C11—C2—C3—C4 | −177.7 (2) | C5—C9—C10—C8 | 1.2 (3) |
C2—C3—C4—C9 | −2.2 (3) | O1—C2—C11—C12 | −3.9 (3) |
C2—C3—C4—C18 | 176.5 (2) | C3—C2—C11—C12 | 175.5 (2) |
C9—C5—C6—C7 | 1.1 (4) | O1—C2—C11—C16 | 174.38 (18) |
C5—C6—C7—C8 | −1.3 (5) | C3—C2—C11—C16 | −6.2 (3) |
C6—C7—C8—C10 | 1.4 (4) | C16—C11—C12—C13 | 1.6 (3) |
C3—C4—C9—C10 | 1.9 (3) | C2—C11—C12—C13 | 179.96 (19) |
C18—C4—C9—C10 | −176.8 (2) | C11—C12—C13—C14 | −0.4 (4) |
C3—C4—C9—C5 | −179.7 (2) | C12—C13—C14—C15 | −1.0 (4) |
C18—C4—C9—C5 | 1.5 (4) | C12—C13—C14—Cl17 | −177.48 (18) |
C6—C5—C9—C10 | −1.0 (4) | C13—C14—C15—C16 | 1.1 (4) |
C6—C5—C9—C4 | −179.3 (2) | C16—C15—C14—Cl17 | 177.59 (19) |
C2—O1—C10—C8 | 179.83 (19) | C14—C15—C16—C11 | 0.1 (4) |
C2—O1—C10—C9 | 0.6 (3) | C12—C11—C16—C15 | −1.5 (3) |
C7—C8—C10—O1 | 179.4 (2) | C2—C11—C16—C15 | −179.8 (2) |
C7—C8—C10—C9 | −1.4 (4) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O22 | 0.93 | 2.52 | 3.377 (5) | 154 |
(Ib) 2-(4-chlorophenyl)-4-methylchromenium perchlorate
top
Crystal data top
C16H12ClO+·ClO4− | F(000) = 728 |
Mr = 355.16 | Dx = 1.497 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 50 reflections |
a = 8.0631 (15) Å | θ = 2.5–25.0° |
b = 11.873 (3) Å | µ = 0.43 mm−1 |
c = 16.487 (2) Å | T = 290 K |
β = 93.292 (14)° | Prism, olive-green |
V = 1575.8 (5) Å3 | 0.5 × 0.4 × 0.3 mm |
Z = 4 | |
Data collection top
Siemens P3/PC diffractometer | Rint = 0.036 |
Radiation source: fine-focus sealed X-ray tube | θmax = 25.0°, θmin = 3.0° |
Graphite monochromator | h = 0→9 |
θ/2θ scans | k = 0→14 |
2957 measured reflections | l = −19→19 |
2748 independent reflections | 3 standard reflections every 200 reflections |
1814 reflections with I > 2σ(I) | intensity decay: 2.0% |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.049 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.123 | H-atom parameters constrained |
S = 0.85 | w = 1/[σ2(Fo2) + (0.0849P)2] where P = (Fo2 + 2Fc2)/3 |
2748 reflections | (Δ/σ)max < 0.001 |
255 parameters | Δρmax = 0.20 e Å−3 |
261 restraints | Δρmin = −0.26 e Å−3 |
Crystal data top
C16H12ClO+·ClO4− | V = 1575.8 (5) Å3 |
Mr = 355.16 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 8.0631 (15) Å | µ = 0.43 mm−1 |
b = 11.873 (3) Å | T = 290 K |
