Self-assembly of semifluorinated dendrons attached to electron-donor groups mediates their π-stacking via a helical pyramidal column

DOI: 10.1002/chem.200501195

Self-Assembly of Semifluorinated Dendrons Attached to Electron-Donor

Groups Mediates Their p-Stacking via a Helical Pyramidal Column

Virgil Percec,*^[a]Martin Glodde,^[a]Mihai Peterca,^[c]Almut Rapp,^[b]Ingo Schnell,^[b]

Hans W. Spiess,^[b]Tushar K. Bera,^[a]Yoshiko Miura,^[a]

Venkatachalapathy S. K. Balagurusamy,^{[a, c]}Emad Aqad,^[a]and Paul A. Heiney^[c]

Abstract: Semifluorinated first-genera-

tion self-assembling dendrons attached

via a flexible spacer to electron-donor

molecules induce p-stacking of the

donors in the center of a supramolecu-

lar helical pyramidal column. These

helical pyramidal columns self-organize

in various columnar liquid crystal

phases that mediate self-processing of

large single crystal liquid crystal do-

mains of columns and self-repair their

intracolumnar structural defects. In ad-

dition, all supramolecular columns ex-

hibit a columnar phase at lower tem-

peratures that maintains the helical

pyramidal columnar supramolecular

structure and displays higher intraco-

lumnar order than that in the liquid

crystals phases. The results described

here demonstrate the universality of

this concept, the power of the fluorous

phase or the fluorophobic effect in self-

assembly and the unexpected generali-

ty of pyramidal liquid crystals.

Keywords: dendrimers · electron-

donor groups

self-assembly

· liquid crystals ·

Introduction

tained from discotic molecules alleviate some of the nega-

tive features of polymers and organic single crystals, the en-

gineering of their charge carrier properties requires the syn-

thesis of libraries of complex discotic molecules. Substantial

progress has been made on the design and synthesis of elec-

tron-donor discotic molecules,^[3]and the field has been re-

viewed.^[4]However, there are only limited examples of elec-

tron-acceptor discotic molecules.^[4c,f,5]Smectic LC phases

have been also shown to increase charge carrier mobility of

low molecular mass organic^[6]and macromolecular^[7]com-

pounds. The most recent advance in organic electronic ma-

terials was generated by combining the fields of supramolec-

ular chemistry, liquid crystals and molecular electronics to

generates the new area of supramolecular electronics.^[8]

Columnar LC phases of discotic molecules mediate the ar-

rangement of the aromatic part of the discs in a face-to-face

arrangement and thus provide the p–p stacking that is re-

sponsible for their increased charge carrier mobility. Howev-

er, columnar LC can also be self-organized from supramo-

lecular columns that are self-assembled from tapered rather

than from discotic molecules.^[9]The most notable examples

of tapered building blocks are low generation amphiphilic

dendrons that can be functionalized with a diversity of

groups at their apex.^[9]In a recent communication, we have

reported preliminary results on a novel strategy to mediate

the face-to-face arrangement of both electron-donor and

electron-acceptor organic molecules by their attachment to

Columnar liquid crystals (LC) have received interest as elec-

tronic materials after the discovery that hexagonal columnar

LCs obtained from discotic molecules exhibit charge carrier

mobilities between amorphous polymers and organic single

crystals.^[1]In addition to high charge carrier mobility, the

liquid crystalline state provides a mechanism to process

single crystal LC domains of electronic thin films that are

not accessible from organic single crystals. By contrast,

amorphous and semicrystalline electronically active macro-

molecules have good processability but display low charge

carrier mobility.^[2]Although hexagonal columnar LCs ob-

[a]Prof. V. Percec, Dr. M. Glodde, Dr. T. K. Bera, Dr. Y. Miura,

Dr. V. S. K. Balagurusamy, Dr. E. Aqad

Roy & Diana Vagelos Laboratories

Department of Chemistry, University of Pennsylvania

Philadelphia, PA 19104-6323 (USA)

Fax : (+1)215-573-7888

E-mail: percec@sas.upenn.edu

[b]Dr. A. Rapp, Dr. I. Schnell, Prof. H. W. Spiess

Max Planck Institute for Polymer Research

55021 Mainz (Germany)

[c]M. Peterca, Dr. V. S. K. Balagurusamy, Prof. P. A. Heiney

Department of Physics and Astronomy

University of Pennsylvania

Philadelphia, PA 19104-6396 (USA)

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Chem. Eur. J. 2006, 12, 6298 – 6314

FULL PAPER

the apex of a self-assembling semifluorinated first-genera-

tion dendron or minidendron.^[8b]Semifluorination mediates

the self-assembly of the first-generation dendrons via the

fluorophobic effect^[9b,10]and also protects the electronic active

core of the supramolecular column against moisture.^[8b,f,h]

Moreover, co-assembly of these functionalized dendrons be-

tween themselves and with complementary amorphous elec-

troactive polymers opens numerous strategies to program

various electronic functions of conventional organic and

macromolecular materials. This supramolecular electronic

system self-repairs its supramolecular structural defects and

is self-processable between various electrodes with a desir-

able arrangement of the supramolecular columns.

In this publication we discuss the scope and limitations of

this concept.^[8b]The effects of structural modifications of the

dendron, spacer and electroactive group from the apex of

the dendron on the self-assembly and self-organization pro-

cesses were examined and will be reported. We will show

that our strategy to supramolecular electronic materials

mediated by self-assembling dendrons is universal, simple

and compatible with a variety of electroactive groups. In ad-

dition, the supramolecular columnar structure of the liquid

crystal phase reported previously^[8b]is maintained with an

even higher degree of intracolumnar order in the lower tem-

perature columnar structure that is expected to display even

higher charge carrier mobilities than those reported pre-

viously.^[8b]The electroactive cores used in this study are well

known electroactive compounds. They include electron-

donors (D) with various shapes that display a wide range of

ionization potentials.

Results and Discussion

Synthesis: The structures of the dendrons containing elec-

tron-donating groups at their apex that will be discussed in

this paper are shown in Figure 1. The synthesis of

A

R

AHCTREUNG

taining an alkane or oligoethylene glycol spacer between the

acid and the electron-donor groups.

Scheme 1 outlines the synthesis of four new electron-

donor groups. 2-[2-(3,5-Dimethoxyphenyl)ethoxy]ethanol

(3) was synthesized by etherification of the commercially

available 3,5-dimethoxyphenol (1) with 2-(2-chloroethoxy)-

ethanol (2) in 57% yield. 3,5-(Dipyrrolidine-1-yl)phenol (4)

was prepared according to a literature procedure.^[11]Alkyla-

tion of 4 with 2-(2-chloroethoxy)ethanol (2) produced 2-{2-

[3,5-(dipyrrolidin-1-yl)phenyl]ethoxy}ethanol (5) in 25%

yield. The low yield obtained for 5 is due to the instability

of compound 4 under the alkylation conditions. Compounds

4 and 5 are sensitive to light and O₂and should be stored

under N₂in dark. The commercially available phenothiazine

(6) was sublimed and used immediately for the synthesis of

the electron-donating 2-(phenothiazine-10-yl-ethoxy)ethanol

(8). The latter was prepared in 53% yield according to a

modified literature procedure^[12]by the alkylation of pheno-

thiazine (6) with THP-protected 2-(2-chloroethoxy)ethanol

(7). In addition to the carbazole linked to diethylene glycol

spacer (2EO) reported previously,^[8b]the synthesis of a car-

Figure 1. Structures of self-assembling dendrons containing electron-donor groups and the results of the retrostructural analysis of their supramolecular

assemblies.

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www.chemeurj.org

6299

V. Percec et al.

bazole derivative attached to a

tetraethylene glycol spacer

(4EO) was also achieved. Thus,

the N-alkylation of the freshly

recrystallized carbazole (10)

with 2-{2-[2-(2-benzylethoxy)-

ethoxy]ethoxy}-p-toluene sulfo-

nate (9)^[13]was best performed

by using NaH in DMF at 508C.

Subsequent Pd/C catalyzed de-

benzylation afforded compound

11 in 24% yield.

The synthesis of the new den-

drons

(D1),

(D2),

(D3),

(D5)

ACHTREUNG

4EOCz (D10) was achieved in

moderate to high yield by N,N’-

dimethyldicyclohexylcarbodi-

imide (DCC)/4-dimethylamino-

pyridinium p-toluenesulfonate

(DPTS) mediated esterification

of the semifluorinated acid

12^[9b,10a]with the hydroxy-termi-

nated electron-donating com-

pounds 3, 5, 13, 8, and 11, re-

spectively (Scheme 2). The syn-

thesis of the semifluorinated

Scheme 2. Dendrimer precursors: i) DCC, DPTS, a,a,a-trifluorotoluene, 558C, 12 h.

the dendrons based on

A

acid

nated methylenic groups is shown in Scheme 3. The electro-

active dendrons based on (3,4,5)16F8G1-CO₂H (18) are ex-

A

(Scheme 2). The monohydration of 1,7-octadiene (14) under

hydroboration conditions produced oct-7-ene-1-ol (15) in

30% yield according to a modified literature procedure.^[14]

The Pd⁰-catalyzed addition of perfluorooctyliodide to 15

was performed similar to our previously reported proce-

dure.^[13]Reduction with LiAlH₄and subsequent bromination

of the corresponding alcohol produced compound 16 in

45% yield. Etherification of methyl gallate (17) with 16

(41% yield) followed by saponification produced the corre-

pected to provide higher intracolumnar order than those of

sponding acid (3,4,5)16F8G1-CO₂H (18) in 90% yield. The

N

esterification of carbazole derivative 2-[2-(carbazol-9-yl)-

ethoxy]ethanol (19)^[15]with the semifluorinated acid 18 pro-

duced dendron (3,4,5)16F8G1-2EOCz (D9) in 77% yield.

G

Thermal analysis by differential scanning calorimetry

(DSC): All dendrons were analyzed by a combination of dif-

ferential scanning calorimetry (DSC), thermal optical polar-

ized microscopy (TOMP) and X-ray diffraction (XRD) ex-

periments according to methods elaborated previously in

our laboratory.^[8b,h]The transition temperatures and the cor-

responding enthalpy changes (kcalmol^ꢀ1) were determined

by DSC with heating and cooling rates of 108Cmin^ꢀ1. The

assignment of various phases was done by a combination of

XRD and TOMP according to methods employed in our

laboratory.^[8b,16]Table 1 summarizes the transition tempera-

tures and the corresponding enthalpy changes for all self-as-

sembling dendrons. All dendrons self-assemble into supra-

Scheme 1. Synthesis of four new electron-donor groups: i) K₂CO₃, DMF,

708C, 12 h; ii) NaH, Bu₂O, 1108C; iii) HCl_aq, MeOH; iv) NaH, DMF,

508C, 3 h; v) H₂, Pd/C, EtOH/CH₂Cl₂, 258C, 24 h.

6300

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Chem. Eur. J. 2006, 12, 6298 – 6314

Semifluorinated Dendrons

FULL PAPER

EtNp affords only

a

monotropic phase. Similarly,

AHCTREUNG

shows columnar liquid crystalline phases in all DSC scans.

