Crystal Inclusion Formation of a New Type of Dumbbell-Shaped Host Compound Featuring Two Bulky 2,3,4,5-Tetraphenylcyclopenta-2,4-dien-1-ol Terminal Groups Attached to a Linear Spacer Unit

Article

pubs.acs.org/crystal

Crystal Inclusion Formation of a New Type of Dumbbell-Shaped

Host Compound Featuring Two Bulky 2,3,4,5-Tetraphenylcyclopenta-

2,4-dien-1-ol Terminal Groups Attached to a Linear Spacer Unit

Alexander Ruﬀani, Wilhelm Seichter, Anke Schwarzer, and Edwin Weber*

Institut fur Organische Chemie, Technische Universitat Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg, Sachsen,

̈

Germany

S

* Supporting Information

ABSTRACT: Four new host compounds of dumbbell shape featuring bulky

2,3,4,5-tetraphenylcyclopenta-2,4-dien-1-ol moieties attached to both ends of

a linear spacer element of diﬀerent lengths comprising both 1,4-phenylene

and ethynylene subunits are synthesized and corresponding crystal inclusions

involving DMSO, DMF, MeCN, and THF as guest solvents (seven examples

of inclusion compounds) are isolated. X-ray structural analysis shows the

formation of 1:2 host/guest entities being a basic supramolecular motif

of the crystal inclusions. Nevertheless, additional solvent molecules seem to

be necessary for stabilization of the crystal structure in most cases of the

inclusion species indicating the occurrence of unusually high stoichiometric

ratios of included solvent as a speciﬁc characteristic of the new type of host

molecule.

related, host compounds^18,19containing the same bulky 2,3,4,5-

INTRODUCTION

■

tetraphenylcyclopenta-2,4-dien-1-ol moiety, but as a monofunc-

tional species showing a more simple molecular constitution,

are worth mentioning at this point and will be regarded in the

discussion.

The crystal engineering of solid-state materials is of ever-

increasing interest to chemists and materials scientist alike.¹⁻⁴

Selective formation of crystal inclusion compounds is one of

the main challenges in this area of research.⁵⁻⁷This has given

rise to the design of a variety of host compounds, all being

intended to entrap molecular guests in their crystal lattice.^8,9

A guiding principle which has proven very successful in this

respect involves the presence of a rather bulky and rigid

molecular construction, in order to prevent close packing, and

also inside located polar, mainly hydrogen donor/acceptor

groups, allowing for speciﬁc guest interaction.¹⁰This concept is

commonly referred to as the “coordinato-clathrate” approach.¹¹

Representative examples of host structures developed from this

line of thought correspond to wheel-and-axle,^12,13scissor-like,¹⁴

roof-shaped,¹¹or dumbbell type¹⁵⁻¹⁷molecular geometries.

The host compounds presented in this paper belong to the

latter subclass of compounds, i.e., the dumbbell type, but are

new in their respective constitutions. In particular, they contain

a 2,3,4,5-tetraphenylcyclopenta-2,4-dien-1-ol moiety, which is

an especially bulky group, attached to the ends of a linear

spacer element diﬀering in length. As a result of this speciﬁc

structural feature, crystal inclusion compounds are formed that

attract attention due to the remarkably high content of guest

solvent, in some cases besides some other structural character-

istics, reported in this paper. In a more detailed speciﬁcation,

we describe the synthesis of the dumbbell-shaped host

compounds 1−4, including seven examples of corresponding

solvent inclusions (Scheme 1) and discuss the X-ray crystal

structures of the inclusion complexes. A few known, in a way

RESULTS AND DISCUSSION

■

Host Synthesis. The host compounds 1−4 (Scheme 1) were

synthesized from tetracyclone and the respective organyldilithium

compound, the latter being prepared from the respective

aryl dibromide (1,4-dibromobenzene, 4,4′-dibromobiphenyl, 4,4′-

dibromotolane) or 1,4-diethynylbenzene and n-BuLi, following

a method described for the preparation of 1 and 2.²⁰The

tetracyclone was obtained from benzil and 1,3-diphenylpropan-

2-one according to the established procedure.²¹4,4′-Dibromo-

tolane was synthesized from bibenzyl via a bromination and

elimination route,^22,23while 1,4-dibromobenzene is commercially

available. 1,4-Diethynylbenzene was prepared by Pd-catalyzed

cross-coupling reaction²⁴of 1,4-dibromobenzene with

2-methylbut-3-yn-2-ol,²⁵and subsequent cleavage of the block-

ing group.²⁶Because of the high aﬃnity of the host com-

pounds to retain solvent molecules, attainment of satisfactory

elemental analyses caused diﬃculties. Moreover, in the ¹³C

NMR spectrum of compound 3, the carbon signal for the

symmetric acetylene group is not clearly perceptible. However,

Received: March 9, 2016

Revised: April 28, 2016

A

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

In the inclusion structures formed of 1−4, the phenyl rings

within the pentacyclic end groups of the host molecules exhibit

a propeller-like arrangement around the cyclopentadiene ring

which reduces intramolecular sterical strain. Consequently,

restricted conformational freedom is found within these units as

deducible from the geometric parameters listed in Table 2. The

conformational features of the diol hosts may be described best

by calculation of interplanar angles which deﬁne the inclination

of the phenyl rings with respect to the plane of the cyclo-

pentadiene ring to which they are attached. In order to simplify

the characterization of the crystal structures, the ring fragments

of the molecules are marked by capital letters in Scheme 1 and

in the ﬁgures showing the molecular structures.