c = 16.487 (2) Å | 0.5 × 0.4 × 0.3 mm |
β = 93.292 (14)° | |
Data collection top
Siemens P3/PC diffractometer | Rint = 0.036 |
2957 measured reflections | 3 standard reflections every 200 reflections |
2748 independent reflections | intensity decay: 2.0% |
1814 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.049 | 261 restraints |
wR(F2) = 0.123 | H-atom parameters constrained |
S = 0.85 | Δρmax = 0.20 e Å−3 |
2748 reflections | Δρmin = −0.26 e Å−3 |
255 parameters | |
Special details top
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
O1 | 0.2075 (4) | 0.2599 (3) | 0.0201 (2) | 0.0598 (10) | |
C2 | 0.3229 (6) | 0.2015 (4) | 0.0620 (3) | 0.0535 (12) | |
C3 | 0.2964 (7) | 0.1688 (5) | 0.1409 (3) | 0.0594 (13) | |
H3 | 0.3769 | 0.1260 | 0.1693 | 0.071* | |
C4 | 0.1551 (7) | 0.1978 (5) | 0.1782 (3) | 0.0620 (14) | |
C5 | −0.1185 (7) | 0.3010 (6) | 0.1628 (4) | 0.0756 (18) | |
H5 | −0.1460 | 0.2836 | 0.2154 | 0.091* | |
C6 | −0.2228 (7) | 0.3635 (6) | 0.1144 (5) | 0.0808 (19) | |
H6 | −0.3218 | 0.3884 | 0.1345 | 0.097* | |
C7 | −0.1882 (8) | 0.3913 (6) | 0.0372 (5) | 0.0788 (18) | |
H7 | −0.2633 | 0.4349 | 0.0059 | 0.095* | |
C8 | −0.0461 (7) | 0.3565 (5) | 0.0050 (4) | 0.0680 (15) | |
H8 | −0.0225 | 0.3750 | −0.0479 | 0.082* | |
C9 | 0.0331 (6) | 0.2617 (5) | 0.1336 (3) | 0.0586 (14) | |
C10 | 0.0627 (6) | 0.2925 (4) | 0.0538 (3) | 0.0540 (12) | |
C11 | 0.4674 (6) | 0.1736 (4) | 0.0170 (3) | 0.0547 (13) | |
C12 | 0.4785 (7) | 0.2071 (6) | −0.0632 (4) | 0.0743 (17) | |
H12 | 0.3918 | 0.2480 | −0.0885 | 0.089* | |
C13 | 0.6150 (8) | 0.1812 (6) | −0.1060 (4) | 0.0733 (17) | |
H13 | 0.6200 | 0.2025 | −0.1601 | 0.088* | |
C14 | 0.7415 (6) | 0.1241 (5) | −0.0676 (3) | 0.0586 (13) | |
C15 | 0.7351 (7) | 0.0868 (5) | 0.0110 (4) | 0.0661 (15) | |
H15 | 0.8223 | 0.0454 | 0.0354 | 0.079* | |
C16 | 0.5967 (7) | 0.1117 (5) | 0.0532 (3) | 0.0598 (14) | |
H16 | 0.5904 | 0.0867 | 0.1064 | 0.072* | |
Cl17 | 0.9189 (2) | 0.09293 (14) | −0.12047 (11) | 0.0814 (6) | |
C18 | 0.1337 (9) | 0.1610 (7) | 0.2631 (4) | 0.086 (2) | |
H18C | 0.2286 | 0.1178 | 0.2823 | 0.130* | |
H18B | 0.0354 | 0.1156 | 0.2648 | 0.130* | |
H18A | 0.1232 | 0.2260 | 0.2971 | 0.130* | |
Cl19 | 0.3290 (14) | 0.4978 (8) | 0.2129 (8) | 0.062 (3) | 0.557 (13) |