Modification of the core with rigid substituents also reduces

the LC temperature range. The dendron (3,4,5)12F8G1-

N

2EODMB containing two OCH₃groups attached to the aro-

matic core group is enantiotropic after the first heating scan,

but (3,4,5)12F8G1-2EODPB with two pyrrolidino groups re-

G

mains only monotropic. Structural modifications of the pe-

ripheral design of the semifluorinated dendron reduce the

temperature range of the LC phase but increase the melting

temperature. Thus, increasing the proportion of methylene

groups from (CH₂)₄-(CF₂)₈F to (CH₂)₈-(CF₂)₈F decreases the

temperature range of the LC phase, as seen by comparing

Scheme 3. Synthesis of 18 and D9: i) BH₃·THF, then NaOH, H₂O₂; ii) F-

A

U

AHCTREUNG

iv) HBr (48%), aliquate-336; v) K₂CO₃, DMF, 708C; vi) KOH, EtOH,

reflux then HCl_aq; vii) DCC, DPTS, a,a,a-trifluorotoluene, 558C, 12 h.

AHCTREUNG

108C). Nevertheless, as it will

be discussed later, the low tem-

Table 1. Thermal transitions and corresponding enthalpy changes of the lattices self-organized from supramo-

lecular columns containing electroactive dendrons.

perature

phase

of

AHCTREUNG

ꢀ1 [a]

Compound

(3,4,5)12F8G1-2EODMB

(3,4,5)12F8G1-2EODPB

(3,4,5)12F8G1-EtNp

(3,4,5)12F8G1-2EONp

(3,4,5)12F8G1-2EOPt

(3,4,5)12F8G1-BuPy

(3,4,5)12F8G1-2EOPy

(3,4,5)12F8G1-2EOCz

(3,4,5)16F8G1-2EOCz

(3,4,5)12F8G1-4EOCz

Thermal transitions [8C]and corresponding enthalpy changes [kcalmol

Heating 1st Cooling

]

ated from supramolecular col-

umns with high degree of intra-

columnar order that have the

potential to increase the charge

carrier mobility above the

range of values reported pre-

viously.^[8b]

io [b],[c]

io

r-c

G

F

77.9 (13.32) i^[d]

i 62 (0.31) F_r-c11 (3.21) F

r-c

io

19 (1.81) F 27 (0.81) F_r-c66 (0.48) i

r-c

io

^r-s

G

^[e]104 (14.21) i

i 50 (0.47) F_r-c11 (1.11) F

^r-s

io

^r-s

[f]

15 (1.11) F 49 (ꢀ10.22) F_h105 (4.33)

^r-s

io

^r-c

U

82 (10.03) i

i 49 (0.33) F_h19 (2.50) F

^r-s

io

^r-s

io

^r-s

27 (2.63) F 40 (ꢀ4.94) F 82 (9.68) i

^r-s

io

^r-c

E

48 (8.90) F_h75 (0.40) i

i 70 (ꢀ0.40) F_h16 (3.22) F

^r-c

io

24 (3.07) F_h74 (0.46) i

61 (8.21) F_h92.0 (0.37) i

25.4 (1.87)F^ð_h^ioÞ92 (0.37) i

^r-c

io

i 89 (0.39) F^ð_h^ioÞg16.0 (1.24) F

io

^r-s

E

Structural and retrostructural

analysis by X-ray diffraction:

Small-angle (Table 2) and wide-

angle X-ray diffraction (XRD)

(Table 3) studies on powder

and oriented fibers indicate

that most of these dendrons

form a 2D hexagonal columnar

LC phase (F_h) at high tempera-

ture. This is evidenced by three

sharp reflections with the indi-

ces (10), (11) and (20). The (10)

peak is very strong and the (11)

and (20) peaks are weak. The

diameters of the supramolecu-

lar columns range from 42.8 to

^r-s

io

^r-s

N

Fⁱ_h^o59 (8.20) F_h^io63 (ꢀ11.00) F_h83 (11.70) i

i 78 (0.51) F_h2 X^[g]

X 13 (1.30) F_h82 (0.67) i

io

^r-c

G

F

49 (11.01) F_h97 (0.53) i

ꢀ2 k 19 (2.30) F_h97 (0.59) i

i 92 (0.41) F_h7 F

^r-c

F

io

^r-c

R

Fⁱ_h^o39 (2.31) Fⁱ_h^o53 (9.62) F_h75 (1.01) i

i 71 (ꢀ0.81) F_h13 (4.91) k 6 X

X 13 k 21 (5.00) F_h75 (0.80) i

io

r-c

R

F

43 (4.42) F_h63 (0.33) i

44 (8.54) F_h63 (0.24) i

i 57 (0.32) F_h44 (8.62) F

i 76 (0.51) F_h13 (2.87) X

r-c

^r-c

io

F

E

X 21 (3.10) F_h81 (0.31) i

[a]Data from the first heating and cooling scans are on the first line and data from the second heating are on

the second line; [b] F_r-c, C2mm centered rectangular columnar lattice; [c]io: lattice with intracolumnar order;

[d]i isotropic; [e] F_r-s;p2mm simple rectangular columnar lattice; [f] F_h, p6mm columnar hexagonal lattice;

[g]X =unknown phase.

molecular columns that self-organize into various columnar

LCs. Hexagonal columnar p6mm (F_h) LC phases predomi-

nate. A centered rectangular columnar c2mm (F_r-c) LC

51.4 (Table 2). Many dendrons which form a 2D hexago-

nal columnar phase show an additional, closely related

phase at a lower temperature. This corresponds to a weak or

moderately strong endotherm in the DSC. In this phase,

peaks that were not observed in the 2D hexagonal columnar

phase appear. They are slightly broader indicating that there

is a fair amount of disorder in the supramolecular columns.

The retrostructural analysis of four supramolecular columns

by using methods elaborated previously in our laboratory^[9d]

phase was observed in the case of (3,4,5)12F8G1-2EODMB

A

and (3,4,5)12F8G1-2EODPB. In general, the replacement of

the flexible ether spacer by an aliphatic one decreases the

temperature range of the columnar LC phase and enhances

the tendency towards columnar phases with intracolumnar

order or even crystallization. For example, the diethylene

glycol spacer in

tropic LC phase, whereas the ethyl spacer

A

is summarized in Table 2. The number of dendrons forming

[9d,f,g]

A

a column stratum of 4.7

varied between 4.1 and 4.6.

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V. Percec et al.

Table 2. Structural and retrostructural analysis by XRD of supramolecular columns and their corresponding lattices generated from dendrons containing

donor groups.

[a]

Compound

Lattice

T

[8C]

d Spacings []

a or (a,b)

[]

1₂₀

[gcm^ꢀ3

]

m^[b]

io

^r-c

A

F

0

d₂₀(45.9) d₁₁(40.4) d₄₀(23.2) d₀₂(22.4) d₂₂(20.1)

92.7; 44.7^[c]

F_r-c

r-s

55

0

d₂₀(38.1) d₁₁(34.0) d₀₂(18.9) d₂₂(16.7)

d₁₀(40.3) d₁₁(32.1) d₀₂(28.9) d₂₀(20.2) d₂₂(16.2)

76.1; 37.7^[c]

39.8; 56.4^[d]

io

G

F

F_r-c

80

20

30

15

36

10

74

32

24

60

24

30

24

61

28

d₂₀(40.3) d₁₃(36.1) d₂₂(32.2) d₀₄(29.5) d₀₆(20.3) d₄₄(16.4)

d₁₀(40.3) d₀₁(33.7) d₁₁(25.7) d₀₂(16.5)

d₁₀(37.0) d₁₁(21.4) d₂₀(18.5)

d₁₁(43.7) d₂₀(39.0) d₃₁(28.9) d₄₀(19.4) d₁₃(16.4)

d₁₀(40.8) d₁₁(20.1) d₂₀(20.1)

d₁₀(38.9) d₀₁(32.6) d₂₀(18.9) d₂₁(17.0) d₁₂(15.0)

d₁₀(38.3) d₁₁(22.5) d₂₀(19.5)

d₁₀(39.8) d₁₁(22.8) d₂₀(19.8) d₂₁(15.0)

d₁₀(42.1) d₂₀(21.0)

d₁₀(39.0) d₁₁(22.3) d₂₀(19.2)

d₁₁(44.6) d₂₀(37.9) d₀₂(27.8) d₃₁(22.7) d₂₂(22.1) d₄₀(18.9) d₁₃(17.8)

d₁₀(42.5) d₁₁(24.2) d₂₀(20.9)

d₁₀(41.7) d₂₀(21.1)

d₁₀(39.0) d₁₁(22.4) d₂₀(19.5)

78.1; 121.0^[c]

40.6; 32.9^[d]

42.8^[e]

io

F

ACHTREUNG

^r-s

F_h

F

io

A

77.8; 51.4^[c]

46.8^[e]

^r-c

F_h

F

1.49

1.53

4.42

io

R

38.7; 32.8^[d]

44.6^[e]

r-s

F_h

Fⁱ_h^o

46.0^[e]

E

48.6^[e]

4.12

4.58

4.54

F_h

F

44.6^[e]

io

N

75.5; 55.07^[c]1.49

^r-c

F_h

48.6^[e]

N

Fⁱ_h^o

F_h

48.1^[e]

1.62

44.9^[e]

io

^r-c

R

F

d₁₁(48.3) d₂₀(44.0) d₀₂(28.9) d₃₁(26.3) d₂₂(24.1) d₄₀(22.0) d₁₃(18.7) d₄₂

(17.5)

d₁₀(44.6) d₁₁(25.8) d₂₀(22.3)

88.2; 57.7^[c]

F_h

55

56

51.4^[e]

49.9^[e]

A

d₁₀(43.3) d₂₀(21.6)

pﬃﬃﬃ

[a] 1₂₀=experimental density at 208C. [b]Number of monodendrons per 4.7 column stratum m=( 3N_AD²t₁)/2M(Avogadroꢁs number N_A=6.0220455

10²³mol^ꢀ1, the average height of the column stratum t=4.7 , and M=molecular weight of monodendron. [c] c2mm=centered rectangular (F_r-c) lattice

parameters a and b; a=hd, b=kd; (h0) and (k0) from diffractions. [d] p2mm=simple rectangular columnar (F_r-s) lattice parameters a and b; a=hd, b=

kd; (h0) and (k0) from diffractions. [e] p6mm=hexagonal columnar (F_h) lattice parameter; a=2hd₁₀₀

pﬃﬃﬃ

3; hd₁₀₀i = d₁₀₀

pﬃﬃﬃ

3d₁₁₀

pﬃﬃﬃ pﬃﬃﬃ

4d₂₀₀+ 7d₂₁₀)/4.

i

+

dendrons in these pyramidal su-

pramolecular dendrimers varies

between 42 and 228 (Table 3,

Figure 2). Their short range hel-

ical pitch (s₂in Figure 2) is be-

tween 5.0 and 5.5 (Table 3).

In agreement with NMR results

to be discussed later, this heli-

cal pyramidal arrangement of

the dendrons mediates the face-

to-face arrangement of the elec-

tron-donor groups at a distance

that varies between 3.9 and

Table 3. Structural and retrostructural analysis by wide angle XRD of aligned fibers.

Compound

Phase

T

[8C]

Tilt angle

[8]

Short-range helical pitch p

[]^[a]

p-Stack distance

[]^[b]

A

F_h

50

40ꢁ10

5.3

4.1

A

32

81

48

65

25

40

20ꢁ23

42ꢁ10

–

50ꢁ10

60ꢁ8

33ꢁ22

–

3.9

4.0

3.9

4.2

F_h

5.3

5.5

4.9

5.3

(3,4,5)12F8G1-2EOPy F_h

A

io

A

F

^r-c

A

[a]Determined from s₂in Figure 2. [b]Determined from s₁in Figure 2.

