Perfluoroalkylation of Square-Planar Transition Metal Complexes: A Strategy to Assemble Them into Solid State Materials with a π-π Stacked Lamellar Structure

Article abstract of DOI:10.1021/acs.cgd.5b01291

Formation of π-π stacked lamellar structure is important for high performance organic semiconductor materials. We previously demonstrated that perfluoroalkylation of aromatics and heteroaromatics was one of the strategies to design organic crystalline materials with π-π stacked lamellar structures while improving air stability as a result of the strong electron withdrawing ability of perfluoroalkyl substituents. Square-planar transition metal complexes with large π-conjugated ligands are also an important category of semiconductor materials. We have perfluoroalkylated square-planar transition metal complexes, leading to the formation of a π-π stacked lamellar crystal packing motif in the solid state. Here we report six crystal structures of Pd and Pt complexes with bis-perfluorobutylated catechol ligand as one of the two ligands that bonds to the metal centers. This structural design possesses similar molecular topology when compared to perfluoroalkylated aromatics and heteroaromatics we have reported previously, again, demonstrating the steering power of the perfluoroalkyl substituents in engineering organic and organometallic solid state materials.

Full text of DOI:10.1021/acs.cgd.5b01291

Subscriber access provided by University of Otago Library
Article
Perfluoroalkylation of square-planar transition metal complexes: a strategy to
assemble them into solid state materials with a #-# stacked lamellar structure
Mohammad O BaniKhaled, John D Becker, Miles Koppang, and Haoran Sun
Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b01291 • Publication Date (Web): 08 Mar 2016
Downloaded from http://pubs.acs.org on March 15, 2016
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Crystal Growth & Design is published by the American Chemical Society. 1155
Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 35
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
Perfluoroalkylation of squareꢀplanar transition metal
complexes: a strategy to assemble them into solid
state materials with a π−π stacked lamellar structure
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Mohammad O. BaniKhaled, John D. Becker, Miles Koppang, and Haoran Sun*
Department of Chemistry, University of South Dakota, Vermillion, SD, USA, 57069
KEYWORDS. Perfluoroalkylation, Transition Metal Complex, π−π Interaction, Crystal
Structure, Fluorineꢀfluorine Interaction; Semiconductor, Electrochemistry, Redox Potential
ACS Paragon Plus Environment
1

Crystal Growth & Design
Page 2 of 35
1
2
3
4
5
6
7
8
9
ABSTRACT: Formation of π−π stacked lamellar structure is important for high performance
organic semiconductor materials. We previously demonstrated that perfluoroalkylation of
aromatics and heteroaromatics was one of the strategies to design organic crystalline materials
with π−π stacked lamellar structures while improving airꢀstability as a result of the strong
electron withdrawing ability of perfluoroalkyl substituents. Squareꢀplanar transition metal
complexes with large π−conjugated ligands are also an important category of semiconductor
materials. We have perfluoroalkylated squareꢀplanar transition metal complexes, leading to the
formation of π−π stacked lamellar crystal packing motif in the solid state. Here we report six
crystal structures of Pd and Pt complexes with bisperfluorobutylated catechol ligand as one of
the two ligands that bonds to the metal centers. This structural design possesses similar
molecular topology when compared to perfluoroalkylated aromatics and heteroaromatics we
have reported previously, again, demonstrating the steering power of the perfluoroalkyl
substituents in engineering organic and organometallic solid state materials.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment
2

Page 3 of 35
Crystal Growth & Design
1
2
3
4
1. Introduction
5
6
7
8
9
Controlling and modulating the structure solid state organic materials is a significant, yet
challenging, task faced by material scientists to reach the goal of “materials by design”.1ꢀ3 From
supramolecular chemistry to metalꢀorganicꢀframework (MOF)4 and, most recently, covalentꢀ
organicꢀframework (COF)5, researchers engage in activities that could potentially control and
modulate the solid state structure of organicꢀ and metalꢀorganic based functional materials.5ꢀ7 By
manipulating the coordination and covalent bonding within the threeꢀdimensional (3D) structure,
researchers have gained the ground to control and modulate the 3D solid state structure of MOF
and COF materials.7ꢀ9 On the other hand, many solid state functional materials are small chargeꢀ
neutral molecularꢀbased in which the 3D structure and the functions of these materials primarily
relies on nonꢀcovalent and nonꢀcoordinating weak intermolecular interactions,10ꢀ12 for example,
hydrogen bonding13, 14 and van der Waals interactions.12 Because the energy of these weak nonꢀ
covalent and nonꢀcoordinating interactions is estimated less than 10% of the bonding energy of a
typical covalent or coordinating bonds, modulating and controlling these weak interactions
through molecular design is paramount, yet tremendously challenging.15
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Recent work done by several groups8, 13, 14, 16ꢀ21 demonstrated the potential of utilizing nonꢀ
covalent bonding including halogen bonding17, 18, 22 for engineering solid state organic materials
and controlling organic reactions in the solid state.14, 19ꢀ21 Recently, we have demonstrated that
perfluoroalkylation of aromatics and heteroaromatics is capable of engineering organic
semiconductor materials with π−π stacked lamellar structures while improving airꢀstability.15, 23ꢀ
26 This dual improvement in this type of functional organic materials is mainly due to the strong
electron withdrawing ability of perfluoroalkyl substituents26 and multiple CꢀFꢀꢀꢀFꢀC attractive
intermolecular interactions between perfluoroalkyl chains15, 23, 27ꢀ30. The formation of the π−π
ACS Paragon Plus Environment
3