O20 | 0.4875 (15) | 0.4668 (16) | 0.2428 (9) | 0.140 (5) | 0.557 (13) |
O21 | 0.347 (2) | 0.6112 (10) | 0.2286 (10) | 0.134 (5) | 0.557 (13) |
O22 | 0.218 (2) | 0.4929 (15) | 0.1468 (8) | 0.145 (6) | 0.557 (13) |
O23 | 0.2414 (16) | 0.4457 (10) | 0.2719 (6) | 0.126 (5) | 0.557 (13) |
Cl9A | 0.3313 (17) | 0.4974 (12) | 0.2044 (11) | 0.072 (4) | 0.443 (13) |
O20A | 0.454 (2) | 0.5737 (16) | 0.2278 (12) | 0.116 (6) | 0.443 (13) |
O21A | 0.216 (2) | 0.5735 (14) | 0.1764 (11) | 0.121 (5) | 0.443 (13) |
O22A | 0.3500 (19) | 0.4442 (11) | 0.1304 (8) | 0.104 (5) | 0.443 (13) |
O23A | 0.410 (2) | 0.4010 (13) | 0.2292 (12) | 0.135 (6) | 0.443 (13) |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.060 (2) | 0.061 (2) | 0.058 (2) | −0.0049 (18) | −0.0038 (17) | 0.0004 (17) |
C2 | 0.050 (3) | 0.056 (3) | 0.054 (3) | −0.010 (2) | −0.006 (2) | 0.001 (2) |
C3 | 0.060 (3) | 0.065 (3) | 0.053 (3) | −0.002 (3) | −0.006 (2) | 0.009 (2) |
C4 | 0.060 (3) | 0.068 (3) | 0.058 (3) | −0.013 (3) | 0.003 (3) | −0.011 (3) |
C5 | 0.064 (4) | 0.082 (4) | 0.081 (4) | −0.021 (3) | 0.006 (3) | −0.025 (3) |
C6 | 0.051 (3) | 0.096 (5) | 0.096 (5) | 0.005 (3) | 0.001 (3) | −0.024 (4) |
C7 | 0.069 (4) | 0.071 (4) | 0.095 (5) | 0.004 (3) | −0.014 (3) | −0.007 (4) |
C8 | 0.065 (4) | 0.067 (4) | 0.071 (4) | −0.001 (3) | −0.002 (3) | −0.008 (3) |
C9 | 0.053 (3) | 0.060 (3) | 0.063 (3) | −0.015 (3) | 0.001 (2) | −0.016 (3) |
C10 | 0.053 (3) | 0.051 (3) | 0.057 (3) | −0.005 (2) | −0.009 (2) | −0.008 (2) |
C11 | 0.058 (3) | 0.051 (3) | 0.054 (3) | −0.005 (2) | −0.001 (2) | −0.003 (2) |
C12 | 0.062 (3) | 0.100 (5) | 0.061 (3) | 0.004 (3) | 0.009 (3) | 0.029 (3) |
C13 | 0.076 (4) | 0.093 (5) | 0.052 (3) | 0.004 (3) | 0.014 (3) | 0.023 (3) |
C14 | 0.058 (3) | 0.063 (3) | 0.056 (3) | −0.014 (3) | 0.011 (2) | −0.002 (3) |
C15 | 0.065 (3) | 0.062 (3) | 0.070 (4) | −0.002 (3) | −0.003 (3) | −0.008 (3) |
C16 | 0.066 (3) | 0.056 (3) | 0.056 (3) | −0.005 (3) | −0.008 (3) | 0.006 (2) |
Cl17 | 0.0782 (10) | 0.0779 (11) | 0.0906 (12) | −0.0014 (8) | 0.0272 (8) | 0.0017 (8) |
C18 | 0.098 (5) | 0.102 (5) | 0.059 (4) | −0.005 (4) | 0.010 (3) | 0.005 (3) |
Cl19 | 0.064 (5) | 0.055 (4) | 0.067 (4) | 0.003 (4) | 0.002 (3) | −0.008 (3) |
O20 | 0.122 (9) | 0.158 (15) | 0.139 (11) | −0.013 (9) | −0.004 (7) | 0.006 (10) |