Scheme 1. Chemical Formula Structures Including Ring

Speciﬁcation of the Studied Host Molecules 1−4 and

Speciﬁcation of Corresponding Inclusion Compounds

Crystallization of 1 from dimethyl sulfoxide yields colorless

plates of 1a crystallizing in the orthorhombic space group Pna2₁

with the asymmetric part of the unit cell containing one host

molecule and three molecules of solvent (Figure 1a). Taking

into account experimental error, the double bonds within the

cyclopentadiene rings have identical bond lengths [1.350(3)−

1.353(3) Å]. Because of conjugation eﬀects, the C(sp²)−

C(sp²) single bonds within these rings are signiﬁcantly shorter

[1.497(3), 1.499(3) Å] than the C(sp²)−C(sp³) single bonds

[1.510(3)−1.536(3) Å]. The lengths of C(sp²)−C(arene)

single bonds range between 1.474(4) and 1.490(3) Å, C(sp³)−

C(arene) bonds are 1.536(3) [1.539(3) Å]. These values are

comparable to those found in the crystal structure of 1,2,3,4,5-

pentaphenylcyclopenta-2,4-dien-1-ol,¹⁸which represents the basic

building unit of the diol hosts discussed in this paper. The central

aromatic ring F is oriented nearly orthogonal with respect to

the cyclopentadiene rings [87.8(1), 89.7(1)°]. According to their

distinctive acceptor character two of the guest molecules are

linked to the host via conventional hydrogen bonds, whereas an

only weak C−H···O contact²⁷is formed by the third highly

disordered guest molecule. The crystal packing of 1a (Figure 2a)

reveals layers of host and guest molecules being stacked in

alternating order in direction of the crystallographic c-axis. The

aromatic nature of the host molecules give rise to extensive

intermolecular association via C−H···π arene hydrogen bonds.²⁸

It should be mentioned that in this type of interactions individual

carbon atoms of aromatic rings instead of commonly used ring

centroids were chosen as acceptor positions to obtain well-

deﬁned hydrogen bond geometries (see Table 3). The H···C

distances of these contacts range between 2.69 and 2.87 Å, which

is shorter than the sum of the van der Waals radii of carbon and

hydrogen (2.90 Å). Within a given layer of guest molecules, the

molecular dipoles are aligned along the a-axis.

the Raman spectrum for this compound indicated a deﬁnite

band for the carbon triple bond at 2220 cm⁻¹.

X-ray Structural Study of Inclusion Compounds. The

hosts 1−4 yielded crystalline inclusion compounds with a

selection of mainly polar guest solvents. They involve DMSO

and DMF, both being of strong polar aprotic nature, and as

exceptions of this particular solvent class acetonitrile and THF

being aprotic solvents of weaker polarity, giving rise to a variety

of corresponding crystalline inclusions (1a, 1b, 2a−2c, 3a, and

4a) speciﬁed in Scheme 1. Not only because of the unusual

host/guest stoichiometry showing a remarkably high guest

ratio from 1:3 to 1:6, in some of the cases, considering the

bifunctionality of the host molecules, but also because of the

newness of the host constitutions in general, crystal structures

of the present inclusion compounds are to be expected to

oﬀer interesting insight into the inclusion behavior of these

speciﬁc host molecules. However, it should already be noted

at this point that 4a (4·DMSO, 1:5) raised diﬃculties to

obtain perfect crystals for X-ray diﬀraction. For all inclusion

compounds, crystallographic data and reﬁnement parameters

are presented in Table 1, while geometric parameters and

information regarding hydrogen bonding in the crystals are

summarized in Tables 2 and 3, respectively. Perspective views

of the molecular structures including selected atom number-

ing and speciﬁcation of ring units are shown in Figure 1

(a complete numbering system of atoms is given in Figure S1).

Illustrations of the packing structures inclusive of excerpts of

relevant interaction modes are displayed in Figure 2, Figure 3,

Figure 4, Figure 5, and Figure 6 oﬀering properties as stated in

the following.

Similar structural features are also found in the inclusion

compound of 1 with dimethylformamide (1:4) 1b, although

the host−guest stoichiometric ratio diﬀers from that of 1a. The

asymmetric entity of the unit cell (space group P1) contains

̅

one-half of the diol host and two guest molecules; i.e., the

host molecule adopts inversion symmetry which implies an

anti-conﬁguration of its hydroxy groups. An ORTEP diagram

of the molecular structure is depicted in Figure 1b. As can be

seen from the structure motif in Figure 3, one fraction of guest

molecules forms the expected O−H···O hydrogen bonds to

the host, whereas the remaining guest molecules are involved

in relatively short C−H_arene···O contacts. Moreover, C−H···O

hydrogen bond interactions connect the guest molecules to one

another. According to the given mode of hydrogen bonding,

host and guest molecules are connected to supramolecular layers

extending parallel to the crystallographic ac plane. At ﬁrst sight,

the packing of molecules in 1a (Figure 2a) and of the present

B

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

C

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Table 2. Selected Conformational Parameters and Bond Lengths in the Crystal Structures of 1a,b, 2a−c, 3a, and 4a

compound

1a

1b

2a

2b

2c

3a

4a

Dihedral Angles (deg)

34.6(1)

mpla(A)/mpla(E)

mpla(B)/mpla(E)

mpla(C)/mpla(E)

mpla(D)/mpla(E)

mpla(E)/mpla(F)

mpla(A′)/(E′)

mpla(B′)/(E′)

mpla(C′)/(E′)

mpla(D′)/(E′)

mpla(E′)/(F)

51.4(1)

40.0(1)

44.4(1)

81.5(1)

87.8(1)

39.4(1)

50.0(1)

40.5(1)

69.5(1)

89.7(1)

42.9(1)

50.9(1)

37.1(1)

54.7(1)

85.3(1)

51.6(1)

47.6(1)

56.0(1)

47.0(1)

84.7(1)

79.7(1)

57.1(2)

47.6(1)

45.8(1)

89.9(1)

10.7(2)

36.1(1)

41.5(1)

58.9(1)

57.6(1)

87.4(1)

40.8(1)

46.6(1)

59.8(1)

64.5(1)

80.6(1)

18.2(1)

33.1(2)

51.7(1)

51.9(1)

60.6(1)

89.6(1)

32.7(2)

55.4(1)

59.2(1)

35.4(1)

47.6(4)

57.1(1)

52.7(3)

47.6(3)

55.1(3)

86.4(3)

32.0(5)

55.2(3)

48.8(3)

75.9(3)

83.4(3)

54.2(1)

55.6(1)

87.3(1)

mpla(F)/(F′)

mpla(E′)/(F′)

16.8(1)

86.3(1)

Torsion Angles (deg)

C(30)−C(1)−O(1)−H(1)

C(33)−C(36)−O(2)−H(2)

C(39)−C(1)−O(1)−H(1)