Crystal Growth & Design
Page 4 of 35
1
2
3
4
5
6
7
8
9
stacked lamellar structure is a key to improve the charge mobility for high performance organic
semiconductor devices.31ꢀ35 While aromatics with large π−conjugation are one type of
candidates for modern organic semiconductor materials,31, 32, 36, 37 the planar metal complexes
represent another candidate type for such applications.35, 38ꢀ43
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
One thing in common for both aromatic and metal complex based semiconductor materials is
that both are chargeꢀneutral molecular materials forming molecular crystals based upon attractive
weak nonꢀcovalent intermolecular interactions.8, 10, 44, 45 Thus based upon our previous results of
aromatic perfluoroalkylation assisting in the formation of lamellar π−π stacked solid structure of
23, 27
aromatics and heteromatics,15,
we hypothesize that planar metal complexes with
perfluoroalkylated ligand(s) and similar molecular topology are expected to form lamellar π−π
stacked solid state structures as well. To test our hypothesis, we synthesized squareꢀplanar
palladium and platinum complexes with bisperfluorobutylated catechol and various substituted
2,2’ꢀbipyridine ligands and a phenanthroline ligand (Chart 1). These compounds possess similar
molecular topology compared to our previously reported perfluorobutylated aromatics (Chart 2).
Here we report the synthesis and characterization of six new compounds and their crystal
structures. All of these six compounds are fourꢀcoordinating squareꢀplanar complexes that form
exclusively lamellar π−π stacked solid state structures even though some have substituents with
very large steric hindrance, for example, the tꢀbutyl group. This result provides a new pathway
to engineer solid state metal complex materials not only in the fields of semiconductor materials
but also optical materials in which solid state structure determines their function and
performance.
ACS Paragon Plus Environment
4

Page 5 of 35
Crystal Growth & Design
1
2
3
4
Chart 1. Compounds studied
5
6
7
R
O
O
C4F9
C4F9
N
N
O
O
C4F9
C4F9
N
N
8
9
Pd
M
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
R
M= Pd(II) R=
M= Pt(II) R=
H
Br
t-Bu
OMe
H
Compd 1
Compd 2
Compd 3
Compd 4
Compd 6
Compd 5
Chart 2. Comparison of molecular topology
F
F
F
F
F
F
F
F
F
F
F
F
F
S
S
F
O
O
F
N
N
N
N
F
F
F
F
Pd
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
1
7
Left: metal complex reported in this work; right: aromatic molecule reported previously23.
Both molecules form lamellar π−π stacked solid state structures with very similar interꢀplanar
distances.
2. Results and Discussion
2.1 Synthesis and Characterization
Our strategy for preparing squareꢀplanar transition metal complexes involves the use of
bidentate chelating aromatic ligands that possess perfluorobutyl substituents. To reach the
similar topology of our previously reported compound 7, and generate chargeꢀneutral complexes,
we chose 4,5ꢀbisperfluorobutyl catechol dianion as one ligand and 2,2’ꢀbipyridine as the other
ligand for the metal complexes. Pd(II) and Pt(II) metal ions were selected to form the
corresponding four coordinate squareꢀplanar metal complexes.
ACS Paragon Plus Environment
5

Crystal Growth & Design
Page 6 of 35
1
2
3
4
Scheme 1. Synthesis of bisperfluorobutylated catechol.
5
6
7
8
9
O
O
HO
OH
O
O
O
O
HO
OH
Br2
BBr3
CH3I/K2CO3
Cu, C4F9I
HFE7200, DMSO
CH2Cl2
67%
CH2Cl2
85%
DMF, 80 oC,12hr
84%
F9C4
C4F9
F9C4
C4F9
Br
Br
65%
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
8
9
10
11
Scheme 2. Synthesis of Pd(II) complexes.
R
R
R
R
R
R
CHCl3, MeOH, Et3N
PdCl2
N
N
N
N
CH3CN
N
N
Pd
HO
OH
Pd
25oC, 12hr
O
O
Cl Cl
R= H, Br, t-Bu, OMe
F9C4
C4F9
C4F9
F9C4
Bisperfluoroalkylated catechol was prepared through a fourꢀstep reaction pathway starting with
a diolꢀprotection step (Scheme 1). Methylation is often used for protecting catechol in organic
synthesis as it provides an efficient and inexpensive means for protecting diol functionality in a
multistep synthetic process.46 To a mixture of catechol and potassium carbonate in degassed
DMF solution, methyl iodide was added drop wise at 0 °C controlled by an ice bath. Then, the
reaction mixture was stirred at 80 °C for 12 hours to reach completion.47 One of the major
advantages of using this protection step in the synthetic process is avoiding the formation of Cu
complexes resulting from the subsequent perfluoroalkylation reaction.15 Bromination was
carried out using bromine in dichloromethane at 0 °C to yield the dibrominated compound 9 in
85 % yield. The brominated derivative was subjected to iodoperfluorobutane in the presence of
copper in dry DMSO and perfluorobutyl ethyl ether (HFEꢀ7200) at 135 °C to afford
bisperfluorobutylated compound 10 in 65 % yield. The deprotection step was accomplished by
ACS Paragon Plus Environment
6