O21 | 0.173 (15) | 0.104 (9) | 0.124 (10) | −0.025 (8) | 0.001 (11) | −0.016 (7) |
O22 | 0.179 (14) | 0.144 (14) | 0.108 (9) | −0.066 (13) | −0.024 (10) | −0.006 (9) |
O23 | 0.142 (10) | 0.132 (9) | 0.104 (8) | −0.045 (8) | 0.002 (7) | 0.006 (6) |
Cl9A | 0.065 (7) | 0.074 (7) | 0.075 (6) | −0.016 (5) | −0.008 (4) | −0.016 (4) |
O20A | 0.114 (11) | 0.106 (12) | 0.126 (12) | −0.027 (10) | −0.016 (11) | −0.011 (10) |
O21A | 0.116 (11) | 0.120 (12) | 0.126 (13) | −0.001 (9) | −0.008 (9) | 0.000 (10) |
O22A | 0.105 (10) | 0.103 (10) | 0.103 (8) | −0.028 (7) | 0.007 (7) | −0.021 (6) |
O23A | 0.146 (15) | 0.101 (10) | 0.156 (12) | −0.035 (9) | −0.021 (11) | 0.012 (10) |
Geometric parameters (Å, º) top
O1—C2 | 1.323 (6) | C12—H12 | 0.9300 |
O1—C10 | 1.376 (6) | C13—C14 | 1.351 (8) |
C2—C3 | 1.386 (7) | C13—H13 | 0.9300 |
C2—C11 | 1.455 (7) | C14—C15 | 1.374 (8) |
C3—C4 | 1.369 (8) | C14—Cl17 | 1.757 (5) |
C3—H3 | 0.9300 | C15—C16 | 1.381 (8) |
C4—C9 | 1.415 (8) | C15—H15 | 0.9300 |
C4—C18 | 1.485 (8) | C16—H16 | 0.9300 |
C5—C6 | 1.349 (9) | C18—H18C | 0.9600 |
C5—C9 | 1.418 (8) | C18—H18B | 0.9600 |
C5—H5 | 0.9300 | C18—H18A | 0.9600 |
C6—C7 | 1.359 (9) | Cl19—O22 | 1.370 (11) |
C6—H6 | 0.9300 | Cl19—O21 | 1.377 (11) |
C7—C8 | 1.355 (8) | Cl19—O23 | 1.380 (13) |
C7—H7 | 0.9300 | Cl19—O20 | 1.393 (11) |
C8—C10 | 1.383 (8) | Cl9A—O21A | 1.360 (12) |
C8—H8 | 0.9300 | Cl9A—O23A | 1.360 (13) |
C9—C10 | 1.400 (8) | Cl9A—O20A | 1.382 (13) |
C11—C16 | 1.383 (7) | Cl9A—O22A | 1.390 (14) |
C11—C12 | 1.388 (8) | O22A—O23A | 1.75 (2) |
C12—C13 | 1.376 (8) | | |
| | | |
O1—C2—C3 | 119.7 (5) | C11—C12—H12 | 119.3 |
O1—C2—C11 | 114.4 (4) | C14—C13—C12 | 118.5 (5) |
C2—O1—C10 | 121.6 (4) | C14—C13—H13 | 120.7 |
C3—C2—C11 | 125.9 (5) | C12—C13—H13 | 120.7 |
C4—C3—C2 | 121.9 (5) | C13—C14—C15 | 122.3 (5) |
C4—C3—H3 | 119.0 | C13—C14—Cl17 | 119.2 (4) |
C2—C3—H3 | 119.0 | C15—C14—Cl17 | 118.4 (5) |
C3—C4—C9 | 118.2 (5) | C14—C15—C16 | 118.8 (6) |
C3—C4—C18 | 119.7 (6) | C14—C15—H15 | 120.6 |
C9—C4—C18 | 122.1 (5) | C16—C15—H15 | 120.6 |
C6—C5—C9 | 120.0 (6) | C15—C16—C11 | 120.5 (5) |
C6—C5—H5 | 120.0 | C15—C16—H16 | 119.8 |
C9—C5—H5 | 120.0 | C11—C16—H16 | 119.8 |
C5—C6—C7 | 122.3 (6) | C4—C18—H18C | 109.5 |