This noninteger number is expected to induce a helical con-

formation of the dendrons in the supramolecular column.^[8b]

Oriented fibers of these dendrons were studied by small-

and wide-angle XRD.^[8b]Fibers were extruded from a mini

extruder in the LC phase, cooled to room temperature, and

then kept in a temperature-controlled oven for recording

the XRD patterns at different temperatures. Figure 1 sum-

marizes the analysis of the donor group-containing den-

drons. In the well-oriented fibers, sharp reflections with the

large maximum in intensity near the equator (perpendicular

to the extrusion direction) were observed in the small-angle

region in the LC phase. The wide-angle XRD results ob-

tained on oriented fibers are summarized in Table 3. All su-

pramolecular columns consist of pine-tree like or pyramidal

helical arrangement of dendrimers.^[8b]The tilt angle of the

4.2 (Table 3). The distance from the s₂feature in XRD to

the equatorial axis (Figure 2 g,h,i) gives the pitch value (p)

while the distance from s₂to the meridional axis gives the

radius of rotation of the part of the structure that generates

the helical feature. Pitch values larger than 5 (Table 3)

would be expected to show more than one helical feature.

The current data exhibits a single order of diffraction s₂and

therefore, is in agreement with the proposed assignment.

The distance between the electron-donor groups determines

the charge carrier mobility in the core of the supramolecular

columns. These XRD experiments provide only a limited

amount of structural information at the molecular level in

the supramolecular structure. Therefore, the XRD analysis

was complemented by NMR studies carried out in solid

state and in solution.

6302

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Chem. Eur. J. 2006, 12, 6298 – 6314

Semifluorinated Dendrons

FULL PAPER

ing of the donor groups is ob-

served (see the s₁feature indi-

cated in Figure 2g, h and j).

However, intracolumnar order

io

is much higher in the

column of the

2EOCz than the F_hcolumn of

(3,4,5)12F8G1-2EOCz. Fig-

F

^r-c

A

AHCTREUNG

ure 2j shows that both s₁and s₂

features are sharper for the

(3,4,5)16F8G1-2EOCz than the

A

or

A

The

order along the column increas-

es from approximately four

layers, for the

2EOPt or

2EOCz, to more than 24 layers

for (3,4,5)16F8G1-2EOCz; the

ACHTREUNG

AHCTREUNG

order correlation values were

calculated from the full width

half maximum of the s₂feature

for the three systems presented

in Figure 2j. All low tempera-

ture phases from Table 1 main-

tain the intracolumnar order of

their higher temperature liquid

crystal phase either in a 2D lat-

tice with intracolumnar order

as in the example discussed

here or in 3D lattice with intra-

columnar order. Therefore, it is

expected that even higher

charge carrier mobility than the

one reported before^[8b]must be

observed for these phases.

Figure 2. Supramolecular columns self-assembled from

G

N

top-view of one column stratum from

column from (3,4,5)12F8G1-2EOPt; c) top-view of the column from

column stratum of the column from (3,4,5)16F8G1-2EOCz; e) side-view of the cross-section of the column

with intracolumnar order from (3,4,5)16F8G1-2EOCz; f) details of the (3,4,5)12F8G1-2EOPt (left) and

(3,4,5)16F8G1-2EOCz (right) core-core stacking in the column without (left) and with (right) intracolumnar

order; g), h) and i) XRD of the aligned samples of (3,4,5)12F8G1-2EOPt, (3,4,5)16F8G1-2EOCz and

(3,4,5)12F8G1-2EOCz; j) stack XRD plot along the meridional region for the (3,4,5)12F8G1-2EOPt,

(3,4,5)16F8G1-2EOCz and (3,4,5)12F8G1-2EOCz indicating the position of s₁and s₂features; k) and l) sche-

ACHTREUNG

G

ACHTREUNG

Structural analysis by magic

angle spinning NMR spectro-

scopy: In order to obtain a

better understanding of the

structure and packing effects,

AHCTREUNG

U

ACHTREUNG

N

ACHTREUNG

A

ACHTREUNG

C

ACHTREUNG

four dendrons

2EOPy, (3,4,5)12F8G1-2EONp,

(3,4,5)12F8G1-BuPy and

(3,4,5)12F8G1-EtNp, were stud-

ied by magic angle spinning

(3,4,5)12F8G1-

matic of the hexagonal columnar and centered rectangular columnar phases; only the core region is shown.

tilt-dendron tilt, (hk0) reflections of the hexagonal or rectangular columnar phases, s₁core–core stacking in

agreement with NMR data s₂-dendron helical feature.

AHCTREUNG

Molecular models of the supramolecular pyramidal columns

in the LC and higher order phases: Molecular models of the

supramolecular helical pyramidal columns were developed

based on the XRD results for the F_hphase of

(MAS) NMR spectroscopy and compared with their non-

dendritic precursors 4-pyren-1-yl-butan-1-ol (PyBuEtOH)

and 2-naphthalen-1-yl-ethanol (NpEtOH). Figure 3 shows

the proton spectra of these compounds in their solid glassy

state, LC phase, in isotropic melt and in CDCl₃solution.

The resolution of the spectra increases with temperature

from the solid state via the columnar LC phase to the melt.

This can be explained by an increase in the mobility of the

molecules with temperature, leading to a decrease in the ef-

fective dipolar couplings (due to motional averaging) and

A

io

dered intracolumnar phase F of

io

^r-c

order in the F_hand F phase is shown in Figure 2b and e.

In Figure 2f the left column belongs to the F_hand the right

io

^r-c

column to the F phase. In both cases, the 3.9 p–p stack-

Chem. Eur. J. 2006, 12, 6298 – 6314

ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

6303

V. Percec et al.

By comparison of the solu-

tion spectra to the bulk spectra

(solid, LC and melt), it be-

comes apparent that there are

p-shifts present to lower fre-

quencies for all resonances (ar-

omatic, OCH₂and alkyl) in all

six molecules, as indicated by

the white arrows in Figure 3.

Generally, similar p-shifts mean

similar p-electron densities sur-

rounding the respective proton

in a molecular assembly, point-

ing at a similar packing of the

molecules. Comparing the p-

shifts of the aromatic, OCH₂

and alkyl groups in each mole-

cule for the melt, the LC (F_h)

and the intracolumnar ordered

solid phase, two important

points are to be noted: i) for

A

and

AHCTREUNG

shifts observed for the aromatic

and the OCH₂R protons in-

crease when going from the in-

tracolumnar ordered solid to

the LC phase, but remain simi-

lar for the transition to the

melt. Therefore, the p-electron

density of the LC phase and the

melt must be comparable, sug-

gesting a similar arrangement

of the molecules in both phases.

Hence, the columnar structure

of the liquid crystalline phase is

expected to persist in the melt.

The difference in p-shifts ob-

served for the solid and the LC

phase can be explained in terms

Figure 3. ¹H One-pulse spectra of molecules

(3,4,5)12F8G1-BuPy (c), (3,4,5)12F8G1-EtNp (d), PyBuOH (e) and NpEtOH (f) in the intracolumnar ordered

solid (glassy) state, the hexagonal columnar LC phase and the melt recorded at 30 kHz MAS. The solution

spectra were measured in CDCl₃. The white arrows indicate the p-shifts present in the solid-state, the liquid

crystalline phase and the melt. The star (*) refers to residual CHCl₃signal.

A

G

A

ACHTREUNG

hence causing less broadening of the resonance lines. Com-

paring the spectra in the LC phase, much narrower peaks

of a slightly different packing of the molecules in the

column. In the intracolumnar ordered solid phase, the as-

sembly might be more kinetically controlled, while in the

LC phase the thermodynamically preferred arrangement is

are observed for

N

G

2EONp than for

ACHTREUNG

width shows that the longer and more flexible ethyleneoxy

spacer allows a greater mobility of the molecules in the LC

phase as discussed in detail below. Since the LC phase of

achieved. ii) For

A

G

EtNp the observed p-shifts are comparable for all phases.

Therefore, the p-electron density and, thus, also the molecu-

lar assembly in the column are similar in all phases. For a

quantitative investigation of the p-shifts, it is necessary to

compare the chemical shift of the individual CH_ngroups ob-

served in solution with the corresponding chemical shift in

the bulk. Therefore, assignment of the different peaks was

carried out by 2D Double Quantum (DQ) spectra in addi-

tion to the relative intensities of the peaks. Table 4 summa-

rizes the chemical shift values of the different CH_ngroups

and the resultant p-shifts for all six molecules.

A

sample, is rather unstable, it could not be detected by NMR.

Figure 3d shows similar proton spectra at 10 and 608C upon

heating the sample. Thus, the intracolumnar ordered solid

or glassy state of

ACHTREUNG

peratures as compared to

AHCTREUNG

a columnar LC phase at 608C and hence a significantly nar-

rower linewidth. Table 4 summarizes the chemical shift

values of the different CH_ngroups and the resultant p-shifts

for all six molecules.

6304

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Chem. Eur. J. 2006, 12, 6298 – 6314

Semifluorinated Dendrons

FULL PAPER

Table 4. ¹H NMR Chemical Shifts Observed for the Different CH and CH₂Groups of

(3,4,5)12F8G1-2EOPy,

A

the melt in the spectrum in Fig-

ure 3a could be assigned, and

the result agrees well with the

relative intensities of the

proton peaks. The peaks of the

A

G

A

Solution d(¹H) Melt d(¹H)

[ppm] [ppm]

p shift Dd

[ppm]

Solution d(¹H) Melt d(¹H)

p shift Dd

[ppm]

A

G

other

three

molecules

pyrene/

napthalene

arom CH (den- 7.2

dron)

7.8–8.2

6.9–7.4

~0.9

7.2–7.8

7.1

6.8–7.5

~0.4

A

6.4

0.8

6.7

0.4

AHCTREUNG

OCH₂R

OCH₂CH₂

(spacer)

3.9

4.2

2.9

3.6

1.0

0.6

3.9

4.2

3.1

3.9

0.8

0.3

butan-1-ol (PyBuOH) and 2-

naphthalen-1-yl-ethanol

OCH₂CH₂

(spacer)

OCH₂CH₂

(spacer)

4.2

3.7

3.0

3.4

0.5

4.1

3.8

3.3

3.5

0.3

3.6

0.6

3.5

0.2

(NpEtOH) the assignment is

obvious. The proton chemical

shifts in solution and in the

melt are summarized in Table 4.

Looking at the p-shifts ob-

served for the polycyclic aro-

matic protons (pyrene and

naphthalene) listed in Table 4,

Py-/Np-CH₂

4.2

0.8

3.9

0.4

N

ACHTREUNG

pyrene/

napthalene

arom CH (den- 7.2

dron)

OCH₂R

7.7–8.2

6.9–7.4

~0.8

0.6

7.2–8.1

7.0

6.6–7.5

~0.6

0.5

6.6

6.5

3.9

4.3

3.3

3.0, 3.2^[a]

3.8

2.5

0.9, 0.7^[a]

0.6

0.8

3.8

4.5

3.4

3.1, 3.3^[a]

4.0

2.8

0.7, 0.5^[a]

0.5

0.6

CH₂(spacer)

Py/Np-CH₂

the

shifts

observed

for

PyBuOH

6.3–6.8

NpEtOH

6.2–7.0

A

and

pyrene/

7.8–8.3

1.5

7.2–8.0

3.5

1.0

(3,4,5)12F8G1-BuPy (Dd=0.9

and 0.8 ppm, respectively) are

more pronounced than for

naphthalene

CH₂(“spacer”)

3.5

1.8

2.1

0.5

1.4

1.3

2.5

A

and

[a]The first and second value correspond to the 3,5 and 4-substituted OCH ₂R groups on the aromatic ring, re-

spectively.