Page 7 of 35
Crystal Growth & Design
1
2
3
4
5
6
treating compound 10 with boron tribromide dissolved in dichloromethane at 0 °C to afford
compound 11 as a yellow oil in 67 % yield.
7
8
9
The complexation of 2,2’ꢀbipyridine derivatives and 1,10ꢀphenanthroline with palladium
dichloride was carried out under dry N2 atmosphere in acetonitrile.48 The progress of the
reactions was monitored by TLC. The final complexation process in the reaction was proceeded
by adding compound 11 in methanol dropwise to the CHCl3/Methanol solution of bpyPd(II)Cl2
at room temperature followed by addition of triethylamine. Color change of the reaction mixture
was observed after about one hour for all the Pd complexes. The platinum complex was
prepared using a slightly modified synthetic procedure in which one equivalent of platinum
dichloride was added to a solution of 1.2 equivalents of the ligand and stirred for 12 hours at 100
°C. Both reactions proceeded in moderate to good yields. Expanding on this methodology, a
library of perfluoralkylated square planar of Pd and Pt complexes was prepared and subjected to
single crystal growth with slow evaporation method.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
All the compounds were then characterized by H, 19F NMR spectra, ESIꢀMS spectra,
elemental analysis, and xꢀray single crystal structure analysis. Detailed synthetic procedures,
characterization methods, and all characterization data are given in the supporting information.
ESIꢀMS spectra of these metal complexes give the molecular mass according to the isotope
natural abundance distribution and matches well with simulated MS results with the exact
1
isotope distribution pattern. It is also worth noting that the H NMR spectra of compound 6
show clear 195Ptꢀ1H coupling for proton signal at 9.17 ppm with a coupling constant of 29.52 Hz
(See supporting information). The chemical shift information of this signal together with the
coupling information clearly concludes this signal belongs to the ortho proton on the bipyridine
adjacent to the nitrogen atom.
ACS Paragon Plus Environment
7

Crystal Growth & Design
Page 8 of 35
1
2
3
4
2.2 Crystal Structure Characterizations
5
6
7
8
Single crystals suitable for xꢀray diffraction were obtained using slow evaporation method over
the period of a couple weeks to a couple months at room temperature in darkness. Long glass
tubes (30 to 60 cm long, ID 4 mm, OD 5mm) with a plastic cap (for example, caps for 5 mm
NMR tube) were used for crystal growing. More detailed experimental procedures are given in
the supporting information or in our previous publications27. Single crystal XRD data were
collected at 100 K using MoꢀKα radiation (λ = 0.71073 Å) on a Bruker CCD APEXII
diffractometer. Structures were solved by the Direct Method using SHELXLꢀ97 in conjunction
with standard differential Fourier transformation techniques and subsequently refined by fullꢀ
matrix leastꢀsquares analyses. All hydrogen atoms were placed in their ideal positions and all
nonꢀhydrogen atoms were refined anisotropically except for the cases where minor disorder was
observed on the terminal fluorine atoms of the perfluoroalkyl chains in compounds 1 and 6.
The quality of single crystal of compound 3 was not as good as single crystal for other
compounds. The reason for poor quality crystal might be very complicate, one thing in common
that we observed for this type pefluoroalkylated aromatics, heteroaromatics, and squareꢀplanar
metal complexes is they intend form long needle crystals if they form the π−π stacked solid state
structures. Though the longer dimension of such long needle crystals can be as long as couple
center meters, the short dimensions could be less than 100 micrometers. This very thin needle
crystal creates a challenging problem for xꢀray single crystal diffraction data collection.
Furthermore, the crystals were very fragile because they were formed with chargeꢀneutral
molecules, and the stability of the crystal structures relay only on weak nonꢀcovalent
interactions. For compound 3, we solved the main structure, but there were unsolved, likely,
solvent molecules in the crystal packing due the poor diffraction data and possibly disordered.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment
8

Page 9 of 35
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
Repetitive attempts to grow high quality crystal were yet still unsuccessful. The main frame of
the crystal structure of compound 3 should be in correct form though the distance measurement
error might be larger than other perfectlyꢀsolved structures. Detailed crystal structure refinement
data are listed in table 1 and the corresponding cif files are given in the supporting information.
Table 1. Summary of Crystallographic and Refinement Data for Compounds 1ꢀ6
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Compound
1
2
3
4
Formula
C24H10F18
N2O2Pd
C24H8Br2F18N2O2 C34H26F18N2O2Pd
C26H14F18N2O4Pd
Pd
formula wt
temp, K
806.74
100
964.54
100
918.95
100
866.79
100
cryst setting
space group
Hall symbol
tetragonal
Iꢀ42d
orthorhombic
F d d d
monoclinic
P21/c
triclinic
P ꢀ1
Iꢀ42bw
122
ꢀF 2uv 2vw
70
ꢀP2ybc
14
ꢀP 1
international
tables no.
2
a, Å
29.374
29.374
6.3995
90
6.3920
39.810
45.443
90
6.9281
28.342
18.780
90
7.8439
10.2745
18.498
87.522
86.574
78.561
2
b, Å
c, Å
α, deg
β, deg
γ, deg
Z
90
90
96.496
90
90
90
8
16
4
cell vol (Å3)
5521.5
1.941
11563.6
2.216
3664.0
1.666
1457.8
1.975
density
(diffrn), g cm−3
Absorb coeff,
mm−1
0.822
3.552
0.633
0.791
ACS Paragon Plus Environment
9

Crystal Growth & Design
Page 10 of 35
1
2
3
4
5
6
7
8
F(000)
data
(θmin−θmax),
deg
3136
7360
1872
848
range
1.386ꢀ25.422
1.360ꢀ26.480
1.307ꢀ22.486
2.21ꢀ28.78
9
index ranges
±35,±35,±7
9922
±8,±53,±61
9914
±7, ±30, ±20
9882
±10, ±13, ±24
9996
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
measured
reflns
Independent
reflns
2571
2479
3722
3396
4789
4329
6891
6329
reflns with I >
2σ(I)
max/min trans
0.960/0.921
1/194
0.837/0.718
0/222
0.892/0.931
0/496
0.931/0.892
0/460
restraints/para
ms
GOF
1.113
1.261
1.090
1.229
R
[F2
>
0.0565
0.0164
0.0691
0.0744
2σ(F2)]
wR (F2)
0.1636
0.0636
0.2014
0.2064
ACS Paragon Plus Environment
10