C5—C6—H6 | 118.9 | C4—C18—H18B | 109.5 |
C7—C6—H6 | 118.9 | H18C—C18—H18B | 109.5 |
C8—C7—C6 | 121.1 (6) | C4—C18—H18A | 109.5 |
C8—C7—H7 | 119.5 | H18C—C18—H18A | 109.5 |
C6—C7—H7 | 119.5 | H18B—C18—H18A | 109.5 |
C7—C8—C10 | 117.6 (6) | O22—Cl19—O21 | 104.3 (11) |
C7—C8—H8 | 121.2 | O22—Cl19—O23 | 101.8 (11) |
C10—C8—H8 | 121.2 | O21—Cl19—O23 | 111.0 (11) |
C10—C9—C4 | 118.5 (5) | O22—Cl19—O20 | 144.4 (16) |
C10—C9—C5 | 115.5 (5) | O21—Cl19—O20 | 96.3 (11) |
C4—C9—C5 | 125.9 (6) | O23—Cl19—O20 | 97.4 (11) |
O1—C10—C8 | 116.4 (5) | O21A—Cl9A—O23A | 163.7 (15) |
O1—C10—C9 | 120.0 (5) | O21A—Cl9A—O20A | 97.3 (13) |
C8—C10—C9 | 123.6 (5) | O23A—Cl9A—O20A | 98.8 (13) |
C16—C11—C12 | 118.4 (5) | O21A—Cl9A—O22A | 96.4 (14) |
C16—C11—C2 | 120.4 (5) | O23A—Cl9A—O22A | 79.0 (12) |
C12—C11—C2 | 121.2 (5) | O20A—Cl9A—O22A | 115.5 (15) |
C13—C12—C11 | 121.4 (6) | Cl9A—O22A—O23A | 49.8 (7) |
C13—C12—H12 | 119.3 | Cl9A—O23A—O22A | 51.3 (8) |
| | | |
C10—O1—C2—C3 | 2.0 (7) | C4—C9—C10—C8 | −178.8 (5) |
C10—O1—C2—C11 | 179.7 (4) | C5—C9—C10—C8 | −0.2 (7) |
O1—C2—C3—C4 | −1.7 (8) | O1—C2—C11—C16 | −179.3 (4) |
C11—C2—C3—C4 | −179.1 (5) | C3—C2—C11—C16 | −1.8 (8) |
C2—C3—C4—C9 | 0.8 (8) | O1—C2—C11—C12 | 0.0 (7) |
C2—C3—C4—C18 | −179.6 (5) | C3—C2—C11—C12 | 177.5 (5) |
C9—C5—C6—C7 | −0.1 (10) | C16—C11—C12—C13 | −0.8 (9) |
C5—C6—C7—C8 | 0.3 (10) | C2—C11—C12—C13 | 179.9 (6) |
C6—C7—C8—C10 | −0.5 (9) | C11—C12—C13—C14 | −1.6 (10) |
C3—C4—C9—C10 | −0.2 (7) | C12—C13—C14—C15 | 3.1 (9) |
C18—C4—C9—C10 | −179.7 (5) | C12—C13—C14—Cl17 | −178.6 (5) |
C3—C4—C9—C5 | −178.6 (5) | C13—C14—C15—C16 | −2.2 (9) |
C18—C4—C9—C5 | 1.8 (9) | Cl17—C14—C15—C16 | 179.5 (4) |
C6—C5—C9—C10 | 0.1 (8) | C14—C15—C16—C11 | −0.3 (8) |
C6—C5—C9—C4 | 178.5 (5) | C12—C11—C16—C15 | 1.7 (8) |
C2—O1—C10—C8 | 177.9 (4) | C2—C11—C16—C15 | −179.0 (5) |
C2—O1—C10—C9 | −1.4 (7) | O21A—Cl9A—O22A—O23A | −164.2 (17) |
C7—C8—C10—O1 | −178.9 (5) | O20A—Cl9A—O22A—O23A | 94.6 (15) |
C7—C8—C10—C9 | 0.4 (8) | O21A—Cl9A—O23A—O22A | 75 (7) |
C4—C9—C10—O1 | 0.5 (7) | O20A—Cl9A—O23A—O22A | −114.4 (15) |
C5—C9—C10—O1 | 179.1 (4) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C6—H6···O20i | 0.93 | 2.60 | 3.476 (17) | 156 |
C13—H13···O21ii | 0.93 | 2.50 | 3.213 (16) | 133 |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, −y+1, −z. |