(3,4,5)12F8G1-EtNp (Dd=0.4

and

0.6 ppm,

respectively;

Table 4). These p-shifts must be

The two-dimensional DQ spectra in Figure 4 facilitate the

assignment of the different resonances, because they provide

an effect of the stacking of the pyrene and naphthalene

rings. Therefore, it is not surprising that the pyrene rings,

being a larger polycyclic aromatic unit, induce stronger p-

shifts than the naphthalene rings. This is also in good agree-

ment with the X-ray diffraction data, since it shows a slight-

1

information about through-space H–¹H proximities. If two

protons are in close proximity in the material, they will

share the same double-quantum frequency, which is the sum

of the single quantum frequencies of the two nuclei in-

volved. Therefore, different proton sites that are in close

proximity appear as so-called cross peaks in a DQ spectrum.

ly smaller p–p-stacking distance for

A

than for (3,4,5)12F8G1-2EONp (Table 3). For the aromatic

AHCTREUNG

protons of the dendron, p-shifts similar to those of the poly-

Looking at the spectrum of

A

cyclic aromatic protons are observed. Again, they are larger

parent that the diagonal and cross-peaks between d 6.9 and

7.4 ppm must arise from the pyrene core of the molecule

(marked purple in the spectrum), while the resonance at

6.4 ppm belongs to the two aromatic protons of the den-

dron. As expected, the latter shows a cross-peak to the adja-

cent OCH₂R groups (2.9 ppm) of the alkyl chains (depicted

in dark green) and, in addition, also a weak cross-peak to

other groups of the alkyl chains (depicted in light green).

The cross-peaks marked in blue at 3.7–3.6 and 3.0 ppm cor-

respond to the resonances of the neighboring groups in the

spacer. The orange region in the DQ spectrum (Figure 4) in-

dicates cross-peaks between the OCH₂R and the other CH₂

groups of the alkyl chains. Finally, there is a weak cross-

peak observed between the resonances at d 8.4 and 3.4 ppm

(marked pink). Hence, d 3.4 ppm must be the chemical shift

belonging to the pyrene-CH₂protons, since it is the only

one expected to show a proximity to protons of the pyrene

ring. Thus, all the resonances observed for the LC phase and

for

0.8 and 0.6 ppm, respectively) than for

2EONp and (3,4,5)12F8G1-EtNp (Dd = 0.4 and 0.5 ppm,

A

ACHTREUNG

AHCTREUNG

respectively). Without taking the possibility of backfolding

into account, the p-shifts observed for the aromatic protons

of the dendron can only be induced by the aromatic rings of

neighboring dendrons. A shift of 0.8–0.4 ppm to lower fre-

quencies can be induced by a single aromatic ring located

above or below the respective proton, at a distance of 3.5–

4.5 .^[17]This suggests a helical arrangement that supports

the XRD results. In this assembly one aromatic proton of

the dendron is located underneath the aromatic ring of the

adjacent dendron at an average distance of approximately

3.5–4.5 (depending on the molecule). The other aromatic

proton lies above the aromatic ring of the neighboring den-

dron on the other side, also at an average distance of ap-

proximately 3.5–4.5 .

Chem. Eur. J. 2006, 12, 6298 – 6314

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6305

V. Percec et al.

cyclic aromatic core. Neverthe-

less, the p-shifts observed for

the spacer groups are on aver-

age weaker. Therefore, the

spacer unit must be spatially

separated to

a large extent

from the polycyclic aromatic

core and the dendritic unit,

which is discussed in more

detail below.

With respect to the OCH₂R

groups another interesting fea-

ture should be mentioned. The

spectra of

A

and (3,4,5)12F8G1-EtNp show

AHCTREUNG

two different resonances for the

OCH₂R groups in the melt and

LC

phase,

while

for

A

and

(3,4,5)12F8G1-2EONp only one

resonance is observed. These

two resonances can be attribut-

ed to different p-shifts experi-

enced by the OCH₂R groups in

3,5- and 4-position on the den-

dritic aromatic ring that depend

on the spacer unit. Short and

rigid spacer units, as in

A

and

AHCTREUNG

arrangement of the dendrons in

the column where the 3,5- and

4-OCH₂R protons experience

different p-shifts from neigh-

Figure 4. Two-dimensional double-quantum (DQ) spectra of

A

G

A

ACHTREUNG

its LC phase is not stable. The spectra were recorded at 60–808C, at 30 kHz MAS with an excitation time of boring aromatic rings, while

four rotor periods (t_exc=4t_R) for (3,4,5)12F8G1-EOPy and (3,4,5)12F8G1-2EONp and two rotor periods

(t_exc=2t_R) for (3,4,5)12F8G1-BuPy and (3,4,5)12F8G1-EtNp.

A

ACHTREUNG

longer and more flexible

A

ACHTREUNG

spacers, as in

ACHTREUNG

2EOPy and

ACHTREUNG

2EONp, give rise to an arrange-

ment of the dendritic groups where all OCH₂R groups expe-

rience the same p-shifts.

The resonances between d 2.8 and 4.5 ppm in Figure 4

correspond to the OCH₂R and the spacer protons. Again,

larger p-shifts are observed for the two molecules with a

pyrene core than for the molecules with a naphthalene core.

Comparing the different resonances listed in Table 4, it is

apparent that the OCH₂R protons of the alkyl chains experi-

ence stronger p-shifts than the spacer protons. Out of the

protons of the spacer, the group next to the pyrene or naph-

thalene ring (Py-/Np-CH₂in Table 4) experiences the most

pronounced p-shifts. This is not surprising, because the

pyrene and naphthalene rings are displaced with respect to

each other in the column, so that the Py/Np-CH₂groups are

influenced by the shielding effects of the pyrene/naphtha-

lene rings above and below. From a sterical point of view

and neglecting backfolding effects, the OCH₂R groups can

only experience ring-current effects from dendritic aromatic

rings of neighboring molecules, while the groups of the

spacer can also be influenced by the p-electrons of the poly-

Larger p-shifts are also observed for PyBuOH (Dd=

1.5 ppm) as suppose to NpEtOH (Dd=1.0 ppm) listed in

Table 4. When comparing PyBuOH and NpEtOH with the

respective dendritic molecules, however, significantly larger

p-shifts are observed for those precursors. This can be ex-

plained in terms of a higher p-electron density that arises

from a different not columnar packing of the molecules.

Therefore, this demonstrates that the columnar structure is

induced primarily by the dendrons and not by the polycyclic

aromatic rings.

Separation of aromatic and aliphatic region: A helical-type

arrangement of the molecules suggests a separation of the

polycyclic aromatic core from the dendritic groups. This ar-

rangement is supported by the relatively weak p-shifts ob-

served for the spacer protons mentioned above. For

6306

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Chem. Eur. J. 2006, 12, 6298 – 6314

Semifluorinated Dendrons

FULL PAPER

A

G

the typical distance between two neighboring protons on an

aromatic ring is 2.74 .^[20]Thus, an immobile C–H segment

is characterized by a dipole–dipole coupling of D_C–H/2p =

21.0 kHz and an immobile aromatic ring by a ¹H dipole–

dipole coupling of D_H–H/2p = 8.0 kHz. These couplings are

reduced when molecular motions occur on timescales below

10^ꢀ6s.^[17,21]By relating the measured (reduced) dipole–

dipole coupling to the immobile case, a dynamic order pa-

rameter S can be determined for individual segments, where

S=1 represents a perfectly immobile segment and S=0 iso-

tropic motion.

ACHTREUNG

Figure 4d two different cross-peaks can be distinguished be-

tween aromatic and aliphatic protons. The cross-peak de-

picted in light green can be explained by a spatial proximity

of the aromatic protons of the dendron and the alkyl chain,

analogous to

U

2EONp. The cross-peak marked light blue, however, indi-

cates a proximity between the naphthalene protons and the

alkyl chain. Such proximity could arise from a backfolding

1

Starting with H,¹H DQ-spinning sideband patterns in the

intracolumnar ordered solid phase (Figure 5), similar pat-

terns are observed for the pyrene or naphthalene protons of

the four molecules. A coupling of D_H–H/2p = 8.0 kHz is ex-

tracted which corresponds to the full dipole–dipole coupling

expected for two neighboring protons (r_H–H= 2.47 ). This

yields an order parameter of S_hom=1.0. On the NMR time

scale the pyrene or naphthalene rings are therefore perfectly

immobile in their stack. The fitted sideband patterns are ob-

tained from numerical four-spin calculations using the Simp-

son program.^[22]To determine the dipole–dipole coupling of

two adjacent protons (2) and (3) in a pyrene or naphthalene

ring (marked by the large grey arrow in the inset of

Figure 5), the couplings to the neighboring protons on either

side (1) and (4) also were taken into account. Thus, a four-

spin system with dipole–dipole couplings of D_H–H/2p =

8.0 kHz for neighboring protons (H(1)–H(2), H(2)–H(3)

and H(3)–H(4)), D_H–H/2p = 1.3 kHz for every next neigh-

bor (H(1)–H(3) and H(2)–H(4)) and D_H–H/2p=0.4 kHz for

H(1)–H(4) is calculated for an excitation time of four rotor

periods, t_exc= 4t_Ryielding the sideband patterns depicted

in grey in Figure 5. These are in very good agreement to the

experimental patterns.

of some molecules. In the case of (3,4,5)12F8G1-BuPy (Fig-

G

ure 4c) only one cross-peak is observed between the aromat-

ic and the alkyl protons. This could either arise from a prox-

imity of the dendritic aromatic protons and the alkyl chains

(light green) or the pyrene protons and the alkyl chains

(light blue) or a superposition of both. The corresponding

cross-peaks on the alkyl side of the 2D DQ spectrum are

missing. This is a phenomenon often observed in the tail

region of strong aliphatic peaks. It can be attributed to spec-

tral distortions due to a mobility of the alkyl chains on the

NMR time-scale.^[18,19]Again, this indicates the possibility of

a backfolding of some molecules in the column. The proper-

ties of the columnar assembly, however, do not seem to be

influenced very significantly by such a backfolding of mole-

cules. Also, the backfolding of

A

ACHTREUNG

shifts observed for the aromatic protons of the dendron and

the OCH₂R groups (Table 4). If it did, the proximity to the

polycyclic aromatic core would cause larger p-shifts than in

A

N

A

U

Knowing that the polycyclic aromatic rings are immobile

in the intracolumnar ordered solid phase, a heteronuclear

dipole–dipole coupling of D_C–H/2p=21.0 kHz is expected for

the pyrene and naphthalene CH groups. Indeed, couplings

there are indications of a backfolding of molecules in the

column. However, backfolding is not observed for

A

N

of D_C–H/2p

=

(20.5ꢁ0.5)ꢀ(21.4ꢁ0.5) kHz are extracted

A

N

from REPT-HDOR spinning sideband patterns (not shown),

corresponding to order parameters of S_het=0.98–1.02.

For the aromatic CH group of the dendron, heteronuclear

dipole–dipole couplings of D_C–H/2p=19.0–21.0 kHz are de-

a much better spatial separation of the dendritic and polycy-

clic aromatic moieties of the molecules and prevents back-

folding phenomena much more efficiently.

termined

for

molecules

A

Investigation of molecular dynamics: We also investi-

A

ACHTREUNG

gated the molecular dynamics of the four dendritic mole-

shown in Figure 6. These couplings correspond to order pa-

rameters of S_het=0.90–1.0. Quite clearly, not only the poly-

cyclic aromatic rings, but also the dendritic units must be

rather immobile in the solid phase.

cules

N

G

U

ACHTREUNG

clear (¹H,¹H) and heteronuclear (¹H,¹³C) MAS NMR spin-

ning sideband patterns. These sideband patterns are a sensi-

tive measure for individual homonuclear and heteronuclear

dipole–dipole couplings (D_H–Hand D_C–H), which are subject

to motional averaging effects. The measured dipole–dipole

couplings are compared to coupling values of immobile seg-

ments such as CH, CH₂, CH₃or a phenyl ring, which are cal-

Turning to the LC phase, only homonuclear but no heter-

onuclear spinning sideband patterns could be recorded due

to the poor ¹³C signal intensity. From the DQ spinning side-

band patterns in Figure 7, recorded at ~608C, it can be seen,

that the pyrene and naphthalene rings are not immobile any

more in the stack. For

(3,4,5)12F8G1-BuPy a residual ¹H

A

culated from known distances between the nuclei. The typi-

dipole–dipole coupling of D_H–H/2p = 5.1 kHz is extracted.