Page 11 of 35
Crystal Growth & Design
1
2
3
4
Table 1. Summary of Crystallographic and Refinement Data for Compounds 1ꢀ6 (continued)
5
6
7
8
9
Compound
Formula
5
6
C52H22F36N4O5Pd2 C24H10F18N2O2Pt
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
formula wt
temp, K
1679.54
100
895.43
100
cryst setting
space group
Hall symbol
monoclinic
C 2/c
tetragonal
Iꢀ4 2d
ꢀC 2yc
15
Iꢀ4 2bw
122
international
tables no.
a, Å
39.386
10.8745
12.9106
90.00
95.913
90.00
4
29.345
29.345
6.4395
90
b, Å
c, Å
α, deg
β, deg
γ, deg
Z
90
90
8
cell vol (Å3)
5500.2
2.028
5545
2.145
density (diffrn), g
cm−3
Absorb
mm−1
coeff,
0.831
5.210
F(000)
data
3272
3392
range
1.04ꢀ25.312
1.388ꢀ25.351
(θmin−θmax), deg
index ranges
±47, ±13, ±15
9966
±35,±35,±7
9117
measured reflns
Independent reflns
5012
2553
ACS Paragon Plus Environment
11

Crystal Growth & Design
Page 12 of 35
1
2
3
4
5
reflns with I >
2σ(I)
4570
2374
6
7
8
9
max/min trans
restraints/params
GOF
0.9365/0.6355
0/481
0.949/0.541
0/195
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1.103
1.082
R [F2 > 2σ(F2)]
wR (F2)
0.0262
0.0366
0.0960
0.0744
Overall, all these Pd and Pt metal complexes show four coordinate squareꢀplanar molecular
structures with some of them having distortions due to different substituents on the bipyridine
ring (via infra). There is no fifth ligand coordinated to the metal center although a water
molecule was involved in the crystal structure of compound 5. Compound 1 shows a perfect
square planar molecular structure for the coordinating center. As we expected from our previous
observation on perfluoroalkylated aromatics15, 23, 27, structure 1 display almost perfect lamellar
π−π stacked crystal packing motif as shown in Figure 1. The only imperfection is the angle
between two adjacent planes is 0.6 degree, the distance between Pd of one molecule to its
adjacent plane is 3.200 Å, and the average distance from one molecule to the plane of the other
molecule is 3.199 Å. Its nonꢀperfluoroalkylated analog shows locally π−π stacked lamellar
structure with interplanar distance of 3.233 Å, however, its entire solid state packing shows a
distorted lamellar packing motif towards Tꢀshape based herringbone packing motif.49 This
observation is dramatically amplified in its phenanthroline analog which has a Tꢀshape based
herringbone packing motif (via infra).50
ACS Paragon Plus Environment
12

Page 13 of 35
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. Molecular packing and interplanar distances of compound 1. Top left: top view of
adjacent two molecules in a π−π stacked molecular column; top right, side view of the same two
molecules in the left; bottom, view along aꢀaxis of a 2x2x2 crystal packing units.
Compared to our previously reported perfluoroalkylated aromatics (for example, compound 7)
with similar molecular topology, compound 1 possesses the smallest interplanar π−π distance
partially due to the Pd donor effect.51 In the same metal complex stack, Pd is not linearly
connected with each other, it shows an angle of 141 degree for the PdꢀPdꢀPd, indicating the
shortest distance is Pd−π interactions, not the Pd−Pd metalꢀmetal bonding. This observation is
similar to what was observed in Pd allyic complexes where the Pd dꢀorbitals overlap with the
π orbital of the allyic ligand.52, 53
Addition of large diameter bromine atoms onto the bipyridine ring further reduces the
interplanar distance of the π−π stacked column to an average of 3.196 Å, (from the 21 nonꢀ
ACS Paragon Plus Environment
13

Crystal Growth & Design
Page 14 of 35
1
2
3
4
5
6
7
8
9
hydrogen atom mean plane of the metal complex core) with shortest distance of 2.978 Å and
longest distance of 3.414 Å. Because of bromine atom’s high polarizability, it forms halogen
bonding with halogen atoms on adjacent molecules.17, 18, 54ꢀ62 Figure 2 clearly shows BrꢀꢀꢀBr and
BrꢀꢀꢀF halogen bindings within the crystal packing. The distance of BrꢀꢀꢀBr is 0.122 Å shorter
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
than the sum of van der Waals radius of two bromine atoms; the distance of BrꢀꢀꢀF is 0.118 Å
shorter than the sum of van der Waals radius of bromine and fluorine. The bond angle of Brꢀꢀꢀ
BrꢀꢀꢀF is 85.12°, indicating this is a TypeꢀII halogen bonding.18, 56, 61
In addition to the short contacts of BrꢀꢀꢀBr and BrꢀꢀꢀF halogen bindings55, 63ꢀ65, many short
contacts between carbons, and carbon to oxygen, showing relatively stronger π−π quadrupole
interactions between adjacent molecules compared to other weak intermolecular interactions
observed in the crystal structure. Further, PdꢀꢀꢀC short contacts are also observed, perhaps due to
Pdꢀꢀꢀπ interaction that is similar to the Pdꢀꢀꢀallylic interactions.53 The strong π−π quadrupole
interactions and Pdꢀꢀꢀπ interaction were further demonstrated by a crystal structure of a tꢀbutyl
substituent analog, compound 3 (Figure 3). Two bulky tꢀbutyl groups possess very large steric
hindrance that is against the two Pd complex cores packing together through π−π quadrupole
interactions and Pdꢀꢀꢀπ interaction. However, these intermolecular interactions are strong enough
to slightly bend the entire metal complex core to reach to an equilibrium between attractive π−π
quadrupole interactions and Pdꢀꢀꢀπ interactions as well as repulsive interactions caused by steric
hindrance of the tꢀbutyl groups. The molecular packing motif clearly shows the bulky tꢀbutyl
groups and perfluorobutyl groups are away from each other similar to solution phase separation
between flourocarbon and hydrocarbon solvents.66ꢀ68
ACS Paragon Plus Environment
14