Experimental details
| (Ia) | (Ib) |
Crystal data |
Chemical formula | C16H12ClO+·ClO4− | C16H12ClO+·ClO4− |
Mr | 355.16 | 355.16 |
Crystal system, space group | Monoclinic, P21/n | Monoclinic, P21/c |
Temperature (K) | 290 | 290 |
a, b, c (Å) | 11.0290 (19), 12.817 (2), 11.2083 (18) | 8.0631 (15), 11.873 (3), 16.487 (2) |
β (°) | 90.173 (13) | 93.292 (14) |
V (Å3) | 1584.4 (4) | 1575.8 (5) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.43 | 0.43 |
Crystal size (mm) | 0.3 × 0.3 × 0.2 | 0.5 × 0.4 × 0.3 |
|
Data collection |
Diffractometer | Siemens P3/PC diffractometer | Siemens P3/PC diffractometer |
Absorption correction | – | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2915, 2763, 2124 | 2957, 2748, 1814 |
Rint | 0.025 | 0.036 |
(sin θ/λ)max (Å−1) | 0.595 | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.126, 0.92 | 0.049, 0.123, 0.85 |
No. of reflections | 2763 | 2748 |
No. of parameters | 208 | 255 |
No. of restraints | 0 | 261 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.32, −0.22 | 0.20, −0.26 |
Selected geometric parameters (Å, º) for (Ia) topO1—C2 | 1.326 (2) | C2—C11 | 1.448 (3) |
O1—C10 | 1.366 (2) | C14—Cl17 | 1.733 (2) |
| | | |
O1—C2—C3 | 119.13 (18) | C2—O1—C10 | 122.21 (15) |
O1—C2—C11 | 113.14 (15) | | |
| | | |
O1—C2—C3—C4 | 1.7 (3) | C3—C2—C11—C12 | 175.5 (2) |
C2—O1—C10—C9 | 0.6 (3) | C12—C13—C14—Cl17 | −177.48 (18) |
Hydrogen-bond geometry (Å, º) for (Ia) top
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O22 | 0.93 | 2.52 | 3.377 (5) | 154 |
Cl—O···π interactions (Å,°) in (Ia) topX | I | J | I···J | X···J | X-I···J |
Cl19 | O20 | Cg1i | 3.134 (3) | 3.684 (2) | 101.9 (2) |
Cl19 | O22 | Cg1i | 3.382 (4) | 3.684 (2) | 91.7 (2) |
Cl19 | O22 | Cg2i | 3.427 (4) | 4.409 (2) | 128.5 (2) |
Cl19 | O23 | Cg1i | 3.834 (3) | 3.684 (2) | 73.4 (2) |
Symmetry code: (i) 1/2 − x,y − 1/2,3/2 − z.
Cg1 is the centroid of the ring O1/C2–C4/C9/C10 and Cg2 is the centroid of the ring C5–C8/C10/C9. |
π–π interactions (Å,°) in (Ia) topCgI | CgJ | Cg···Cg | Dihedral angle | Interplanar distance | Offset |
1 | 3ii | 3.610 (2) | 5.2 | 3.479 (3) | 0.964 (2) |
3 | 1ii | 3.610 (2) | 5.2 | 3.510 (3) | 0.844 (2) |
Symmetry code: (ii) −x, 1 − y, 2 − z.