C(39)−C(40)−O(2)−H(2)

C(39)−C(42)−O(2)−H(2)

C(41)−C(44)−O(2)−H(2)

bond lengths (Å)

C(1)−C(2)

C(2)−C(3)

C(3)−C(4)

C(4)−C(5)

C(1)−C(5)

−170.5(1)

171.6(1)

69.9(1)

−175.0(1)

−172.8(1)

−173.1(1)

42.5(5)

−176.0(1)

−39.5(5)

171.6(1)

175.9(1)

91.0(1)

1.510(3)

1.530(3)

1.531(3)

1.352(4)

1.499(4)

1.353(4)

1.526(4)

1.520(4)

1.527(5)

1.540(2)

1.524(5)

1.543(12)

1.353(3)

1.499(3)

1.352(3)

1.527(4)

1.536(3)

1.354(3)

1.509(3)

1.344(3)

1.538(3)

1.529(3)

1.345(5)

1.497(5)

1.347(5)

1.530(5)

1.528(5)

1.350(2)

1.498(2)

1.340(2)

1.530(2)

1.362(5)

1.493(5)

1.345(5)

1.546(5)

1.529(5)

1.442(6)

1.337(12)

1.508(11)

1.336(12)

1.559(12)

1.498(12)

C(1)−C(30)

C(33)−C(36)

C(36)−C(37)

C(37)−C(38)

C(38)−C(39)

C(39)−C(40)

C(36)−C(40)

C(33)−C(36)

1.524(3)

1.351(3)

1.497(4)

1.350(3)

1.536(4)

1.539(3)

1.439(6)

1.485(11)

C(41)−C(44)

1.542(5)

C(42)−C(43)

C(43)−C(44)

C(44)−C(45)

C(45)−C(46)

1.531(5)

1.350(5)

1.494(5)

1.345(5)

1.533(2)

1.342(2)

1.495(2)

1.349(2)

1.529(5)

1.359(5)

1.484(5)

1.348(5)

1.524(5)

C(46)−C(47)

C(47)−C(48)

C(48)−C(44)

C(42)−C(46)

C(39)−C(42)

1.532(5)

1.522(5)

1.539(2)

1.530(2)

structure (Figure 2b) appear similar, showing layers of host

and guest molecules being stacked in an alternating order. The

occurrence of diﬀerent space group symmetries, however, implies

structural diﬀerences. While in the crystal structure of 1a, the

orientation of host molecules of consecutive layers are related

by the 2-fold screw axis; in the structure of 1b the inversion

symmetry of the host molecule results in a unique orientation of

the molecules.

Crystals of the diol 2 obtained from CH₃CN turned out to

be an inclusion compound (2a) of the host/guest ratio of

1:1 with the guest molecule CH₃CN disordered around the

symmetry center. This means that only one OH group of

the host molecule acts as a donor for hydrogen bonding. The

stoichiometric unit of 2a is displayed in Figure 1c. The central

phenyl rings of the host are not perfectly planar giving rise to

the molecule to adopt a slight S-shaped bend along its biphenyl

spacer moiety. The packing diagram of 2a (Figure 4a) reveals

that the crystal is composed of 1:1 host−guest complexes

being linked via C−H···O bonding to inﬁnite chains extending

parallel to the crystallographic c-axis. Interconnection between

supramolecular chains is realized by C−H···π-interactions

between the aromatic rings.

The inclusion compound of 2 with dimethylformamide (1:3)

(2b) crystallizes in the orthorhombic space group Pna2₁(Z = 4);

i.e. the host molecule lacks a center of inversion. The twist angle

between the rings of the central biphenyl unit is 10.7(2)°.

As expected, two of the guest molecules contribute to forma-

tion of 1:2 host−guest units via O−H···O hydrogen bonding

(Figure 1d). The remaining solvent molecule is involved in

guest−guest association with its oxygen atom acting as a

bifurcated acceptor. In the crystal lattice, the host molecules are

packed in such a manner as to leave channels running along the

D

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Table 3. Selected Noncovalent Interactions in the Inclusion Structures of 1a,b, 2a−c, 3a, and 4a

atoms involved D−H···A

1a

symmetry

distance D···A

H···A

angle, D−H···A

O(1)−H(1)···O(1F)

O(2)−H(2)···O(1G)

C(29)−H(29)···O(1F)

C(64)−H(64)···O(1G)

C(1F)−H(1F3)···O(2)

C(57)−H(57)···O(1H)

−x, 1−y, 0.5+z

1+x, y, 1+z

2.867(3)

2.773(3)

3.527(3)

3.562(4)

3.380(4)

3.613(4)

3.709(4)

3.529(4)

3.714(4)

3.678(4)

2.04

1.94

2.67

2.69

2.66

2.72

2.77

2.70

2.81

2.80

167.7

173.1

150.4

153.2

130.3

157.1

168.1

145.5

159.7

157.9

1−x, 1−y, 0.5+z

1+x, y, 1+z

−0.5+x, 1.5−y, −1+z

1+x, −1+y, 1+z

0.5+x, 1.5−y, z

−0.5+x, 1.5-y, z

−0.5+x, 0.5−y, z

2−x, 1−y, −0.5+z

a

C(48)−H(48)···C(20)

C(20)−H(20)···C(42)

C(13)−H(13)···C(55)

a

C(28)−H(28)···C(57)

1b

O(1)−H(1)···O(1G)

C(7)−H(7)···O(1)

C(3H)−H(3H3)···O(1G)

C(14)−H(14)···O(1H)

C(3G)−H(3G1)···O(1)

C(2G)−H(2G3)···O(1H)

x, y, z

2.746(3)

3.109(4)

3.482(5)

3.195(3)

3.667(3)

3.440(5)

3.758(4)

1.91

2.46

2.61

2.48

2.69

2.52

2.85

171.0

125.5

148.7

131.6

175.7

156.4

160.4

x, y, z

1+x, y, z

1−x, 2−y, 1−z

−x, 2−y,1−z

x, y, z

a

C(8)−H(8)···C(27)

x, 1+y, z

2a

O(1)−H(1)···N(1A)

C(13)−H(13)···O(1)

C(7)−H(7)···O(1)

x, −1+y, z

1−x, −y, 1−z

x, y, z

3.055(5)