Page 15 of 35
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2. Crystal packing of compound 2. Left, side view of a crystal packing column; right:
halogen bonding involving bromine and fluorine in compound 2. The short contact distances
and angles involving Br and F atoms are listed here, other short contact distances are given in the
supporting information.
Figure 3. Crystal packing of compound 3. Left: side view of a π−π stacked column shows
slightly bended coordination core. Right: top view of the same π−π stacked column shows
ACS Paragon Plus Environment
15

Crystal Growth & Design
Page 16 of 35
1
2
3
4
perfluorobutyl and tꢀbutyl groups avoid each other to minimize the steric hindrance to keep the
5
6
7
π−π stacked molecular packing motif.
8
9
The bent structure of the coordination core was further observed in −OMe substituted Pd
complex (compound 4) and the degree of structure bending was further amplified by this strong
electron donating substituent. Additionally, the electronꢀdonating −OMe group and electronꢀ
withdrawing –nꢀC4F9 group located at the opposite ends of the molecule, establishing a perfect
“PushꢀandꢀPull” electronic effect (or DꢀA effect) in compound 4. This effect creates a larger
uneven electron density distribution across the molecular surface, resulting in stronger
quadrupoleꢀquadrupole interaction between two adjacent molecules compared to similar
molecules without a strong PushꢀandꢀPull effect (i.e. compound 1). This interaction tends to pull
two adjacent molecules close to each other which results in a smaller interplanar distance. On
the other hand, the steric hindrance of a −OMe group resists two adjacent molecules getting
closer. It is apparent that the quadrupoleꢀquadrupole interaction is strong enough to overcome
the energy needed for bending the molecule and reaching the optimized position while only
slightly changing the interplanar distance, but maintained overall lamellar structure. The
significant bending in the same π stack results in the molecules pairing up to reach a more stable
structure. However, it is still a significant challenge to judge if the structure is indeed a
thermodynamically stable structure from the crystal engineering view point. High level quantum
mechanical energy calculation is needed to further explain this observation.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment
16

Page 17 of 35
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 4. Crystal packing of compound 4. Left: side view of a π−π stacked column shows
bended coordination core. Right: top view of the same π−π stacked column shows perfluorobutyl
and −OMe groups avoid each other to minimize the steric hindrance to keep the π−π stacked
molecular packing motif.
When we change the bipydrine ligand in compound 1 to phenanthroline ligand, the overall
molecular packing motif of a new compound 5 still maintains lamellar π−π stacked structure
without significant change though slight changes in antiparallel stacking is observed when
compared to compound 1 (see SI, Figure Sꢀ1). The interplanar distance for the structure of
compound 5 is 3.244 Å, slightly longer than that of compound 1.
One common observation for these five Pd complexes is that the interplanar distances are
smaller than, or at least comparable with, that of perfluoroalkylated aromatics with similar
molecular topology and size.23 The large steric hindrance caused by the tꢀbutyl groups or –OMe
groups does not significantly change the overall interplanar distances though bending of the
molecular core structures were observed. For all these perfluoroutylated Pd complexes, we
ACS Paragon Plus Environment
17

Crystal Growth & Design
Page 18 of 35
1
2
3
4
5
6
7
8
9
observed multiple short CꢀFꢀꢀꢀFꢀC contacts in the crystal structures which are similar to
previously reported perfluoalkylated aromatics.15, 23, 27 Though we did not observe direct PdꢀPd
short contact in these five complexes, we did observe the short contact between Pd and carbon
and/or oxygen in the complex core where the π orbitals are located. This observation is
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
consistent with recently reported metalꢀπ interactions.69, 70 This metalꢀπ interaction, perhaps,
plays an important role in bring the two squareꢀplanar metal complexes closer when compared to
its counterpart of the perfluoalkylated aromatics.
In a Pt(II) complex (compound 6) having same ligands compared to compound 1, we clearly
observed PtꢀꢀꢀPt short contact though the interplanar distance is slightly longer (3.220 Å for
compound 6 vs. 3.199 Å for compound 1) than that of compound 1, mainly caused by a larger
radius of platinum compared to that of palladium. The molecular packing motif of compound 6
is almost identical to compound 1 (Figure 5). The PtꢀꢀꢀPt short contact falls in a zigꢀzag mode
within a π−π stacked column as shown in Figure 5.
ACS Paragon Plus Environment
18

Page 19 of 35
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 5. Molecular packing and interplanar distances of compound 6. Left, side view of a π−π
stacked column; right, top view of the same column.
Solid state structures of chargeꢀneutral molecular materials are determined by the relative
strength of each different type of weak nonꢀcovalent intermolecular interactions involved. Any
disturbance of these weak nonꢀcovalent intermolecular interactions could potentially change the
solid state structure though molecular structure remains unchanged. We discussed earlier that
the anhydrous form of compound 1 forms perfect lamellar 1ꢀD column structure insulated by
perfluoroalkyl substituents. Viewing the crystal packing structure along the cꢀaxis, we observed
that each metal complex column core (cycled with semitransparent red ovals) is surrounded by
perfluorobutyl substituents (Figure 6). Due to potential electrical insulating properties of the
perfluoroalkyl groups and closely π−π stacked columns, we expect that this type of materials
could potentially be oneꢀdimensional semiconductor materials along cꢀaxis of the single crystal
though significant challenges on growing and handling large size fragile organic single crystal
remains.
ACS Paragon Plus Environment
19