Notes: Cg1 is the centroid of the ring O1/C2–C4/C9/C10 and Cg3 is the centroid of the ring C11–C16. Cg···Cg is the distance between ring centroids. The dihedral angle is that between the planes of the rings CgI and CgJ. The interplanar distance is the perpendicular distance of CgI from ring J. The offset is the perpendicular distance of ring I from ring J. |
Selected geometric parameters (Å, º) for (Ib) topO1—C2 | 1.323 (6) | C2—C11 | 1.455 (7) |
O1—C10 | 1.376 (6) | C14—Cl17 | 1.757 (5) |
| | | |
O1—C2—C3 | 119.7 (5) | C2—O1—C10 | 121.6 (4) |
O1—C2—C11 | 114.4 (4) | | |
| | | |
O1—C2—C3—C4 | −1.7 (8) | C3—C2—C11—C12 | 177.5 (5) |
C2—O1—C10—C9 | −1.4 (7) | C12—C13—C14—Cl17 | −178.6 (5) |
Hydrogen-bond geometry (Å, º) for (Ib) top
D—H···A | D—H | H···A | D···A | D—H···A |
C6—H6···O20i | 0.93 | 2.60 | 3.476 (17) | 156 |
C13—H13···O21ii | 0.93 | 2.50 | 3.213 (16) | 133 |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, −y+1, −z. |
C—Cl···π and Cl—O···π interactions (Å,°) in (Ib) topX | I | J | I···J | X···J | X-I···J |
C14 | Cl17 | Cg1iii | 3.941 (2) | 4.290 (5) | 89.1 (2) |
Cl19 | O22 | Cg1 | 3.229 (18) | 3.854 (9) | 106.7 (10) |
Cl19 | O22 | Cg2 | 3.223 (17) | 4.316 (10) | 136.0 (10) |
Symmetry code: (iii) 1 − x, −y, −z.
Cg1 is the centroid of the ring O1/C2–C4/C9/C10 and Cg2 is the centroid of the ring C5–C8/C10/C9. |
π–π interactions (Å,°) in (Ib) topCgI | CgJ | Cg···Cg | Dihedral angle | Interplanar distance | Offset |
2 | 3i | 3.713 (3) | 2.2 | 3.409 (3) | 1.464 (3) |
3 | 2iv | 3.713 (3) | 2.2 | 3.464 (3) | 1.336 (3) |
3 | 3iii | 4.007 (3) | 0.0 | 3.441 (3) | 2.054 (3) |
Symmetry codes: (i) x − 1, y, z; (iii) 1 − x, −y, −z; (iv) 1 + x, y, z.
Notes: Cg2 is the centroid of the ring C5-C8/C10/C9 and Cg3 is the centroid of the ring C11-C16. Cg···Cg is the distance between ring centroids. The dihedral angle is that between the planes of the rings CgI and CgJ. The interplanar distance is the perpendicular distance of CgI from ring J. The offset is the perpendicular distance of ring I from ring J. |
2-Phenylchromenium salt-type systems occur in natural dyes (anthocyanides), exhibiting a distinctive biological significance (Gera, 1982). Owing to their strong absorption in the orange–red spectroscopic region, they are used as dyes, for example in the food industry (Timberlake & Bridle, 1980). Some 2-phenylchromenium salts exhibit intense luminescence and are used as lasing materials (Maeda, 1984; Deligeorgiev et al., 1987). Our investigations of the features of 2-phenylchromenium cations and their dimers and nucleophilic complexes (Roshal et al., 1998; Roshal et al., 2002) have shown that the spectroscopic properties of these species depend on their structure, mainly the angle between the chromenium and phenyl fragments (Roshal, 1999). The opportunity to investigate the influence of structure on spectroscopic features arose when we found two polymorphs of different colours following the crystallization of 2-(4-chlorophenyl)-4-methylchromenium perchlorate from ethyl acetate, subsequently designated (Ia) and (Ib). There is, to our knowledge, only one report in the Cambridge Structural Database (Version?; Allen, 2002) concerning 2-phenylchromenium derivatives (Busetta et al., 1974). The present work thus extends our knowledge of the crystal structures of this important group of compounds.
The parameters characterizing the geometry of the aromatic skeleton in both polymorphs are given in Tables 1 and 5. The relevant bond lengths, as well as the valence and dihedral angles, are comparable, except the C3—C2—C11—C12 angle, which differs by 2.0 (5)°. The angles between the mean planes of rings 1 (defined by atoms O1/C2–C4/C9/C10) and 2 (defined by atoms C5–C8/C9/C10) are 0.0 (2)° in polymorph (Ia) and 1.5 (5)° in polymorph (Ib). Furthermore, the angles between the mean planes of the chromenium skeleton (defined by atoms O1/C2–C10) and ring 3 (defined by atoms C11–C16) are 5.2 (2)° in polymorph (Ia) and 1.6 (5)° in polymorph (Ib). This implies that all three rings lie almost in one plane in both polymorphs.