This corresponds to a dynamic order parameter of S_hom

1

cal H ¹³C bond length of CH_ngroups is r_C–H=1.13 , while

ꢀ

Chem. Eur. J. 2006, 12, 6298 – 6314

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www.chemeurj.org

6307

V. Percec et al.

is a small angle motion of ap-

proximately ꢁ208.^[23]Figure 7

demonstrates clearly that the

aromatic

cores

of

A

and

AHCTREUNG

be attributed to the different

spacer. The residual ¹H,¹H

dipole–dipole coupling extract-

ed from the sidebands of

A

and

(3,4,5)12G1-2EONp is D_H–H/2p

<

0.6 kHz and results in an

order parameter of S_hom< 0.08.

Recalling the spectra in

Figure 3 the higher mobility of

Figure 5. ¹H,¹H DQ spinning sideband patterns of the polycyclic aromatic core (pyrene/naphthalene) of

(3,4,5)12F8G1-2EOPy, (3,4,5)12F8G1-2EONp, (3,4,5)12F8G1-BuPy and (3,4,5)12G1-EtNp in the intracolum-

molecules

ACHTREUNG

G

ACHTREUNG

2EOPy

and

ACHTREUNG

nar ordered solid phase at 108C, recorded under MAS at 30 kHz and an excitation time of four rotor periods

(t_exc=4t_R). The black and grey lines represent experimental and calculated data, respectively. The insert de-

2EONp in the LC phase, as

compared to (3,4,5)12F8G1-

1

AHCTREUNG

picts schematically the dipole–dipole couplings between four H spins in a pyrene or naphthalene ring.

BuPy, is already apparent from

the much narrower lines. Such a

large mobility of the pyrene

and naphthalene rings cannot

be explained by an axial rota-

tion or some other in-plane

motion, but must rather be due

to a fairly large out of plane

motion of the rings. Since the

LC phase is hexagonal colum-

nar, this motion must occur

within the stack, without de-

stroying the columnar arrange-

ment. Thus, the stability of the

columns must be attributed to

the dendritic units, while the p-

interactions between pyrene

and naphthalene molecules in

the center of the column only

Figure 6. ¹H,¹³C REPT-HDOR spinning sideband patterns of the aromatic CH groups of

2EONp, (3,4,5)12F8G1-BuPy and (3,4,5)12G1-EtNp in the intracolumnar ordered solid phase at 108C, record-

ed under MAS at 30 kHz and a recoupling time of two rotor periods (t_rcpl=2t_R) for (3,4,5)12F8G1-2EONp

and (3,4,5)12F8G1-BuPy and t_rcpl=3t_Rfor (3,4,5)12G1-EtNp. The black and grey lines represent experimental

and calculated data, respectively. The coupling vector is indicated in the insert.

(3,4,5)12F8G1-

play a minor role. In this way, a

rather large out of plane

motion of the pyrene and naph-

thalene rings can be explained,

U

ACHTREUNG

AHCTREUNG

H

ACHTREUNG

which does not affect the over-

all columnar structure because

ꢂ0.65, showing that the pyrene rings of

A

it is determined by the dendritic units. Such a defined pack-

ing of the dendritic units in the column certainly restricts

the motions possible for the polycyclic aromatic rings in the

core of the column, where a shorter and more rigid spacer

BuPy display some mobility in the p-stack. A fast axial rota-

tion of the molecules in the stack can be excluded, because

it would yield an order parameter of S_hom=0.5, as discussed

in reference [3b]. Moreover, the dendritic moieties of the

molecules are expected to stabilize the columnar packing

significantly, which makes a rotation around the axis of the

column highly unlikely anyway. Thus, the most probable

motion of the polycyclic aromatic rings in the central stacks

as in

pyrene and naphthalene rings to a larger extent than a

longer more flexible spacer as in (3,4,5)12F8G1-2EOPy and

(3,4,5)12G1-2EONp. In this way, the different type of

spacers can account for the significantly different dynamical

A

AHCTREUNG

6308

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ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2006, 12, 6298 – 6314

Semifluorinated Dendrons

FULL PAPER

ize in the hexagonal columnar

lattice containing a mixture of

backfolded and correctly ar-

ranged stacks of aromatic

donors. The backfolded donors

are visualized by NMR while

the correctly folded units by

XRD. The original hexagonal

columnar periodic array con-

tains the backfolded structural

defects. Heating this hexagonal

columnar LC into the isotropic

state followed by slow cooling

self-repairs these defects and

produces the structure shown in

the right side of Figure 7. As re-

ported in Table 1, below the F_h

Figure 7. ¹H,¹H DQ spinning sideband patterns of the polycyclic aromatic core (pyrene/naphthalene) of

and F_r-cphases there is

a

A

G

U

higher order phase which ex-

hibits intracolumnar order. In

G

ACHTREUNG

AHCTREUNG

all cases the higher order phase

is also pyramidal hexagonal or

ACHTREUNG

rectangular. Preliminary struc-

tural analysis by XRD experi-

properties of the pyrene and naphthalene rings in the liquid

crystalline phase of (3,4,5)12F8G1-2EOPy and (3,4,5)12G1-

2EONp as compared to (3,4,5)12F8G1-BuPy. A detailed un-

ments suggest that the higher order phase must mediate

even higher charge carrier mobilities than the F_hand F_r-c

phases reported previously for these compounds.^[8b]

A

ACHTREUNG

AHCTREUNG

derstanding of the molecular

dynamics of the polycyclic aro-

matic cores is helpful for de-

signing intracolumnar ordered

and stable stable columnar as-

semblies which exhibit promis-

ing charge carrier mobilities.

Molecular model: A simplified

molecular model of this self-as-

sembly process is illustrated in

Figure 8. For simplicity, the aro-

matic part of the dendron is

shown in red, the electroactive

donor in yellow, the alkyl semi-

fuorinated groups in blue and

the spacer in black. Also, for

simplicity and better visualiza-

tion in this Figure the dendrons

are not tilted. The preassembly

process that includes the back-

folded structural defects gener-

ated from the undesirable pack-

ing of the dendron and aromat-

ic donor shown in brown is il-

lustrated on top of the middle

column from the left side. Pre-

assembly is followed by the

self-assembly of the supramo-

lecular columns that self-organ- Figure 8. Schematic model of the self-assembly process.

Chem. Eur. J. 2006, 12, 6298 – 6314

ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

6309

V. Percec et al.

[2-(carbazol-9-yl)ethoxy]ethanol (19),^[15]4-(dimethylamino)pyridinium p-

toluenesulfonate (DPTS),^[25]2-{2-[2-(2-benzylethoxy)ethoxy]ethoxy}-p-

toluene sulfonate (9)^[13]and 3,5-(dipyrrolidine-1-yl)phenol (4)^[11]were

synthesized according to literature procedures. The synthesis of {2-[2-

(carbazol-9-yl)ethoxy]ethyl}3,4,5-tris-(12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,

Conclusion

The results reported herein have demonstrated that the at-

tachment of electron-donor groups to a semifluorinated

first-generation dendron or minidendron mediates the self-

assembly of the donor groups in a p-stack located in the

centre of supramolecular helical pyramidal columns. The

helical supramolecular columns self-organize into various

columnar liquid crystal phases able to enhance the charge

carrier mobility of the donor groups from that of the corre-

sponding molecules in amorphous state.^[8b]The use of vari-

ous electron-donors, spacers and first-generation semifluori-

nated dendrons has shown that this concept is general. The

results reported here are expected to impact the field of su-

pramolecular electronics. In addition they demonstrate that

the pyramidal liquid crystal phase is, most probably, more

general than previously considered.^[27]It also demonstrates

the utility of the fluorophobic effect or fluorous pha-

se^{[8b,9b,10,28]}in the self-assembly of new classes of pyramidal

liquid crystals.^[29]Structural analysis data suggest that the

higher order phases particularly those exhibiting a higher in-

tracolumnar order^[30]than the conventional columnar LC

phases are expected to display even higher charge carrier

mobilities than those reported previously for the same

donor groups in columnar LC phases.^[8b]Both the helicity

and the intracolumnar order of these supramolecular col-

umns resemble those encountered in supramolecular porous

assemblies.^[30]The helical pyramidal columnar assemblies ex-

hibiting intracolumnar order play a major role in the struc-

tural origin of functions.^[8b,30]Research on the elucidation of

the principles via which helical supramolecular columns

with intracolumnar order are generated is in progress.

5,5-heptadecafluoro-n-dodecan-1-yloxy)benzoate

(D8), {2-[2-((1-naphthyl)acetoxy)ethoxy]ethyl}3,4,5-tris(12,12,12,11,11,

10,10,9,9,8,8,7-,7,6,6,5,5-heptadecafluoro-n-dodecan-1-yloxy)benzoate

(3,4,5)12F8G1-2EONp (D4), {2-[2-((1-pyrenyl)acetoxy)ethoxy]eth-

yl}3,4,5-tris-(12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadecafluoro-n-do-

decan-1-yloxy)benzoate (3,4,5)12F8G1-2EOPy (D7) and [4-(1-pyrenyl)-

butyl]3,4,5-tris-(12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-hepta-decafluoro-

A

AHCTREUNG

n-dodecan-1-yloxy)benzoate (3,4,5)12F8G1-BuPy (D6) has been descri-

N

bed previously.^[8b]All other conventional materials and solvents were

commercially available and were used without further purification.

Techniques: ¹H (500 MHz) and ¹³C (125 MHz) NMR spectra in solution

were recorded on a Bruker DRX-500. Chromatographic purifications

were conducted using 200–400 mesh silica gel obtained from Natland In-

ternational Corporation, Morrisville, NC. The solid-state ¹H NMR ex-

periments were performed on a Bruker DRX spectrometer at a ¹H

Larmor frequency of 700 MHz (corresponding to a static magnetic field

of 16.4 Tesla). Fast magic-angle spinning (MAS) was applied at a fre-

quency of 30 kHz, using MAS rotors with 2.5 mm outer diameter. The

sample temperature was varied between 30 and 1108C and calibrated,

under these fast MAS conditions, following the procedure given in refer-

ence [26]. Thin-layer chromatography (TLC) was performed on pre-

coated TLC plates (silica gel with F₂₅₄indicator; layer thickness, 200 mm;

particle size, 5–25 mm; pore size, 60 , Sigma-Aldrich). Melting points

were measured using

a uni-melt capillary melting point apparatus

(Arthur H. Thomas Company, Philadelphia, USA) and are uncorrected.