3.438(6)

3.080(6)

3.699(6)

3.697(6)

2.25

2.52

2.41

2.80

2.81

160.4

161.4

127.3

158.8

156.8

a

C(17)−H(17)···C(9)

1.5−x, 0.5+y, 1.5−z

1−x, 1−y, 1−z

a

C(2)−H(21)···C(15)

2b

O(1)−H(1)···O(1H)

O(2)−H(2)···O(1F)

C(2H)−H(2H1)···O(1G)

C(2F)−H(2F1)···O(1G)

C(3H)−H(3H3)···O(2)

x, y, z

2.623(4)

2.686(4)

3.477(10)

3.453(7)

3.408(8)

3.614(8)

3.640(7)

3.725(8)

3.539(8)

3.623(7)

1.81

1.85

2.61

2.68

2.67

2.76

2.80

2.79

2.72

2.83

161.7

176.3

147.1

136.4

132.3

146.8

147.5

167.7

144.2

141.8

−1+x, y, z

0.5+x, 0.5−y, z

1−x, 1−y, 0.5+z

0.5−x, −0.5+y, −0.5+z

x, −1+y, z

0.5+x, 2.5−y, z

x, 1+y, z

a

C(2G)−H(2G3)···C(11)

a

C(8)−H(8)···C(64)

a

C(10)−H(10)···C(21)

C(41)−H(41)···C(10)

C(69)−H(69)···C(13)

a

−0.5+x, 2.5−y, z

−0.5+x, 1.5−y, z

a

2c

O(1)−H(1)···O(1H)

O(2)−H(2)···O(1F)

C(11)−H(11)···O(1)

C(52)−H(52)···O(2)

C(49)−H(49)···O(1G)

C(56)−H(56)···O(1J)

C(57)−H(57)···O(1I)

C(16)−H(16)···O(1K)

−x, 2−y, 1−z

1−x, 1−y, −z

x, y, z

2.774(2)

2.787(2)

3.087(2)

3.140(2)

3.447(2)

3.548(3)

3.455(3)

3.545(3)

3.571(4)

3.761(4)

1.94

1.96

2.41

2.49

2.59

2.76

2.71

2.74

2.67

2.83

171.1

170.2

127.9

125.3

150.3

140.8

135.3

142.8

151.9

157.3

x, y, z

x, −1+y, z

−1+x, 1+y, z

1+x, y, z

b

C(1G)−H(1G1)···Cg(B)

C(3H)−H(3H2)···Cg(D)

3a

b

x, −1+y, z

O(1)−H(1)···O(1G)

O(2)−H(2)···O(1H)

C(1G)−H(1G3)···O(1H)

C(7)−H(7)···O(1)

C(8)−H(8)···O(1G)

C(72)−H(72)···O(2)

x, y, 1+z

x, y, z

2.820(4)

2.717(4)

3.332(5)

3.054(5)

3.329(5)

2.981(5)

3.508(5)

3.723(5)

3.448(5)

3.633(5)

1.98

2.01

2.41

2.38

2.51

2.31

2.62

2.84

2.65

2.70

173.3

141.4

156.7

128.0

144.8

126.8

156.0

155.1

142.2

159.7

1+x, y, z

x, y, z

2−x, 1−y, 1−z

x, y, z

b

C(28)−H(28)···Cg(B)

C(53)−H(53)···Cg(D)

C(66)−H(66)···C(52)

−1+x, y, z

x, y, −1+z

−1+x, y, z

x, y, −1+z

b

a

C(1G)−H(1G1)···C(13)

4a

O(1)−H(1)···O(1C)

O(2)−H(2)···O(1B)

−x, 1−y, 1−z

x, y, z

2.701(13)

2.690(10)

1.91

1.88

154.9

162.9

E

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Table 3. continued

Article

atoms involved D−H···A

symmetry

1+x, −1+y, z

x, y, −1+z

−1+x, y, z

x, y, 1+z

distance D···A

H···A

angle, D−H···A

C(1A)−H(1A1)···O(1)

C(1A)−H(1A3)···O(1D)

C(2B)−H(2B2)···O(1E)

C(1C)−H(1C2)···O(1A)

C(1C)−H(1C3)···O(1B)

C(2C)−H(2C2)···O(1A)

C(29)−H(29)···O(1)

C(1E)−H(1E3)···O(2)

C(34)−H(34)···O(1E)

C(66)−H(66)···O(1D)

3.319(18)

3.160(18)

3.377(18)

3.420(20)

3.477(18)

3.252(20)

3.053(14)

3.381(20)

3.128(12)

3.211(20)

2.51

2.25

2.52

2.60

2.59

2.37

2.51

2.50

2.34

2.49

140.5

156.5

142.7

142.4

151.5

145.8

116.3

152.1

139.5

132.8

x, y, 1+z

x, y, z

1−x, 1−y, −z

−1+x, y, −1+z

a

To obtain a reasonable hydrogen bond geometry, an individual atom of an aromatic ring instead of the ring center was chosen as an acceptor.

Cg means the center of an aromatic ring. 2c, 3a: Ring B: C(6)···C(11) ; ring D: C(18)···C(23).

b

crystallographic a-axis with the hydroxy groups sticking out of

a three-dimensional network. Pairs of guest molecules reside

in closed lattice voids created by aromatic rings of six host

molecules.

the hydrophobic channel walls. Within a given channel, the guest

molecules form inﬁnite C−H···O bonded strands with a unique

alignment of their dipoles (Figure 4b). Compared with 1b, the

elongation of the host axis by an additional phenyl group

markedly inﬂuences the mode of host−host interaction leading

to formation of multiple C−H···π arene contacts [d(H···π)

2.72−2.83 Å].