In polymorph (Ia) (Fig. 1), the cations and the anions form ion pairs via Cl—O···π interactions (Fig. 2, Table 3). Adjacent ion pairs, related by a centre of symmetry, are linked via π–π interactions between cationic fragments (involving rings 1 and 3) (Table 4), and the resulting dimers are linked through a network of C—H···O(perchlorate) interactions (Table 2) between the cationic and anionic fragments of neighbouring ion pairs (Fig. 2). The angle between the mean planes defined by the whole aromatic skeleton [defined by atoms O1/C2–C16] is either 0°, in the case of the cationic fragments involved in dimers, or 32.6 (2)°, if we take into account the cationic fragments of adjacent ion pairs not constituting dimers.
The tetrahedral perchlorate anions in polymorph (Ib) occupy two positions, with occupancy factors of 0.557 (11) and 0.443 (11) for Cl19/O20–O23 and Cl9A/O20A–O23A, respectively (Fig. 3). Disordered perchlorate anions have been reported by others (e.g. Sun, 2006; Athimoolam & Rajaram, 2006), which suggests that disorder is not a feature unique to this entity. The cations and anions form ion pairs via Cl—O···π interactions (Figs. 4 and 5, Table 7). The ion pairs are arranged in columns extending along the a axis, in which the aromatic skeletons are parallel to one another (Fig. 4) and inclined at an angle of 63.6 (5)° relative to the bc plane. Cations of neighbouring ion pairs in columns are linked via π–π interactions, whereas cations and anions do so via C—H···O (perchlorate) interactions (Fig. 4, Tables 6 and 8). Adjacent columns are linked via C—Cl···π and π–π interactions between cations (Fig. 5, Tables 7 and 8), forming pairs of columns. Within a pair of columns, the aromatic skeletons are parallel. In adjacent pairs of columns, linked through C—H···O(perchlorate) interactions (Fig. 5, Table 6) and O···Cl contacts [Cl17···O23 = 3.26 (1) Å (symmetry code: 1 − x, y − 1/2, 1/2 − z); Fig. 4], the aromatic skeletons are at an angle of 66.1 (2)° [the angle between the mean planes defined by all the atoms of the aromatic skeletons of non-interacting cations], which produces a herringbone pattern.
The crystal structures of both polymorphs are stabilized by a network of the above-mentioned short-range interactions, as well as by long-range electrostatic interactions between ions.
All interactions demonstrated were found by PLATON (Spek, 2003). The C—H···O interactions exhibit a hydrogen-bond type nature (Steiner, 1999). Interactions between the perchlorate anion or electronegative Cl atom at ring 3, and rings 1 and 2, respectively identified as Cl—O···π and C—Cl···π interactions, should be of an attractive nature, since the chromenium system is positively charged (Dorn et al., 2005). An attractive nature should also be exhibited by the [Original meaning not clear - please check rephrasing] C—Cl···O(perchlorate) interactions (Allen et al., 1997) identified as O···Cl contacts.
To obtain some idea of how the chromenium (1 and 2) and phenyl (3) rings are mutually oriented in an isolated cation, we optimized its structure at the DFT(B 3LYP)/6–31 G** level (GAUSSIAN98; Frisch et al., 1998) and calculated the angle between the mean planes of these fragments. The value obtained was 0.3°, which means that the whole aromatic system is planar. Distortion from planarity of the aromatic system in both polymorphs, apparent in the crystallographic data, may be the cause of their different spectroscopic behaviour.
Having optimized the structure of the cation, we calculated relative partial charges using a natural bond order (NBO) analysis (Reed et al., 1988), a Mulliken population analysis (Mulliken, 1955a,b) and the electrostatic potential (ESP) fit method (Besler et al., 1990). It is commonly believed that electron deficiency occurs at the ring O atom, but our calculations revealed the reverse situation: there was an excess negative charge at this atom [−0.416 (NBO), −0.488 (Mulliken) and −0.278 (EPS)]. It seems, therefore, that, in this case, traditional assumptions may have to be revised.