High pressure liquid chromatography (HPLC) experiments were per-

formed with a Perkin-Elmer Series 10 GPC equipped with a LC-100

column oven (408C), Nelson Analytical 900 Series integrator data sta-

tion, and two Polymer Laboratories PL gel columns of 510²and 10⁴,

and THF as eluent at 1 mLmin^ꢀ1. Detection was by UV absorbance at

254 nm. Thermal transitions were measured on a TA Instruments 2920

modulated differential scanning calorimeter (DSC). In all cases the heat-

ing and cooling rates were 108Cmin^ꢀ1. First order transitions were re-

ported as the maxima or minima of the endothermic and exothermic

peaks during the second heating and cooling scans. X-ray diffraction ex-

periments were performed with Cu_Ka1radiation from a rotating anode

(Nonius FR591) X-ray generator and a multi-wire area detector (Sie-

mens). The Cu radiation was collimated and focused with a mirror-mono-

chromator optics. The X-ray beam path is maintained in low vacuum to

reduce the background scattering from air. Un-oriented powder samples

were kept in a temperature-controlled (ꢁ 0.18C) oven. Oriented fibers

were obtained by extruding the material in the liquid crystalline phase

with a mini extruder with a hole diameter of 0.5 or 0.7 mm. Density

measurements were carried out by flotation experiments in gradient col-

umns at 208C.^[9a,d,f]An Olympus BX-40 optical polarized microscope

(100magnification) equipped with a Mettler FP 82 hot stage and a Met-

tler FP 80 central processor was used to verify thermal transitions and to

characterize the anisotropic textures. MALDI-TOF mass spectra were re-

corded on a PerSpective Biosystems Voyager DE using 2-(4-hydroxyphe-

nylazo)benzoic acid as matrix. Angiotensin I and des-Arg1-Bradykinin

were used as standards. Sample preparation was as follows. The matrix

(10 mg) was dissolved in 1 mL of THF. The sample (10 mg) was also dis-

solved in 1 mL of THF. The matrix solution (50 mL) and the sample solu-

tion (10 mL) were mixed. To the mixture, 10 mL of the THF solution of

AgTFA (1 mgmL^ꢀ1) was added. The mixture (5 mL) was loaded on a

MALDI plate, and air dried before inserting into the vacuum chamber of

the MALDI instrument. High resolution mass spectra were run by direct

sample introduction on a LCMS (Micromass) platform (electron spray

ionizer, electron energy 70 eV). The elemental analysis (C, H) were per-

formed by M-H-W Laboratories, Phoenix, AZ, USA.

Experimental Section

Materials: 3,5-Dimethoxyphenol (1; 98%), 1-ethoxynaphthalene (13;

97%), methyl 3,4,5-trihydroxybenzoate (17; 98%), DCC (99%), 2,3-di-

hydropyran (97%), a,a,a-trifluorotoluene (99%), p-toluene sulfonic acid

(PTSA) (98%), tricaprylylmethylammonium chloride (Aliquat 336),

LiAlH₄(95%), 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113), diethy-

lene glycol (98%), 2-(2-chloroethoxy)ethanol (2; 99%), pyrrolidine, BH₃

(1m solution in THF), (all from Aldrich), perfluorooctyl iodide (>98%,

Fluka), 1,8-octadiene (14), triphenylphosphine, hydrobromic acid (48%),

benzyl bromide, tosyl chloride, sodium hydride (60% in mineral oil), 3,5-

dimethoxyphenol (97%), K₂CO₃, KOH, MeOH, EtOH, HCl (Fischer),

10% Pd/C and PdCl₂(97%, Lancaster) were used as received. DMF

(ACS reagent, Fisher Scientific) was dried over CaH₂and distilled under

vacuum. Et₂O, Bu₂O and THF (ACS reagent, Fisher Scientific) were

dried over sodium/benzophenone nd distilled. Et₃N was dried over CaH₂.

CH₂Cl₂was distilled from CaH₂. Hexanes (ACS reagent, Fisher Scientif-

ic) used for the Pd⁰-catalyzed coupling of perfluorooctyl iodide was

washed three times with concentrated H₂SO₄, three times with H₂O, 10%

Na₂CO₃and with H₂O and dried over anhydrous MgSO₄and finally dis-

tilled over sodium before use. Carbazole (10, 98%, Fluka) was recrystal-

lized twice from THF. Phenothiazine (6, 98%, Aldrich) was dissolved in

Et₂O to filter off green oxidation products before recrystallization from

EtOH

and

subsequent

sublimation.

3,4,5-Tris-(12,12,12,

2-[2-(3,5-Dimethoxyphenyl)ethoxy]ethanol (3): 3,5-Dimethoxyphenol (1;

2.5 g, 0.016 mol), K₂CO₃(6 g), KI (0.1 g) and 2-(2-chloroethoxy)ethanol

(2; 1.77 g, 0.016 mol) were added to a round bottom flask containing

DMF (50 mL). The mixture was heated at 808C for 16 h. The mixture

11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadecafluoro-n-dodecyloxy)benzoic acid

(12),^[10a]1-bromo-12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadecafluoro-

n-dodecane (2),^[10a]2-[2-(2-chloroethoxy)ethoxy]tetrahydropyran (7),^[24]2-

6310

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ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2006, 12, 6298 – 6314

Semifluorinated Dendrons

FULL PAPER

was poured into H₂O (100 mL) and extracted with Et₂O (350 mL). The

Et₂O layer was washed with 10% HCl (1100 mL), dried with MgSO₄

and concentrated. The crude material was passed through short silica gel

column, using Et₂O as eluent. Evaporation of the solvent gave the title

compound as brown oil (2.2 g, 56.8%). Purity (HPLC): 99+ %; R_f=0.38

(silica gel; Et₂O); ¹H NMR (CDCl₃, 500 MHz, 208C): d = 6.1 (s, 3H;

208C): d = 8.08 (m, 2H; ArH), 7.46 (m, 4H; ArH), 7.23 (m, 2H; ArH),

4.51 (t, ³J

A

N

3

CH₂), 3.66 (t, J(H,H)=4.7 Hz, 2H; CH₂), 3.53 (m, 10H; overlap 5CH₂),

A

2.2 (brs, 1H, OH); ¹³C NMR (CDCl₃, 125 MHz, 208C): d = 141.0, 126.0,

123.3, 120.6, 119.4, 109.3, 72.8, 71.4, 71.0, 70.9, 70.7, 69.7, 62.1, 43.5; CI-

MS: cacldc for C₂₀H₂₅NO₄: 343.4228 ; found: 344.1875 [M+H⁺].

ArH), 4.1 (t, ³J

3.75 (m, 8H; overlap OCH₃and CH₂), 3.66 (t, ³J

CH₂), 2.35 (brs, 1H; OH); ¹³C NMR (CDCl₃, 125 MHz, 208C): d

ACHTREUNG

3,5-Dimethoxyphenyl-3,4,5-tris(12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-hep-

AHCTREUNG

tadecafluoro-n-dodecan-1-yloxy)benzoate

[(3,4,5)12F8G1-2EODMB]

=

(D1): A mixture of 12 (0.4 g, 0.25 mmol), 3 (60 mg, 0.25 mmol), DCC

(160 mg) and DPTS (0.1 mg) was dissolved in a,a,a-trifluorotoluene

(6 mL) and stirred under N₂at 558C for 16 h. After cooling down to

258C, the salts were filtered and the solution precipitated into MeOH.

TLC indicated complete conversion. The crude product was precipitated

for five times from CH₂Cl₂into MeOH, then dried in the vacuum oven

at 258C for 24 h to yield the title compound (0.32 g, 70.5%). Purity

(HPLC): 99+ %; R_f=0.48 (silica gel; EtOAc/hexanes 30:70); ¹H NMR

161.9, 160.9, 94.7, 94.0, 93.8, 73.0, 70.0, 67.8, 67.5, 62.1, 55.7, 55.6; MS:

m/z: calcd for C₁₂H₁₈O₅: 242.2719; found: 265.1048 [M+Na⁺].

2-{2-[3,5-(Dipyrrolidin-1-yl)phenyl]ethoxy}ethanol (5): Compound

4

(1.26 g, 0.01 mol), K₂CO₃(5 g), KI (0.1 g) and 2-(2-chloroethoxy)ethanol

(2; 1.3 g, 10.5 mmol) were added to a round bottom flask containing of

DMF (40 mL). The reaction mixture was heated at 808C for 24 h. The

progress of the reaction was monitored by TLC, which showed complete

reaction. The reaction mixture was poured into H₂O (100 mL) and ex-

tracted with Et₂O (350 mL). The Et₂O layer was washed with 10%

HCl, dried with MgSO₄and concentrated. The crude material was passed

through short column of silica gel using Et₂O as eluent. The fractions

containing the product were collected and the solvent was evaporated to

produce the title compound (0.8 g, 25.0%) as a brown oil which solidify

upon standing. Purity (HPLC): 99+ %; m.p. 718C; R_f=0.41 (silica gel;

Et₂O); ¹H NMR (CDCl₃, 500 MHz, 208C): d = 5.58 (s, 2H; ArHortho

(CDCl₃, 500 MHz, 208C): d = 7.1 (s, 2H; ArH), 6.1 (s, 3H; ArH), 4.5 (t,

3

³J

A

(H,H)=4.70 Hz, 2H; CH₂), 4.0 (m,

3

6H; overlapped 3CH₂), 3.9 (t, J(H,H)=5.97 Hz, 4H; 2CH₂), 3.7 (s, 6H;

2OCH₃), 2.2–2.1 (m, 6H; 3CH₂), 1.8 (m, 12H; overlapped 6CH₂);

¹³C NMR (CDCl₃, 125 MHz, 208C): d = 166.5, 161.9, 160.9, 152.9, 142.4,

125.6, 120.5–108.2 (several CF multiplets), 108.6, 94.0, 93.5, 73.0, 70.0,

69.8, 68.8, 67.9, 64.5, 55.7, 31.9 (t, J_CF=22 Hz), 30.1, 29.1, 17.7, 17.4;

MALDI-TOF: m/z: calcd for C₅₅H₄₃F₅₁O₉: 1816.8596; found: 1839.6

[M+Na⁺]; elemental analysis calcd (%) for C₅₅H₄₃F₅₁O₉: C 36.36, H 2.39;

found: C 36.30, H 2.33.

to OCH₂CH₂), 5.40 (s, 1H; ortho to NR₂), 4.15 (t, ³J

ArOCH₂CH₂), 3.85 (t, ³J

(H,H)=4.7 Hz, 2H; CH₂), 3.72 (m, 2H; CH₂),

A

AHCTREUNG

3.67 (m, 2H; CH₂), 3.26 (m, 8H; 4CH₂N), 2.23 (m, 1H; OH), 1.95 (m,

8H; 4CH₂CH₂N); ¹³C NMR (CDCl₃, 125 MHz, 208C): d = 161.1, 150.3,

89.6, 88.0, 72.9, 70.4, 67.6, 62.3, 48.2, 25.9; MS: m/z: calcd for

C₁₈H₂₈N₂O₃: 320.4319; found: 321.219 [M+H⁺].

3,5-(Dipyrrolidin-1-yl)phenyl-3,4,5-tris(12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,

5,5-heptadecafluoro-n-dodecan-1-yloxy)benzoate

[(3,4,5)12F8G1-

(100 mg,

2EODPB] (D2): mixture of 12 (0.40 g, 0.25 mmol),

A

5

0.25 mmol), DCC (160 mg) and DPTS (0.10 mg) was dissolved in a,a,a-

trifluorotoluene (6 mL) and stirred under N₂at 558C for 16 h. After cool-

ing down to 258C, the salts were filtered and the solution precipitated

into MeOH. TLC indicated complete conversion. The crude product was

precipitated for five times from CH₂Cl₂into MeOH, then dried in the

vacuum oven at 258C for 24 h to yield the title compound (0.40 g, 84%).