Crystal Growth & Design
Page 20 of 35
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 6. Crystal packing of compound 1 view along cꢀaxis of 2x2x2 unit cells. Red ovals
highlight the column stacks in the crystal.
2.3 Physicochemistry properties characterization
The fundamental physiochemical properties of these Pd and Pt complexes were characterized
by cyclic voltammetry and UVꢀvisible absorption spectroscopy. All the compounds exhibit
reversible single electron transfer reduction and oxidation (Figure 7) in 1,2ꢀdifluorobenzene
(DFB) solution with 0.1 M TBAPF6 as supporting electrolyte on Pt working electrode. The first
oxidation for compounds 1ꢀ4 occurs at very similar potentials around 0.4 V with compound 2
slightly higher and compound 4 slightly lower due to the electronic effect of the substituents on
bipyridine ligand. The first oxidation potential of phenanthroline containing compound 5 is
almost identical to compound 1. The first reduction potentials of compounds 1ꢀ4 show strong
ACS Paragon Plus Environment
20

Page 21 of 35
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
dependence on the electronic effect of the substituents on bipyridine ligand where electron
withdrawing Br substituents shift its first reduction potential to the positive direction for 232 mV
compared to compound 1. In contrast, electron donating –OMe groups shift its first reduction
potential to the negative direction for 156 mV compared to compound 1. These observations on
redox potential shift upon substitution of bipyridine ligand suggest the first reduction of these
compounds occurs mainly on bipyridine ligands and the first oxidation occurs on
bisperfluorobutylated catechol ligand.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 7. Cyclic voltammogram of compounds 1−6 in 1,2ꢀdifluorobenzene (DFB) with 0.1 M
TBAPF6 as supporting electrolyte. Potential sweep rate 100 mV/s.
ACS Paragon Plus Environment
21

Crystal Growth & Design
Page 22 of 35
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 8. Solid state UVꢀvisible absorption spectra of compounds 1 through 6 (pure sample).
The absorption spectra of these compounds in the solid state were measured on a Carryꢀ5000
UVꢀvisibleꢀNearꢀIR spectrometer with the Praying Mantis™ Diffuse Reflection Accessory
between 200 nm to 800 nm (Figure 8). The compounds show a broad and featureless absorption
band at long wavelength. We calculated the optical bandgap according to the onsite bandgap
calculation procedure which is commonly accepted in the materials chemistry community.71ꢀ75
The value of the onsite optical bandgap is in line with the bandgap value estimated from solution
redox potential with compounds 3 and 6 slightly large difference between those two bandgap
values. The long wavelength absorption peaks of these compounds are likely caused by metal to
ligands charge transfer (MLCT).76, 77 However, pinpointing the exact transit of these absorption
peaks would require further TDꢀDFT calculation which gives the detailed contribution of transit
mode. Further investigation in OFET assembly and testing is underway; we hope that the idea
presented in this report will shed some light on engineering new organic semiconductor
materials.
ACS Paragon Plus Environment
22

Page 23 of 35
Crystal Growth & Design
1
2
3
4
5
6
Table 2. Measured interplanar distances, electrochemical properties, and optical bandgaps of
compounds 1 through 6.
7
8
9
red
ox
EC
opt
Cmpd Packing
mode
E1/2
/
E1/2
/
Egap
eV
/
Egap
λ
max/nm
/eVb
ε/(L molꢀ1
dπꢀπ/Å
V
V
/ eVd
2.150
1.954
2.048
cmꢀ1)c
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3.199
3.196
502/2.47
516/2.48
456/2.72
3.3x103
3.8x103
3.6x103
ꢀ1.693 0.455
ꢀ1.461 0.479
ꢀ1.813 0.422
2.148
1.940
2.235
1
2
3
π−π
π−π
π−π
3.319
(3.275)a
3.315
515/2.49
466/2.66
498/2.49
3.4x103
6.7x103
3.6x103
ꢀ1.849 0.381
ꢀ1.720 0.460
ꢀ1.667 0.547
2.230
2.180
2.214
2.302
2.169
1.972
4
5
6
π−π
π−π
π−π
(3.182)a
3.244
(3.214)a
3.220
a, shortest distance between Pd atom to the average plane of the adjacent molecule; b, solution
maximum absorption in nm and in eV units; c, molar absorption coefficiency of the maximum
absorption peak (long wavelength one) in solution; d, optical bandgap measured from the solid
state absorption spectra.
3. Conclusion
In summary, with six examples of Pd and Pt complexes containing bisperfluorobutylated
catechol ligand we demonstrate that four coordinating squareꢀplanar metal complexes with
perfluoroalklated ligand could form lamellar π−π stacked structures similar to what we observed
in perfluoroalkylated aromatic compounds. Compared to those previously reported
perfluoroalkylated aromatic compounds, our current results further support that molecular
topology and relative strength of the weak nonꢀcovalent intermolecular interactions are key to
the solid state structures in chargeꢀneutral molecular materials. The crystal structures together
with the electrochemical and optical results show that we can tune the electronic properties of the
ACS Paragon Plus Environment
23

Crystal Growth & Design
Page 24 of 35
1
2
3
4
5
6
7
8
9
materials through modification of substituents on the ligands without worry about the disruption
of overall lamellar π−π stacked packing motif in squareꢀplanar transition metal complexes.
ASSOCIATED CONTENT
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Supporting Information. Detailed experimental procedures, NMR and mass spectra, additional
structure information, cif and checkcif files, additional references. This material is available free
of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Haoran.Sun@usd.edu
Author Contributions
All authors have given approval to the final version of the manuscript.
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
Authors are thankful for the financial support from the NSF (CAREER program: CHE1355677).
Authors also acknowledge NSFꢀEPSCoR (EPSꢀ0554609) for the purchase of a Bruker SMART
APEX II CCD diffractometer and NSFꢀMRI grant (CHEꢀ1229035) for the purchase of a Bruker
400 MHz NMR spectrometer. Authors thank Prof. Andrew Sykes for helpful discussion on Pt
interactions and help in assisting in resolving disordered structure in compound 4.
ACS Paragon Plus Environment
24

