Expanded porphyrin-like structures based on twinned triphenylenes

Article abstract of DOI:10.1021/jo401551c

Triphenylene twins are intriguing structures, and those bridged through their 3,6-positions by dipyrromethene units give a new class of macrocycles that can be viewed as rigid, expanded porphyrin derivatives in which coplanarity is enforced in a formally antiaromatic π system. Somewhat surprisingly, however, macrocyclization leads to significant overall stabilization of the dipyrromethene chromophores.

Full text of DOI:10.1021/jo401551c

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Subscriber access provided by Queen's University Library
Note
Expanded porphyrin-like structures based on twinned triphenylenes
Hemant Gopee, Xiangfei Kong, Zhiqun He, Isabelle Chambrier, David L.
Hughes, Graham J. Tizzard, Simon J. Coles, and Andrew N. Cammidge
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo401551c • Publication Date (Web): 29 Aug 2013
Downloaded from http://pubs.acs.org on September 3, 2013
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.
The Journal of Organic Chemistry 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.

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Page 1 of 21
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Expanded porphyrinꢀlike structures based on twinned
triphenylenes
10
11
12
13
14
15
16
17
18
19
20
21
Hemant Gopee,† Xiangfei Kong,†,§ Zhiqun He,§ Isabelle Chambrier,† David L. Hughes,† Graham J.
Tizzard,¶ Simon J. Coles¶ and Andrew N. Cammidge*,†
†School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK. § Key Laboratory of
Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology,
Beijing Jiaotong University, Beijing 100044, PR China. ¶ UK National Crystallography Service, School
of Chemistry, University of Southampton SO17 1BJ, UK.
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
a.cammidge@uea.ac.uk
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required
according to the journal that you are submitting your paper to)
Abstract
Triphenylene twins are intriguing structures and those bridged through their 3,6ꢀpositions by
dipyrromethene units give a new class of macrocycle that can be viewed as rigid, expanded porphyrin
derivatives in which coꢀplanarity is enforced in a formally antiaromatic πꢀsystem. Somewhat
surprisingly however, macrocyclization leads to significant overall stabilization of the dipyrromethene
chromophores.
1
ACS Paragon Plus Environment

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
The Journal of Organic Chemistry
Page 2 of 21
Macrocyclic, aromatic chromophores are extremely important chemical entities, exemplified by
porphyrin and phthalocyanine.1 The former are widespread in Nature and their function has inspired
imaginative purposeꢀdesigned analogues. Their function and applications are too numerous and diverse
to list, spanning the full scientific spectrum from biochemistry through to electronic engineering, with
corresponding applications from medicine through to ubiquitous consumer devices.1 Synthetic
breakthroughs have advanced the scope of materials available, and an area of particular recent interest
has been the investigation of coreꢀmodified structures to enhance and expand materials properties.
Structures include expanded and contracted systems, confused and mixedꢀheteroatom systems, and
hybrid structures.2ꢀ8 The chemistry of expanded porphyrins in particular has received accelerated
attention and progressed rapidly over recent years.9 Advances include substantial synthetic effort and
investigation of “higher” porphyrinoids, most extensively the hexaphrins (2) but including octaphrins
and others.10 Separately more complex and diverse expanded structures likened to porphyrins have been
successfully targeted9 and representative extreme structures include expanded system 311 and rosarin
derivative 4 (Figure 1).12
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
N
NH
N
N
NH
N
N
HN
HN
N
N
1
H
2
N
N
C6F5
C6F5
N
N
H
S
N
NH
N
EtO2C
HN
N
3
5
C6F5
4
Figure 1. Parent structure of porphyrin 1 and triphenylene 5, plus examples of more exotic
porphyrinoids 2-4.
Triphenylenes are an important class of discotic benzenoid aromatic compounds. They are the most
widely studied discotic liquid crystals.13 Synthetic advances have similarly allowed access to diverse
2
ACS Paragon Plus Environment

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Page 3 of 21
The Journal of Organic Chemistry
symmetrical and unsymmetrically substituted derivatives so that their properties, such as factors
1
2
3
4
5
6
7
8
9
controlling liquid crystal behavior, and applications could be interrogated.14 In the field of discotic
liquid crystals, the majority of mesophases are columnar in structure. Most recently we have applied our
synthetic refinements to open the way to twinned macrocyclic structures linked through the triphenylene
3,6ꢀpositions. Using this approach strained and formally antiaromatic systems can be produced – the
links through triphenylene 3,6ꢀsites allows completion of conjugation pathways like in simple 1,2ꢀ
disubstituted benzenes. However, the links are separated in space preventing destructive pericyclic
processes. The twinning geometry, if carefully designed, leads to a void region in the centre of the
molecule, such as in twins 6 and 7 (Figure 2). Columnar organization would lead to a void region
through the columnꢀcentre and columnar mesophase formation is therefore suppressed. Selfꢀorganisation
into the rare discotic nematic mesophase is then observed.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
Figure 2. Rigid, nematic twins and the target twinned triphenylenes that have an expanded porphyrinꢀ
like core.
The structural motif therefore appears both useful and versatile, and we recognized that interesting
molecular variants could be envisaged through more imaginative choice of linking units. Core structures
represented by macrocycle 8 (Figure 2) were conceived; they can be considered direct but distant
relatives of porphyrins and are therefore expected to mimic their cousins in some important respects.
3
ACS Paragon Plus Environment