Chemistry Reference
In-Depth Information
4 Indeno[2,1-
a
]fluorenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
4.1 Indeno[2,1-
a
]fluorene-11,12-diones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
4.2 Fully-Conjugated Indeno[2,1-
a
]fluorenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
5 Indeno[2,1-
b
]fluorenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
5.1 Indeno[2,1-
b
]fluorene-10,12-diones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
5.2 Fully-Conjugated Indeno[2,1-
b
]fluorenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
5.3 Other Indeno[2,1-
b
]fluorenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
6 Indeno[2,1-
c
]fluorenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
6.1 Indeno[2,1-
c
]fluorene-5,8-diones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
6.2 Fully-Conjugated Indeno[2,1-
c
]fluorenes . . . ......................................... 191
6.3 Other Indeno[2,1-
c
]fluorenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7 Conclusions .................................................................................. 192
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
1
Introduction
1.1 Background
Polycyclic aromatic hydrocarbons (PAHs), and polyarenes (PAs) in general, have
been the subject of great interest for over 150 years, and constitute a significant
cornerstone of the advancement of organic chemistry in the nineteenth and twenti-
eth centuries [
1
,
2
]. Initially discovered in the resins of fossil fuels, PAHs have been
observed in a myriad of environments that range from natural mineral deposits to
meteor rocks [
3
]. Isolation of PAH-rich tars and ashes has contributed not only to
modern purification and separation techniques commonly used today, but has also
brought forth fundamental concepts such as aromaticity, a topic that remains a
neverending source of discussion in the literature. Furthermore, efforts to elucidate
the reactivity of PAHs and PAs have resulted in the discovery of many novel
reaction mechanisms and catalytic pathways that represent
the foundation of
modern physical organic chemistry.
In the last quarter century, PAH and PA research has made a remarkable return
to the literature spotlight as compound accessibility and characterization has been
made easier with the advent of modern synthetic methods and instrumentation,
respectively [
4
-
6
]. One motivation for this resurgence lies with the unique
optoelectronic properties that PAHs and PAs possess due to their inherently high
levels of
-conjugation and delocalization. These attributes make PAHs and PAs
useful for a variety of materials applications such as organic light-emitting diodes
(OLEDs), field-effect transistors (OFETs), and photovoltaics (OPVs) [
7
,
8
]. Such
impetus has led to the development and expansion of various PAH classes, such as
higher order acenes [
9
,
10
] and condensed polycyclic aromatics [
11
-
13
]. Nontradi-
tional structures that incorporate five-membered cyclopentyl rings (CP-PAHs) such
as fullerenes [
14
] and buckybowls [
15
] have undergone rapid growth as well.
This review focuses on the pentacyclic indenofluorenes (IFs), another
reemerging class of CP-PAHs, where the B and D rings are each a five-membered
ring. First synthesized in the late nineteenth century by Gabriel [
16
], IF derivatives
p