Page 25 of 35
Crystal Growth & Design
1
2
3
4
REFERENCES
5
6
7
8
9
(1) Buehler, M. J. Materials by desingꢀa perspective from atoms to structures. MRS Bull.
2013, 38, 169ꢀ176.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(2) Pigge, F. C. Losing control? "Design" of crystalline organic and metalꢀorganic networks
using conformationally flexible building blocks. CrystEngComm 2011, 13, 1733ꢀ1748.
(3) Stupp, S. I.; Palmer, L. C. Supramolecular Chemistry and SelfꢀAssembly in Organic
Materials Design. Chem. Mater. 2014, 26, 507ꢀ518.
(4) Zhou, H.ꢀC.; Long, J. R.; Yaghi, O. M. Introduction to MetalꢀOrganic Frameworks.
Chem. Rev. 2012, 112, 673ꢀ674.
(5) Ding, S.ꢀY.; Wang, W. Covalent organic frameworks (COFs). From design to
applications. Chem. Soc. Rev. 2013, 42, 548ꢀ568.
(6) Xu, H.; Chen, R.; Sun, Q.; Lai, W.; Su, Q.; Huang, W.; Liu, X. Recent progress in metalꢀ
organic complexes for optoelectronic applications. Chem. Soc. Rev. 2014, 43, 3259ꢀ3302.
(7) O'Keeffe, M.; Yaghi, O. M. Deconstructing the Crystal Structures of MetalꢀOrganic
Frameworks and Related Materials into Their Underlying Nets. Chem. Rev. 2012, 112, 675ꢀ702.
(8) Desiraju, G. R. Designer crystals: intermolecular interactions, network structures and
supramolecular synthons. Chem. Commun. 1997, 1475ꢀ1482.
(9) Rowsell, J. L. C.; Yaghi, O. M. Metalꢀorganic frameworks: a new class of porous
materials. Microporous Mesoporous Mater. 2004, 73, 3ꢀ14.
ACS Paragon Plus Environment
25

Crystal Growth & Design
Page 26 of 35
1
2
3
4
(10) Dunitz, J. D.; Gavezzotti, A. How molecules stick together in organic crystals: weak
5
6
intermolecular interactions. Chem. Soc. Rev. 2009, 38, 2622ꢀ2633.
7
8
9
(11) Claessens, C. G.; Stoddart, J. F. πꢀπ Interactions in selfꢀassembly. J. Phys. Org. Chem.
1997, 10, 254ꢀ272.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(12) Barbour, L. J.; Atwood, J. L. Nonꢀcovalent interactions exert extraordinary influence
over conformation and properties of a wellꢀknown supramolecular building block. Chem.
Commun. 2001, 2020ꢀ2021.
(13) Desiraju, G. R. Reflections on the hydrogen bond in crystal engineering. Cryst. Growth
Des. 2011, 11, 896ꢀ898.
(14) MacGillivray, L. R. Organic Synthesis in the Solid State via HydrogenꢀBondꢀDriven
SelfꢀAssembly. J. Org. Chem. 2008, 73, 3311ꢀ3317.
(15) Sun, H.; Tottempudi, U. K.; Mottishaw, J. D.; Basa, P. N.; Putta, A.; Sykes, A. G.
Strengthening πꢀπ Interactions While Suppressing Csp2ꢀH···π (TꢀShaped) Interactions via
Perfluoroalkylation: A Crystallographic and Computational Study That Supports the Beneficial
Formation of 1ꢀD πꢀπ Stacked Aromatic Materials. Cryst. Growth Des. 2012, 12, 5655ꢀ5662.
(16) Aakeroy, C. B.; Champness, N. R.; Janiak, C. Recent advances in crystal engineering.
CrystEngComm 2010, 12, 22ꢀ43.
(17) Metrangolo, P.; Neukirch, H.; Pilati, T.; Resnati, G. Halogen Bonding Based Recognition
Processes: A World Parallel to Hydrogen Bonding. Acc. Chem. Res. 2005, 38, 386ꢀ395.
(18) Metrangolo, P.; Resnati, G.; Pilati, T.; Biella, S. Halogen bonding in crystal engineering.
Struct. Bonding 2008, 126, 105ꢀ136.
ACS Paragon Plus Environment
26

Page 27 of 35
Crystal Growth & Design
1
2
3
4
(19) Sinnwell, M. A.; Baltrusaitis, J.; MacGillivray, L. R. Combination of Argentophilic and
5
6
PerfluorophenylꢀPerfluorophenyl Interactions Supports
a
HeadꢀtoꢀHead [2
+
2]
7
8
9
Photodimerization in the Solid State. Cryst. Growth Des. 2015, 15, 538ꢀ541.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(20) Stojakovic, J.; Whitis Avery, M.; Macgillivray Leonard, R. Discrete Doubleꢀtoꢀ
Quadruple Aromatic Stacks: Stepwise Integration of FaceꢀtoꢀFace Geometries in Cocrystals
Based on Indolocarbazole. Angew. Chem. Int. Ed. 2013, 52, 12127ꢀ12130.
(21) Sokolov, A. N.; Friscic, T.; MacGillivray, L. R. Enforced FaceꢀtoꢀFace Stacking of
Organic Semiconductor Building Blocks within HydrogenꢀBonded Molecular Cocrystals. J. Am.
Chem. Soc. 2006, 128, 2806ꢀ2807.
(22) Mukherjee, A.; Tothadi, S.; Desiraju, G. R. Halogen Bonds in Crystal Engineering: Like
Hydrogen Bonds yet Different. Acc. Chem. Res. 2014, 47, 2514ꢀ2524.
(23) Putta, A.; Mottishaw, J. D.; Wang, Z.; Sun, H. Rational Design of Lamellar πꢀπ Stacked
Organic Crystalline Materials with Short Interplanar Distance. Cryst. Growth Des. 2014, 14,
350ꢀ356.
(24) Mottishaw, J. D.; Sun, H. Effects of Aromatic Trifluoromethylation, Fluorination, and
Methylation on Intermolecular πꢀπ Interactions. J. Phys. Chem. A 2013, 117, 7970ꢀ7979.
(25) Sun, H.; Putta, A.; Kloster, J. P.; Tottempudi, U. K. Unexpected photostability
improvement of aromatics in polyfluorinated solvents. Chem. Commun. 2012, 48, 12085ꢀ12087.
(26) Sun, H.; Putta, A.; Billion, M. Arene Trifluoromethylation: An Effective Strategy to
Obtain AirꢀStable nꢀType Organic Semiconductors with Tunable Optoelectronic and Electron
Transfer Properties. J. Phys. Chem. A 2012, 116, 8015ꢀ8022.
ACS Paragon Plus Environment
27