Replacement of a highly coordinating dipolar aprotic guest

solvent (DMF) by a less polar guest species has a fundamental

inﬂuence on the host lattice structure which is evident from the

inclusion compound of 2 with tetrahydrofuran 2c versus 2b. In

As already indicated at the beginning, multiple attempts of

growing crystals of 4 from DMSO permanently gave only

crystals (4a) of poor quality leading to a data set of low

resolution (θ_max≈ 22.0°). Nevertheless, we succeeded to solve

the crystal structure which, however, could not be reﬁned to an

acceptable level. This is evident from a high R-value. The number

of observed reﬂections represents less than 50% of the number

of unique reﬂections. Taking into account the conditions, the

crystals were found to belong to the space group P1 with the

̅

asymmetric part of the unit cell comprising one host molecule

and ﬁve molecules of DMSO, two of them disordered over

two positions. A perspective view of the molecular structure is

displayed in Figure 1g. Because of packing forces, the

1,4-diethynylphenylene spacer of the host molecule slightly

deviates from linearity. The aromatic ring of this unit is inclined

at angles of 83.0(2) and 86.1(2)^owith respect to the planes of

the cyclopentadiene rings. The 3D architecture of this inclusion

compound exhibits similarities with 1a and 1b, showing a layered

arrangement of host and guest molecules. An excerpt of the

packing structure of 4a is shown in Figure 6a. The high extent of

crystal solvent induces the formation of diﬀerent supramolecular

entities. As displayed in Figure 6b, one of the host hydroxyl

groups and two of the solvent molecules contribute to the forma-

tion of inﬁnite double strand-like supramolecular aggregates

comprising host−guest O−H···O and C−H···O as well as

guest−guest C−H···O interactions. The pattern of hydrogen

bonding within a strand can be regarded as being composed

of fused cyclic synthons²following the graph sets R₆⁴(16) and

R₄⁴(18).²⁹The second host hydroxyl group and the remaining

solvent molecules are connected via hydrogen bonds of the

O−H···O and C−H···O type to give a cyclic structure aggregate

(Figure 6c). The central supramolecular motif of this unit is

represented by the graph set R₆⁶(20).

the crystal structure of 2c (space group P1), the content of the

̅

asymmetric part of the unit cell, which is shown in Figure 1e,

has the very unusual host/guest stoichiometric ratio of 1:6.

Two of the guest molecules are linked in the expected way to

the host molecule by conventional O−H···O hydrogen bonds,

while the remaining guests participate in weak C−H···O contacts

to host arene hydrogens, but are not cross-linked among each

other. A view of the crystal structure along the a-axis (Figure 5a)

reveals a complex arrangement consisting of layers of guest

molecules which extend along the ab-plane and such guests

being incorporated in channel-like lattice voids of an irregular

cross-section with a maximum extension of 13.6 × 3.7 Å. Thus,

a remarkable feature of the inclusion structure is that 40.7% of

the crystal volume is occupied by solvent molecules. This high

content of crystal solvent may also explain the relatively poor

cross-linking of the host molecules.

Crystallization of 3 from DMSO yields a 1:2 solvent

inclusion compound 3a with the asymmetric part of the unit

cell containing one host molecule and two molecules of

DMSO, one of them disordered over two positions (s.o.f.

0.86, 0.14) (Figure 1f). The host molecule shows a slight bend

along the diphenylethyne spacer moiety and a dihedral angle

of 16.8(1)° with reference to the aromatic rings (F,F′). These

rings are arranged nearly orthogonal [89.6(1), 86.3(1)°] with

respect to the planes of the cyclopentadienyl rings. The overall

geometry of the host molecule basically diﬀers from those of

1 and 2, showing a syn orientation of the hydroxy groups. In the

crystal of 3a, the guest molecules are connected via O−H···O

hydrogen bonding to the host molecule leading to 1:2 complex

units as basic supramolecular entities. They are packed in such

a way that the pentacyclic moieties of the host molecules

ﬁt into the cleft left by the narrow spacer of an adjacent

molecule (Figure 5b) thus allowing a closely packed structure.

Host−host interaction is accomplished by C−H···O hydrogen

bonding and by a number of C−H···π arene contacts leading to

CONCLUSION

■

The attachment of bulky 2,3,4,5-tetraphenylcyclopenta-2,4-

dien-1-ol moieties to both ends of a linear spacer element of

diﬀerent length comprising both 1,4-phenylene and ethynylene

subunits has proven to be a structural host design for the forma-

tion of crystalline solvent inclusions. As a matter of principle,

this should be explained to the eﬀect that the high sterical

shielding of the host functional groups by the bulk of the

pentacyclic building blocks prevents self-aggregation of the host

molecules via conventional hydrogen bonding. Therefore, a

F

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 1. Molecular structures (ORTEP plots with 50% probability level) of the inclusion compounds 1a (a), 1b (b), 2a (c), 2b (d), 2c (e), 3a (f),

and 4a (g) involving numbering of relevant atoms and speciﬁcation of ring units (A−F). Complete numbering systems of atoms and ring

speciﬁcations of the host molecules are given in Figure S1. In panel c, the two disorder positions of the solvent molecule are indicated in bold and

light style.

secondary coordinating species of appropriate size (solvent

molecule) is an essential prerequisite for the formation of

an inclusion crystal corresponding with the basic idea of the

coordinato-clathrate strategy,¹¹while the general structure

of the molecules 1−4 meets the dumbbell shape construction

principle¹⁵⁻¹⁷also favoring inclusion formation. Thus, both the

G

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 2. Packing diagrams of 1a (a) and 1b (b). Oxygens are displayed as dotted, nitrogens as hatched and sulfur atoms as cross-hatched circles.

Nonrelevant hydrogen atoms have been omitted for the sake of clarity. Dashed lines represent hydrogen bond interactions.

Figure 3. Packing excerpt showing the strand formation of host and guest molecules in the structure of 1b. Dashed lines represent hydrogen bond

interactions.

hydrophobic nature of the host framework and the presence

of a polar guest species determine the three-dimensional

molecular assembly in the inclusion crystals formed of 1−4.

Being connected with this feature, it seems that the aggregation

of the host molecules is strongly driven by the formation of

an optimal number of arene−arene contacts with edge-to-face

geometry which is restricted to the accessible aromatic rings

of the end groups but leaving those of the spacer elements

uneﬀected. Moreover, with the exception of 2a, a common

feature is the formation of 1:2 host/guest units that represent

the basic supramolecular entities of the crystal structures in

parallel with the bifunctionality of the host molecules.