Purity (HPLC): 99+ %; R_f=0.70 (silica gel; EtOAc/hexanes 30:70);

¹H NMR (CDCl₃, 500 MHz, 208C): d = 7.2 (s, 2H; ArH), 5.6 (s, 2H;

2-(2-Phenothiazine-10-yl-ethoxy)ethanol (8): Compound 8 was prepared

using

a 6 (3.8 g,

modified literature procedure.^[12]Phenothiazine

19 mmol) and NaH (1.5 g, 37.5 mmol; 60% suspension in mineral oil)

were added to of dry, freshly distilled dibutyl ether (30 mL). The mixture

was heated at 1358C for 60 min under N₂. 2-[2-(2-Chloroethoxy)ethoxy]-

tetrahydropyran (7)^[24](8.0 g, 38 mmol) and NaI (0.1 g) were added and

the reaction mixture was stirred for 48 h under N₂. The reaction mixture

was poured into H₂O (100 mL). A precipitate formed upon cooling at

08C, which was filtered, washed with water and dried. The crude product

was used on the next step without further purification. To a solution of

the crude product obtained from the previous step in MeOH (150 mL)

was added 10 mL of 10% HCl. The reaction mixture was heated under

reflux for 45 min. The mixture was poured into water (20 mL) and neu-

tralized with K₂CO₃. The product was extracted with Et₂O and the organ-

ic phase was washed with H₂O, dried with MgSO₄and evaporated. The

residue was further purified by column chromatography (silica gel,

EtOAc/hexanes 1:1) to yield the title compound as a viscous oil (2.9 g,

53%). Purity (HPLC): 99+ %; R_f=0.57 (silica gel; EtOAc/hexanes

60:40); ¹H NMR (CDCl₃, 500 MHz, 208C): d = 7.1 (m, 4H; ArH), 6.9

ArH), 5.4 (s, 1H; ArH), 4.5 (t, ³J

(H,H)=4.70 Hz, 2H; CH₂), 4.0 (m, 6H; overlapped 3CH₂), 3.9 (t, ³J-

(H,H)=4.70 Hz, 4H; 2CH₂), 3.2 (m, 8H; overlapped 4CH₂), 2.2–2.1 (m,

A

AHCTREUNG

6H; overlapped 3CH₂), 1.9 (m, 8H; overlapped 4CH₂), 1.8 (m, 12H;

overlapped 6CH₂); ¹³C NMR (CDCl₃, 125 MHz, 208C): d = 166.5, 161.9,

160.9, 152.9, 142.4, 125.6, 120.5–108.2 (several CF multiplets), 108.6, 94.0,

93.5, 73.0, 70.0, 69.8, 68.8, 67.9, 64.5, 55.7, 31.9 (t, J_CF=22 Hz), 30.1, 29.1,

17.7, 17.4; MALDI-TOF: m/z: calcd for C₆₁H₅₃F₅₁N₂O₇: 1895.019; found:

1895.1 [M+H⁺]; elemental analysis calcd (%) for C₆₂H₅₇F₅₁N₂O₇: C

38.97, H 3.01; found: C 38.91, H 3.09.

1-Naphthylethyl-3,4,5-tris(12,12,12,11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptade-

cafluoro-n-dodecan-1-yloxy)benzoate [(3,4,5)12F8G1-EtNp] (D3): DCC

(m, 4H; ArH), 4.1 (t, ³J

4.7 Hz, 2H; CH₂), 3.7 (t, ³J

A

ACHTREUNG

(300 mg, 1.5 mmol) was added under N₂to

a solution of 12 (1 g,

A

ACHTREUNG

0.63 mmol), 13 (0.13 g, 0.75 mmol), and DPTS (50 mg, 0.17 mmol) in

a,a,a-trifluorotoluene (15 mL), and the reaction mixture was stirred at

458C for 24 h. The mixture was diluted with CH₂Cl₂and precipitated in

MeOH four times. The crude product was purified by flash column chro-

matography (silica gel, CH₂Cl₂) and precipitated in EtOH from CH₂Cl₂

solution to yield the title compound as white solid (0.82 g, 75%). Purity

4.7 Hz, 2H; CH₂), 2.0 (brs, 1H; OH); ¹³C NMR (CDCl₃, 125 MHz,

208C): d = 145.5, 128.0, 127.7, 125.6, 123.2, 115.9, 72.7, 68.4, 62.2, 47.9;

MS: m/z: calcd for C₁₆H₁₇NO₂S: 287.3825 ; found: 310.0868 [M ⁺] . The

NMR data was consistent with the literature.^[12]

2-{2-[2-(2-Carbazol-9-yl-ethoxy)ethoxy]ethoxy}ethanol (11): Carbazole 10

(0.41 g, 2.44 mmol) was added to a suspension of NaH (1 g, 60% in min-

eral oil) in dry DMF (20 mL). 2-{2-[2-(2-Benzylethoxy)ethoxy]ethoxy}-

ethyl p-toluene-sulfonate (9) (1.0 g, 2.44 mmol) was added and the mix-

ture was stirred at 508C for 3 h under N₂, after which TLC indicated

complete reaction. The mixture was poured (carefully) to water (30 mL).

The resulting precipitate was filtered off, dried and used in the next step

without further purification. To a solution of the crude product obtained

from the previous reaction in EtOH (40 mL) was added Pd/C (0.5 g) cat-

alyst and the mixture was stirred in a hydrogen atmosphere for 24 h at

room temperature. The solution was filtered through Celite. Evaporation

of the solvent yielded 11 of as a viscous oil (0.2 g, 24%). Purity (HPLC):

99+ %; R_f=0.3 (EtOAc/hexanes 6:4); ¹H NMR (CDCl₃, 500 MHz,

(HPLC): 99+ %; R_f=0.74 (silica gel; EtOAc/hexanes 30:70); ¹H NMR

3

(CDCl₃, 500 MHz, 208C): d = 8.18 (d, J

A

(d, ³J

ArH), 7.43 (m, 2H; ArH), 7.19 (s, 2H; ArH), 4.67 (t, ³J

2H; CH₂), 4.01 (m, 6H; overlapped 3CH₂), 3.69 (m, 4H; 2CH₂), 3.54 (t,

³J

(H,H)=4.4 Hz, 2H, CH₂), 2.18–2.13 (m, 6H; 3CH₂), 1.9–1.8 (m, 12H,

ACHTREUNG

AHCTREUNG

6CH₂); ¹³C NMR (CDCl₃, 90 MHz, 208C): d=166.2, 152.4, 141.6, 133.9,

133.8, 132.1, 128.9, 127.5, 127.1, 126.2, 125.7, 125.3, 123.7, 120.5–108.2

(several CF multiplets), 107.8, 72.6, 68.3, 65.2, 30.8 (t, J_CF=22 Hz), 29.9,

28.9, 17.5, 17.3; MALDI-TOF: m/z: calcd for C₅₅H₃₇F₅₁O₅: 1746.8143 ;

found: 1770.8 [M+Na⁺]; elemental analysis calcd (%) for C₅₅H₃₇F₅₁O₅: C

37.82, H 2.13; found: C 37.77, H 2.21.

Chem. Eur. J. 2006, 12, 6298 – 6314

ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

6311

V. Percec et al.

{2-[2-(Phenothiazine-10-yl)ethoxy]ethyl}-3,4,5-tris(12,12,12,11„11,10,10,

9,9,8,8,7,7,6,6,5,5-heptadecafluoro-n-dodecan-1-yloxy)benzoate

dissolved in dry THF (200 mL). This solution was added drop-wise to

LiAlH₄(2.7 g, 0.14 mol) in dry THF (400 mL) at 08C and stirred for 3 h.

¹H NMR indicated complete conversion. The excess of LiAlH₄was

quenched by slow addition of a 9:1 mixture of THF and water, followed

by 10% NaOH (10 mL). The precipitate was filtered off, washed with

THF and the combined filtrates were concentrated. To the resulting resi-

due were added of 48% HBr (80 mL) and Aliquat-336 (1.1 g) and the

mixture was heated under reflux for 12 h. The reaction was cooled to

room temperature and extracted with Et₂O (3100 mL). The combined

ethereal solution was washed successively with H₂O (2100 mL), saturat-

ed NaHCO₃solution (1100 mL) and brine (1100 mL). The organic

phase was dried with MgSO₄and the solvent was distilled off. The crude

product was dissolved in Freon-113 and filtered over a short silica

column. Evaporation of the solvent produced 7 as a white waxy solid

(12.5 g, 44.7% overall yield). M.p. 338C: purity (HPLC): 99+ %; R_f=

[(3,4,5)12F8G1-2EOPt] (D5): A mixture containing 12 (1.0 g, 0.63 mmol)

and 8 (0.18 g, 0.63 mmol) was dissolved in a,a,a-trifluorotoluene (10 mL)

under N₂. DCC (0.388 g, 1.88 mmol) and DPTS (9 mg, 0.03 mmol) were

added and the reaction mixture was stirred at 558C for 72 h under N₂.

The progress of the reaction was monitored by TLC. The organic solu-

tion was concentrated and precipitated in MeOH. The crude product was

purified by silica gel column chromatography using CH₂Cl₂/EtOAc 3:1 to

yield the title compound as white crystals (0.66 g, 57%). Purity (HPLC):

99+ %; R_f=0.45 (silica gel; EtOAc/hexanes 30:70); ¹H NMR (CDCl₃,

500 MHz, 208C): d = 7.1 (m, 4H; ArH), 6.9 (m, 4H; ArH), 4.5 (t, ³J-

A

ACHTREUNG

3

6H; 3CH₂), 3.9 (t, J

ACHTREUNG

2H; CH₂), 2.2–2.1 (m, 6H; 3CH₂), 1.8 (m, 12H, overlapped 6CH₂);

¹³C NMR (CDCl₃, 125 MHz, 208C): d = 166.5, 152.9, 145.6, 142.2, 128.1,

127.8, 125.5, 125.2, 123.2, 120.5–108.2 (several CF multiplets), 115.6,

108.9, 73.1, 69.8, 68.8, 64.5, 43.3, 30.6 (t, J_CF=22 Hz), 30.1, 29.1, 17.7,

17.4; MALDI-TOF: m/z: calcd for C₅₉H₄₂F₅₁NO₆S: 1861.9701; found:

1862.7 [M+H⁺], 1885.7 [M+Na⁺], 1901.8 [M+K⁺]; elemental anal-

ysis calcd (%) for C₅₉H₄₂F₅₁NO₆S: C 38.06, H 2.27; found: C 37.95,

H 2.32.

1

0.83 (silica gel; Freon-113); H NMR (CDCl₃, 500 MHz, 208C): d = 3.41

(t, ³J

(H,H)=6.81 Hz, 2H; CH₂Br), 2.05 (m, 2H; CH₂CF₂), 1.86 (m, 2H;

G

CH₂), 1.59 (m, 2H; CH₂), 1.45–1.33 (m, 8H; overlap of 4CH₂); ¹³C NMR

(CDCl₃, 125 MHz, 208C): d = 34.2, 33.1, 31.3 (t, J_CF=22.1 Hz), 29.42,

29.38, 28.9, 28.4, 20.5; elemental analysis calcd (%) for C₁₆H₁₆BrF₁₇: C

31.44, H 2.64; found: C 31.44, H 2.64.