Crystal Growth & Design
Page 28 of 35
1
2
3
4
5
6
7
8
9
(27) BaniKhaled, M. O.; Mottishaw, J. D.; Sun, H. Steering Power of Perfluoroalkyl
Substituents in Crystal Engineering: Tuning the πꢀπ Distance While Maintaining the Lamellar
Packing Motif for Aromatics with Various Sizes of πꢀConjugation. Cryst. Growth Des. 2015, 15,
2235ꢀ2242.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(28) Pavan, M. S.; Durga Prasad, K.; Guru Row, T. N. Halogen bonding in fluorine:
experimental charge density study on intermolecular F···F and F···S donorꢀacceptor contacts.
Chem. Commun. 2013, 49, 7558ꢀ7560.
(29) Osuna, R. M.; Hernandez, V.; Navarrete, J. T. L.; D'Oria, E.; Novoa, J. J. Theoretical
evaluation of the nature and strength of the F···F intermolecular interactions present in
fluorinated hydrocarbons. Theor. Chem. Acc. 2011, 128, 541ꢀ553.
(30) Baker, R. J.; Colavita, P. E.; Murphy, D. M.; Platts, J. A.; Wallis, J. D. FluorineꢀFluorine
Interactions in the Solid State: An Experimental and Theoretical Study. J. Phys. Chem. A 2012,
116, 1435ꢀ1444.
(31) Wang, C.; Dong, H.; Hu, W.; Liu, Y.; Zhu, D. Semiconducting πꢀConjugated Systems in
FieldꢀEffect Transistors: A Material Odyssey of Organic Electronics. Chem. Rev. 2012, 112,
2208ꢀ2267.
(32) Mei, J.; Diao, Y.; Appleton, A. L.; Fang, L.; Bao, Z. Integrated Materials Design of
Organic Semiconductors for FieldꢀEffect Transistors. J. Am. Chem. Soc. 2013, 135, 6724ꢀ6746.
(33) Shirota, Y.; Kageyama, H. Charge Carrier Transporting Molecular Materials and Their
Applications in Devices. Chem. Rev. 2007, 107, 953ꢀ1010.
ACS Paragon Plus Environment
28

Page 29 of 35
Crystal Growth & Design
1
2
3
4
(34) Sergeyev, S.; Pisula, W.; Geerts, Y. H. Discotic liquid crystals: a new generation of
5
6
organic semiconductors. Chem. Soc. Rev. 2007, 36, 1902ꢀ1929.
7
8
9
(35) Facchetti, A. Semiconductors for organic transistors. Mater. Today 2007, 10, 28ꢀ37.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(36) Diao, Y.; Lenn, K. M.; Lee, W.ꢀY.; BloodꢀForsythe, M. A.; Xu, J.; Mao, Y.; Kim, Y.;
Reinspach, J. A.; Park, S.; AspuruꢀGuzik, A.; Xue, G.; Clancy, P.; Bao, Z.; Mannsfeld, S. C. B.
Understanding Polymorphism in Organic Semiconductor Thin Films through Nanoconfinement.
J. Am. Chem. Soc. 2014, 136, 17046ꢀ17057.
(37) Tang, M. L.; Okamoto, T.; Bao, Z. HighꢀPerformance Organic Semiconductors:
Asymmetric Linear Acenes Containing Sulphur. J. Am. Chem. Soc. 2006, 128, 16002ꢀ16003.
(38) Noro, S.ꢀi.; Chang, H.ꢀC.; Takenobu, T.; Murayama, Y.; Kanbara, T.; Aoyama, T.; Sassa,
T.; Wada, T.; Tanaka, D.; Kitagawa, S.; Iwasa, Y.; Akutagawa, T.; Nakamura, T. MetalꢀOrganic
ThinꢀFilm Transistor (MOTFT) Based on a Bis(oꢀdiiminobenzosemiquinonate) Nickel(II)
Complex. J. Am. Chem. Soc. 2005, 127, 10012ꢀ10013.
(39) Hettiarachchi, C. V.; RawashdehꢀOmary, M. A.; Korir, D.; Kohistani, J.; Yousufuddin,
M.; Dias, H. V. R. Trinuclear Copper(I) and Silver(I) Adducts of 4ꢀChloroꢀ3,5ꢀ
bis(trifluoromethyl)pyrazolate and 4ꢀBromoꢀ3,5ꢀbis(trifluoromethyl)pyrazolate. Inorg. Chem.
2013, 52, 13576ꢀ13583.
(40) Omary, M. A.; Elbjeirami, O.; Gamage, C. S. P.; Sherman, K. M.; Dias, H. V. R.
Sensitization of Naphthalene Monomer Phosphorescence in a Sandwich Adduct with an
ElectronꢀPoor Trinuclear Silver(I) Pyrazolate Complex. Inorg. Chem. 2009, 48, 1784ꢀ1786.
ACS Paragon Plus Environment
29