Nevertheless, despite these things in common, distinct

diﬀerences in the structure of the respective inclusion crystals

can be observed. While only in the case of 3a the 1:2,

respectively, in 2a the 1:1 host−guest units enable eﬀective

packing in the crystal, in all the other structures the forma-

tion of a close packing requires additional solvent molecules.

They involve host/guest stoichiometric ratios ranging from

1:3 (1a, 2b) via 1:4 (1b) and 1:5 (4a) to the unusually high

host:guest ratio of 1:6 in 2c, showing up to four additional

solvent molecule, respectively, for the stabilization of the

crystal packing. Hence, the ability for storage of high ratios

of solvent in the crystal structure of inclusion compounds in

some cases is a salient feature of the compound class. At

constant bulkiness of the terminal groups, this is likely to be

related to the length of the spacer element, but this is diﬃcult

to put in concrete terms. At any rate, a change in length

of the spacer element of the host obviously inﬂuences the

packing behavior as schematized in Figure 7. That is to say, the

crystal structures of 1a, 1b, and 4a are characterized by a

typical layer arrangement of host and guest molecules being

stacked in an alternating fashion. The host−guest stoichio-

metric ratios of 1:3, 1:4, and 1:5 of these structures,

respectively, indicate that diﬀerent patterns of noncovalent

bonding within the layers of guest molecules are present. The

donor−acceptor behavior of the included solvent in the crystal

structure of 2a leads to formation of discrete O−H···N bonded

host−guest aggregates; i.e., no layer formation is observed

in this structure. Here, the host molecules of adjacent com-

plexes interact via C−H···π bonding. Compared with 1b, the

elongation of the spacer element by an additional phenyl group

induces a channel-like cavity structure, in which the solvent

molecules are accommodated. Surprisingly, crystallization of 2

from THF leads to a 1:6 solvate 2c with the solvent molecules

incorporated in channels of the host lattice showing diﬀerent

dimensions and cross sections. Crystal formation of the diols

3 and 4 containing a diphenylethynyl and diethynylphenyl

unit as a spacer element, respectively, yields inclusion struc-

tures with a cisoid arrangement of the pentacyclic terminal

moieties, instead of transoid as for 1 and 2, giving the

molecules a bowl-like overall geometry. This is also a reason

to see that the combination of bulky terminal groups and a

narrow well-dimensioned spacer element enables interlocking

H

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 4. Packing diagrams of 2a (a) and 2b (b) including the speciﬁc hydrogen bond motif formed in the structure of 2b (indicated as shaded area).

Oxygens are displayed as dotted and nitrogen atoms as hatched circles. Nonrelevant hydrogen atoms have been omitted for the sake of clarity.

In panel a, the two disorder positions of the solvent molecule are indicated in bold and light style.

of the molecules to form a closed packing structure with the

solvent molecules either accommodated in closed lattice voids

(3a) or creating a layer structure (4a).

EXPERIMENTAL SECTION

■

General. Melting points are uncorrected. IR spectra were obtained

using a Nicolet 510A spectrometer. The Raman spectrum was per-

formed with a Bruker RFS 100/S spectrometer. H and ¹³C NMR

1

In summary, compared to the known solvent inclusion of

1-aryl substituted 2,3,4,5-tetraphenylcyclopentadien-1-ols being

simple monofunctional analogues,^18,19the present structurally

extended dumbbell-shaped host molecules 1−4 not only

give rise to a more diversiﬁed inclusion property but also to

unusually high stoichiometric ratios of the solvent included in

the majority of isolated crystals as a speciﬁc feature. This in

particular is likely to be beneﬁcial for future host design aiming

at the storage^7,30or the sensing^13,31of solvents by means of

crystalline materials.

spectra were recorded on a Bruker DPX 400 at 25 °C. Chemical shifts

are reported in ppm with TMS as an internal standard (δ = ppm).

Mass spectra were determined on Bruker ESQUIRE-LC 00084

(ESI) and MICROMASS ZABSPEC (FAB) instruments. The solvents

used were puriﬁed or dried according to common literature

procedures.³²

Starting Compounds. Tetracyclone,²¹4,4′-dibromotolane,^22,23

and 1,4-diethynylbenzene²⁵were prepared according to published pro-

cedures. 1,4-Dibromobenzene and 4,4′-dibromobiphenyl were purchased

from Aldrich.

I

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 5. Packing diagrams of 2c (a) and 3a (b). Layer and channel-type areas in the packing structure of 2c are marked by shading. Oxygen atoms

are displayed as dotted and sulfur atoms as cross-hatched circles. Dashed lines represent hydrogen bond interactions.

20

1

Synthesis of Host Compounds 1−4. General Procedure.

741, 700. H NMR (400 MHz, [D₆]DMSO) δ 6.10 (2H, s, OH),

Tetracyclone (5.76 g, 15 mmol) was added (at the beginning in

portions as a solid and after that as a solution in dry toluene) to a

stirred solution of the corresponding organyldilithium compound

(8.65 mmol), prepared from the respective aryl dibromide or

1,4-diethynylbenzene (8.65 mmol), at room temperature under

argon. Stirring of the mixture was continued until completion of the

reaction which is indicated by bleaching of the black-violet color of the

tetracyclone. The mixture was then quenched with water and acidiﬁed

(diluted hydrochloric acid). The organic layer was separated, ﬁltered,

and dried (Na₂SO₄). Evaporation of the solvent and extraction with

reﬂuxing toluene, in order to remove impurities, yielded the com-

pounds as powders. Details for the individual compounds are given

below.

6.82−7.13 (40H, m, phenyl-H), 7.39 (4H, s, phenylene-H). ¹³C NMR

(100.6 MHz, [D₆]DMSO) δ 89.4 (C−OH), 124.9−148.8 (CC, Ar).

MS (ESI) m/z Calcd for C₆₄H₄₆O₂: 847.1. Found: 847.2.

1,1′-(Biphenyl-4,4-diyl)bis(2,3,4,5-tetraphenylcyclopenta-

2,4-dien-1-ol) (2). Biphenyl-4,4′-diyldilithium (from 1,4-dibromobi-

phenyl and n-BuLi) was used to yield 6.56 g (82%) colorless powder.