Methyl 3,4,5-tris-(16,16,16,15,15,14,14,13,13,12,12,11,11,10,10,9,9-heptade-

2-{2-[2-(2-Carbazol-9-yl-ethoxy)ethoxy]ethoxy}ethyl-3,4,5-tris-(12,12,12,

11,11,10,10,9,9,8,8,7,7,6,6,5,5-heptadecafluoro-n-dodecan-1-yloxy)ben-

zoate [(3,4,5)12F8G1-4EOCz] (D10): DCC (300 mg, 1.5 mmol) was

cafluoro-n-hexadec-1-yloxy) benzoate [(3,4,5)16F8G1-CO₂Me]: In

a

three-neck round-bottom flask equipped with a condenser, Ar inlet-

outlet and a magnetic stirrer, a mixture of K₂CO₃(9 g, 4 equiv) and DMF

(150 mL) was thoroughly bubbled with Ar for 0.5 h to eliminate air.

Methyl 3,4,5-trihydroxybenzoate (1.2 g, 6.55 mmol) was added and the

mixture was heated to 808C. 1-Bromo-16,16,16,15,15,14,14,13,13,12,12,

11,11,10,10,9,9-heptadecafluoro-n-hexadecane (16; 12 g, 19.6 mmol) was

added and the mixture was stirred under Ar atmosphere at 808C for

12 h. TLC analysis showed complete reaction. The reaction mixture was

cooled to room temperature and poured into 100 mL of water. The prod-

uct was extracted with Et₂O (2100 mL). The combined ethereal solu-

tion was washed successively with water, 10% HCl, saturated NaHCO₃

and brine. The ethereal solution was dried over MgSO₄. The solvent was

fully evaporated and the product was recrystallized fro acetone to pro-

duce white crystals (4.8 g, 41%). M.p. 878C; purity (HPLC): 99+ %;

R_f=0.80 (EtOAc/hexanes 3:7); ¹H NMR (CDCl₃, 500 MHz, 208C): d =

added under N₂to

a solution of 12 (0.51 g, 0.64 mmol), 11 (0.1 g,

0.64 mmol), and DPTS (50 mg, 0.17 mmol) in a,a,a-trifluorotoluene

(8 mL), and the reaction mixture was stirred at 558C for 24 h. The reac-

tion mixture was filtered off to remove insoluble salts. The filtrate solu-

tion was concentrate under vacuum and the crude product was precipitat-

ed by the addition of methanol (20 mL). The crude product was purified

by silica gel column chromatography using CH₂Cl₂/EtOAc 3:1 to yield

the title compound as a sticky white solid (0.6 g, 49%). Purity (HPLC):

99+ %; R_f=0.36 (silica gel; EtOAc/hexanes 2:3); ¹H NMR (CDCl₃,

500 MHz, 208C): d = 8.1 (d, ³J

ArH), 7.2 (m, 6H; ArH), 4.5 (t, ³J

(H,H)=5.97 Hz, 2H, CH₂), 4.2–4.0 (m, 6H; 3CH₂), 3.86 (t, ³J

4.70 Hz, 2H; CH₂), 3.7 (t, ³J

(H,H)=5.97 Hz, 2H; CH₂), 3.54 (m, 2H;

ACHTREUNG

AHCTREUNG

A

ACHTREUNG

AHCTREUNG

7.29 (s, 2H; ArH), 4.05 (t, ³J

(H,H)=4.7 Hz, 6H; 3OCH₂), 3.91 (s, 3H;

A

CH₂), 3.49 (m, 6H; 3CH₂), 2.3–2.1 (m, 6H; 3CH₂), 1.8 (m, 12H; overlap-

ped 6CH₂); ¹³C NMR (CDCl₃, 125 MHz, 208C): d = 166.5, 152.9, 142.4,

141.0, 126.0, 125.7, 123.3, 120.6, 119.4, 120.5–108.2 (several CF multip-

lets), 109.3, 108.7, 73.0, 71.4, 71.0, 70.9, 69.7, 69.6, 68.9, 64.6, 43.6, 30.6 (t,

CO₂CH₃), 2.08 (m, 6H; 3CH₂), 1.85 (m, 4H; 2CH₂), 1.77 (m, 2H; CH₂),

1.62 (m, 6H; 3CH₂), 1.53 (m, 6H; 3CH₂), 1.40 (m, 18H; 9CH₂);

¹³C NMR (CDCl₃, 125 MHz, 208C): d =167.0, 153.2, 142.6, 125.7, 120.5–

108.2 (several CF multiplets), 108.5, 73.8, 69.5, 52.6, 30.6 (t, J_CF=22 Hz),

30.1, 29.71, 29.66, 29.61, 29.5, 26.4, 20.5; MALDI-TOF: m/z: calcd for

C₅₆H₅₃F₅₁O₅: 1774.9524; found: 1796.8 [M+Na]⁺.

J

_CF=22 Hz), 30.1, 29.1, 17.7, 17.5; MALDI-TOF: m/z: calcd for

C₆₃H₅₀F₅₁NO₈: 1918.0105; found: 1918.6 [M+H⁺], 1941.6 [M+Na⁺],

1957.7 [M+K⁺].

Oct-7-ene-1-ol (15): A 1m solution of BH₃·THF complex in THF (60 mL,

60 mmol) of was added under N₂at 08C to 1.8-octadiene 14 (22 g,

0.2 mol). The mixture was allowed to reach 258C and stirred at this tem-

perature for 1 h, then it was heated under reflux for 1 h. After cooling

down to 08C, a solution of NaOH (6 gs) in H₂O (30 mL), then 30%

H₂O₂(20 mL) were subsequently added drop-wise under stirring. The

temperature was raised to 258C and the mixture was stirred at the same

temperature for 12 h. The reaction mixture was poured into Et₂O

(150 mL). The ethereal solution was washed with H₂O (2100 mL). The

organic phase was dried over MgSO₄and the solvent was distilled off.

The resulting crude product was purified by vacuum distillation (b.p.

958C, 10 mbar) to give a colorless oil (7.7 g, 30%). ¹H NMR (CDCl₃,

500 MHz, 208C): d = 5.83 (m, 1H; CH₂=CHR), 5.01–4.92 (m, 2H; CH₂=

CHR), 3.63 (m, 2H; CH₂OH), 2.04 (m, 2H; CH₂=CHCH₂R), 1.55 (m,

6H; CH₂C2 and C5 positions), 1.35 (m, 6H; CH₂, C3 and C4 positions).

The NMR and other analytical data were consistent with the literature.^[1]

3,4,5-Tris-(16,16,16,15,15,14,14,13,13,12,12,11,11,10,10,9,9-heptadeca-

fluoro-n-hexadec-1-yloxy)benzoic acid [(3,4,5)16F8G1-CO₂H] (18):

A

20% KOH solution (10 mL) was added to a solution of (3,4,5)16F8G1-

AHCTREUNG

CO₂Me obtained on the previous step (3.5 g, 3.14 mmol) in EtOH

(60 mL). The mixture was heated under reflux for 4 h. TLC analysis

showed complete reaction. The solvent was fully evaporated and the re-

sulting potassium salt was dissolved in of THF/water 3:1 (70 mL). The

solution was acidified with 2m HCl until pH 4. Water (70 mL) was added

and the product was filtered, washed with water and methanol respec-

tively and dried. Recrystallization from acetone produced 18 as white

crystals (3.1 g; 90%). Purity (HPLC): 99+ %; R_f=0.63 (EtOAc/hexanes

3:7); ¹H NMR (CDCl₃, 500 MHz, 208C): d = 7.32 (s, 2H; ArH), 4.04 (t,

³J

(H,H)=4.7 Hz, 6H, 3OCH₂), 2.03 (m, 6H; 3CH₂), 1.85 (m, 4H;

G

2CH₂), 1.79 (m, 2H; CH₂), 1.68 (m, 6H; CH₂), 1.55 (m, 6H; 3CH₂), 1.49

(m, 18H; 9CH₂); ¹³C NMR (CDCl₃, 125 MHz, 208C): d = 171.6, 153.2,

143.6, 124.0, 120.5–108.2 (several CF multiplets), 108.9, 73.8, 69.4, 30.6 (t,

J

_CF=22 Hz), 30.1, 29.71, 29.66, 29.61, 29.5, 26.4, 20.5; elemental analysis

1-Bromo-16,16,16,15,15,14,14,13,13,12,12,11,11,10,10,9,9-heptadecafluoro-

calcd (%) for C₅₆H₅₃F₅₁O₅: C 37.89, H 3.01; found: C 37.89, H 3.01.

n-hexadecane (16):

To a degassed solution of 15 (5.92 g, 45.8 mmol) and perfluorooctyl

iodide (25 g, 45.8 mmol) in hexanes (300 mL) and Et₂O (100 mL) was

2-(2-Carbazol-9-yl-ethoxy)ethyl-3,4,5-tris-(16,16,16,15,15,14,14,13,13,

12,12,11,11,10,10,9,9-heptadecafluoro-n-hexadecan-1-yloxy)benzoate

[(3,4,5)16F8G1-2EOCz] (D9): DCC (140 mg, 0.68 mmol) was added

under N₂to a solution of 18 (0.4 g, 0.23 mmol), 19 (0.06 g, 0.23 mmol),

and DPTS (10 mg) in a,a,a-trifluorotoluene (6 mL), and the reaction

added [Pd(PPh₃)₄](3.5 g). The mixture was purged with N and stirred at

A

2

258C for 24 h. The catalyst was filtered off and washed with ether. The

combined ethereal solutions were concentrated and the residue was re-

6312

www.chemeurj.org

ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2006, 12, 6298 – 6314

Semifluorinated Dendrons

FULL PAPER

mixture was stirred at 558C for 24 h. The reaction mixture was filtered

off to remove insoluble salts. The filtrate solution was concentrate under

vacuum and the crude product was precipitated by the addition of metha-

nol (20 mL). The crude product was purified by silica gel column chroma-

tography using CH₂Cl₂/EtOAc 3:1 to yield the title compound as white

solid (0.35 g, 77%). Purity (HPLC): 99+ %; R_f=0.71 (silica gel; EtOAc/

locyanines 2000, 4, 88; d) N. Bodden, R. J. Bushby, J. Clements, B.

Movaghar, J. Mater. Chem. 2001, 9, 2081; e) F. Würthner, Angew.

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15, 1135.

hexanes 30:70); ¹H NMR (CDCl₃, 500 MHz, 208C): d

(H,H)=7.7 Hz, 2H; ArH), 7.4 (m, 4H; ArH), 7.2 (m, 6H, ArH), 4.5 (t,

³J(H,H)=5.9 Hz, 2H; CH₂), 4.4 (t, ³J

(H,H)=5.97 Hz, 2H; CH₂), 4.0 (m,

2H; CH₂), 3.9 (m, 6H; 3CH₂), 3.7 (t, J

=

8.1 (d, ³J-

ACHTREUNG

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A

ACHTREUNG

3

A

(m, 6H; 3CH₂), 1.8 (m, 6H; 3CH₂), 1.6 (m, 8H; 4CH₂), 1.4 (m, 8H;

overlapped 4CH₂), 1.3 (m, 16H, overlapped 8CH₂); ¹³C NMR (CDCl₃,

125 MHz, 208C): d = 166.7, 153.2, 142.8, 141.0, 126.1, 125.1, 123.3, 120.6,

119.5, 120.5–108.2 (several CF multiplets), 109.1, 108.5, 73.8, 69.8, 69.5,

43.7, 32.8, 31.4, 31.3, 31.1, 30.7, 29.8, 26.6, 20.5; elemental analysis calcd

(%) for C₇₂H₆₈F₅₁NO₆: C 42.98, H 3.41; found: C 42.98, H 3.41.

Acknowledgements

Financial support by the National Science Foundation (DMR-0102459

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Self-assembly of semifluorinated dendrons attached to electron-donor groups mediates their π-stacking via a helical pyramidal column

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