Mp 278 °C (lit.²⁰278−280 °C). IR (KBr, cm⁻¹) 3545 (OH), 3079,

3059, 3028 (Ar−H), 1631, 1605, 1491 (CC, Ar), 1440, 1078

(C−O), 803, 746, 700. ¹H NMR (400 MHz, [D₆]DMSO) δ 5.84 (2H,

3

s, OH), 6.96−7.16 (40H, m, phenyl-H), 7.42 (4H, d, J_HH= 7.2 Hz,

phenylene-H), 7.62 (4H, d, J_HH= 7.2 Hz, phenylene-H). ¹³C NMR

3

(100.6 MHz, [D₆]DMSO) δ 88.4 (C−OH), 124.5−147.4 (CC, Ar).

MS (ESI) m/z Calcd for C₇₀H₅₀O₂: 923.2. Found: 923.3.

1,1′-(Ethynylene-di-4,1-phenylene)bis(2,3,4,5-tetraphenyl-

cyclopenta-2,4-dien-1-ol) (3). Ethynylene-di-4,1-phenylenedi-

lithium (from 4,4′-dibromotolane and n-BuLi) was used to yield

6.9 g (84%) colorless powder. Mp 290 °C. IR (KBr, cm⁻¹) 3534

(OH), 3084, 3059, 3022 (Ar−H), 1631, 1605, 1491 (CC, Ar),

1,1′-(1,4-Phenylene)bis(2,3,4,5-tetraphenylcyclopenta-2,4-

dien-1-ol) (1). 1,4-Phenylenedilithium (from 1,4-dibromobenzene

and n-BuLi) was used to yield 2.19 g (30%) colorless powder. Mp

290 °C (lit.²⁰290−291 °C). IR (KBr, cm⁻¹) 3550 (OH), 3079, 3053,

3028 (Ar−H), 1641, 1600, 1497 (CC, Ar), 1440, 1078 (C−O), 798,

J

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 6. (a) Illustration of the packing structure of 4a viewed along the crystallographic a-axis. Oxygen atoms are displayed as red, sulfur atoms as

orange circles. (b) Double strand-like supramolecular structure motif in 4a with coloring of the cyclic patterns of hydrogen bonding.

(c) Supramolecular interaction motif in the crystal structure of 4a.

Figure 7. Packing modes of the host molecules in the inclusion structures of 1a (a), 1b (b), 2a (c), 2b (d), 2c (e), 3a (f), and 4a (g). Guest

molecules are displayed as orange ellipses.

K

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

1440, 1078 (C−O), 803, 747, 705. Raman (neat powder, cm⁻¹) 2220

(6) Nassimbeni, L. R. In Encyclopedia of Supramolecular Chemistry;

Atwood, J. L., Steed, J. W., Eds.; CRC Press: Boca Raton, FL, 2004; pp

696−704.

(7) Nangia, A. In Nanoporous Materials; Lu, G. Q., Zhao, X. S., Eds.;

Series on Chemical Engineering; Imperial College Press: London,

2004; Vol. 4, pp 165−187.

(8) Comprehensive Supramolecular Chemistry; MacNicol, D. D.; Toda,

F.; Bishop, R., Eds.; Elsevier: Oxford, U. K., 1996; Vol. 6.

(9) Bishop, R. In Supramolecular Chemistry: From Molecules to

Nanomaterials; Gale, P. A., Steed, J. W., Eds.; Wiley: Chichester, U. K.,

2012; Vol. 6, pp 3033−3056.

(10) Weber, E. In Comprehensive Supramolecular Chemistry;

MacNicol, D. D., Toda, F., Bishop, R., Eds.; Elsevier: Oxford, U. K.,

1996; Vol. 6, pp 535−592.

(CC). ¹H NMR (400 MHz, [D₆]DMSO) δ 6.46 (2H, s, OH),

3

6.96−7.27 (40H, m, phenyl-H), 7.40 (4H, d, J_HH= 8.4 Hz,

3

phenylene-H), 7.54 (4H, d, J_HH= 8.4 Hz, phenylene-H). ¹³C NMR

(100.6 MHz, [D₆]DMSO) δ 89.3 (C−OH), 120.4 (C-CC), 125.4−

148.3 (CC, Ar). MS (ESI) m/z Calcd for C₇₂H₅₀O₂: 947.2. Found:

947.3.

1,1′-(1,4-Phenylene-diethynylene)bis(2,3,4,5-tetraphenylcy-

clopenta-2,4-dien-1-ol) (4). 1,4-Pheny-lene-diethynylenedilithium

(from 1,4-diethynylbenzene and n-BuLi) was used to yield 2.65 g

(34%) yellow powder. Mp 237 °C. IR (KBr, cm⁻¹) 3529 (OH), 3084,

3053, 3022 (Ar−H), 2221, 2195 (CC), 1631, 1610, 1496, 1488

(CC, Ar), 1445, 1072 (C−O), 804, 700. ¹H NMR (400 MHz,

[D₆]DMSO) δ 6.42 (2H, s, OH), 6.90−7.25 (40H, m, phenyl-H), 7.47

(4H, d, phenylene-H). ¹³C NMR (100.6 MHz, [D₆]DMSO) δ 81.1

(CC), 82.9 (CC), 92.4 (C−OH), 122.3 (C-CC), 125.3−143.9

(CC, Ar). MS (FAB) m/z Calcd for C₆₈H₄₆O₂: 895.1. Found: 895.

Preparation of Inclusion Compounds. Crystals of the inclusion

compounds 1a, 1b, 2a−2c, 3a, and 4a were obtained by slow

crystallization from solutions of the respective host compound in

the corresponding solvent or slow cooling the respective solutions

followed by slow evaporation of solutions if necessary.

X-ray Crystallography. The intensity data of the compounds

were collected on a Kappa APEX II diﬀractometer (Bruker AXS) with

MoK_αradiation (λ = 0.71073 Å). Reﬂections were corrected for

background, Lorentz and polarization eﬀects. Preliminary structure

models were derived by application of direct methods³³and were

reﬁned by full-matrix least-squares calculation based on F²for all

reﬂections.³³All hydrogen atoms were included in the models in

calculated positions and were reﬁned as constrained to bonding atoms.

The crystallographic data for the structures reported in this paper

have been deposited with the Cambridge Crystallographic Data Center

(CCDC) under http://ccdc.cam.ac.uk. Deposition numbers: CCDC

1452318 (1a), 1452317 (1b), 1452320 (2a), 1452319 (2b), 1452321

(2c), 1452322 (3a) and 1452323 (4a).

(11) Weber, E.; Czugler, M. In Molecular Inclusion and Molecular

Recognition − Clathrates II, Topics in Current Chemistry; Weber, E., Ed.;

Springer-Verlag: Berlin, 1988; Vol. 149, pp 45−135.

(12) Soldatov, D. V. J. Chem. Crystallogr. 2006, 36, 747−768.

(13) Katzsch, F.; Gruber, T.; Weber, E. Cryst. Growth Des. 2015, 15,

5047−5061.

(14) Weber, E. In Inclusion Compounds; Atwood, J. L., Davies, J. E.

D., MacNicol, D. D., Eds.; Oxford University Press: Oxford, U. K.,

1991; Vol. 4, pp 188−262.

(15) Batisai, E. F.; Nassimbeni, L. R.; Weber, E. CrystEngComm 2015,

17, 4205−4209.

(16) Weber, E.; Korkas, P. P.; Czugler, M.; Seichter, W. Supramol.

Chem. 2004, 16, 217−226.

(17) Muller, T.; Hulliger, J.; Seichter, W.; Weber, E.; Weber, T.;

̈

Wubbenhorst, M. Chem. - Eur. J. 2000, 6, 54−61.

̈

(18) Bourne, S. A.; Nassimbeni, L. R.; Niven, M. L.; Modro, A. M. J.

Inclusion Phenom. Mol. Recognit. Chem. 1992, 13, 301−310.

(19) Ruffani, A.; Seichter, W.; Weber, E. J. Inclusion Phenom. Mol.

Recognit. Chem. 2011, 70, 1−9.

(20) Broser, W.; Janzen, D.; Kurreck, H.; Braasch, D.; Oestreich, S.;

Plato, M. Tetrahedron 1976, 32, 1819−1827.

(21) Johnson, J. R.; Grummit, O. Org. Synth. 1955, Coll. Vol. III,

806−807.

ASSOCIATED CONTENT

* Supporting Information

The Supporting Information is available free of charge on the

ACS Publications website at DOI: 10.1021/acs.cgd.6b00383.

■

S

(22) Cadogan, J. I. G.; Inward, P. W. J. Chem. Soc. 1962, 0, 4170−

4178.

(23) Barber, H. J.; Slack, R. J. Chem. Soc. 1944, 612−615.

(24) Sonogashira, K. In Metal-Catalyzed Cross-Coupling Reactions;

Diederich, F., Stang, P. J., Eds.; Wiley-VCH: Weinheim, 1998.

(25) Rodriguez, J. G.; Martin-Villamil, R.; Cano, F. H.; Fonseca, I. J.

Chem. Soc., Perkin Trans. 1 1997, 709−714.

Complete atom numbering schemes and ring speciﬁca-

tions of the host molecules (PDF)

Accession Codes

(26) MacBride, J. A. H.; Wade, K. Synth. Commun. 1996, 26, 2309−

2316.

CCDC 1452317−1452323 contain the supplementary crystal-

lographic data for this paper. These data can be obtained free of

charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-

ing data_request@ccdc.cam.ac.uk, or by contacting The

Cambridge Crystallographic Data Centre, 12 Union Road,

Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

(27) Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond in

Chemistry and Structural Biology; IUCR Monographs on Crystallog-

raphy; Oxford University Press: New York, 1999; Vol. 9, pp 29−121.

(28) Nishio, M.; Umezawa, Y.; Honda, K.; Tsuboyama, S.; Suezawa,

H. CrystEngComm 2009, 11, 1757−1788.

(29) Bernstein, J.; Davis, R. E.; Shimoni, L.; Chang, N.-L. Angew.

Chem., Int. Ed. Engl. 1995, 34, 1555−1573.

AUTHOR INFORMATION

Corresponding Author

*E-mail: edwin.weber@chemie.tu-freiberg.de.

■

(30) Hertzsch, T.; Hulliger, J.; Weber, E.; Sozzani, P. In Encyclopedia

of Supramolecular Chemistry; Atwood, J. L., Steed, J. W., Eds.; CRC

Press: Boca Raton, FL, 2004; pp 996−1005.

(31) Eißmann, D.; Katzsch, F.; Weber, E. Tetrahedron 2015, 71,

7695−7705.

Notes

The authors declare no competing ﬁnancial interest.

(32) Leonard, J.; Lygo, B.; Procter, G. Praxis der Organischen Chemie;

VCH: Weinheim, 1994.

REFERENCES

■

(33) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr.

2008, 64, 112−122.

(1) Vittal, J., Zaworotko, M., Tiekink, E. R. T., Eds. Organic Crystal

Engineering; Wiley: New York, 2010.

(2) Desiraju, G. R. Angew. Chem., Int. Ed. 2007, 46, 8342−8356.

(3) Braga, D., Creponi, F., Eds. Making Crystals by Design: Methods,

Techniques and Applications; Wiley-VCH: Weinheim, Germany, 2007.

(4) Weber, E., Ed. Design of Organic Solids, Topics in Current

Chemistry; Springer-Verlag: Berlin, 1998; Vol. 198, pp 421−513.

(5) Herbstein, F. Crystalline Molecular Complexes and Compounds;

Oxford University Press: Oxford, 2005; Vol. 1, pp 421−513.

L

DOI: 10.1021/acs.cgd.6b00383

Cryst. Growth Des. XXXX, XXX, XXX−XXX

Article Doi

Crystal Inclusion Formation of a New Type of Dumbbell-Shaped Host Compound Featuring Two Bulky 2,3,4,5-Tetraphenylcyclopenta-2,4-dien-1-ol Terminal Groups Attached to a Linear Spacer Unit

DOI: 10.1021/acs.cgd.6b00383

Source and publish data:

Authors:

Article abstract of DOI:10.1021/acs.cgd.6b00383

Full text of DOI:10.1021/acs.cgd.6b00383

Products guided by the article

R&D Labs maybe for 40642-07-7

Relevant to this article

Hot Product