Deciphering the potentiometric properties of (porphinato)zinc(ii)-derived supramolecular polymers and related superstructures

Article abstract of DOI:10.1039/c8tc02979b

Because modulating the structure-function relationships of π-conjugated superstructures opens fresh opportunities to tune the electronic structures of semiconducting materials, self-assembled architectures have emerged as pivotal candidates to engineer optoelectronic devices. While the photophysical and electrical properties of 1-dimensional supramolecular polymers have been extensively explored, establishing their fundamental potentiometric properties using reliable electrochemical measurements has been less scrutinized and would benefit the engineering of semiconducting materials. In this regard, elucidating the energy level of valence and conduction bands that delineate the electronic structure of self-assemblies is critical to unveiling the parameters that regulate their structure-function properties. In the present contribution, design principles to engineer 2-dimensional nanosheets, nanowires, fibers and amorphous solids from (porphinato)zinc(ii) (PZn) building blocks have been elucidated by modifying the structural properties of the side chains that flank PZn-based cores. As these self-assemblies feature identical redox-active building blocks but evidence different solid-state morphologies, the elucidation of their potentiometric properties reveals important structural parameters that regulate the potentials at which holes and electrons are injected into the valence and conduction bands of these hierarchical materials. While self-assembly conformations modestly impact valence band energies, superstructures built from H-type aggregates feature a conduction band energy stabilized by more than 350 meV with respect to those constructed from J-type aggregates.

Full text of DOI:10.1039/c8tc02979b

Journal of
Materials Chemistry C
View Article Online
View Journal
PAPER
Deciphering the potentiometric properties of
(porphinato)zinc(II)-derived supramolecular
Cite this:DOI: 10.1039/c8tc02979b
polymers and related superstructures†‡
Chuan Liu,
Kaixuan Liu, Jared Klutke, Adam Ashcraft, Samantha Steefel and
Jean-Hubert Olivier
*
Because modulating the structure–function relationships of p-conjugated superstructures opens fresh
opportunities to tune the electronic structures of semiconducting materials, self-assembled architectures
have emerged as pivotal candidates to engineer optoelectronic devices. While the photophysical and
electrical properties of 1-dimensional supramolecular polymers have been extensively explored,
establishing their fundamental potentiometric properties using reliable electrochemical measurements
has been less scrutinized and would benefit the engineering of semiconducting materials. In this regard,
elucidating the energy level of valence and conduction bands that delineate the electronic structure of
self-assemblies is critical to unveiling the parameters that regulate their structure–function properties. In
the present contribution, design principles to engineer 2-dimensional nanosheets, nanowires, fibers and
amorphous solids from (porphinato)zinc(II) (PZn) building blocks have been elucidated by modifying the
structural properties of the side chains that flank PZn-based cores. As these self-assemblies feature
identical redox-active building blocks but evidence different solid-state morphologies, the elucidation of
their potentiometric properties reveals important structural parameters that regulate the potentials at
which holes and electrons are injected into the valence and conduction bands of these hierarchical
materials. While self-assembly conformations modestly impact valence band energies, superstructures
built from H-type aggregates feature a conduction band energy stabilized by more than 350 meV with
respect to those constructed from J-type aggregates.
Received 17th June 2018,
Accepted 6th August 2018
DOI: 10.1039/c8tc02979b
rsc.li/materials-c
states.23 In this regard, benchmark theoretical studies have
unambiguously demonstrated the cardinal role played by super-
Introduction
Controlling the aggregation of p-conjugated building blocks to structure conformation in delineating their electronic properties
construct well-defined nano-to-mesoscale semiconductors fuels whereas minor modification of repeating unit registry can drastically
interest in applications such as light energy transduction,1–7 impact the electronic coupling between building blocks.24–27
charge transport,8–12 and spintronics.13–16 For example, pro-
Advances in supramolecular chemistry have unraveled important
gramming the assembly of 1-dimensional (1D) superstructures design principles that have led to the creation of hierarchical
at the molecular level has provided new platforms with which materials equipped with appealing structure–function properties
to not only deepen the understanding of light–matter inter- relevant to energy capture, conversion, and storage.28 The
action but also to manipulate the flow of excitons and charge elucidation of the mechanisms that govern formation of 1D
carriers.17–22 The emergence of electronic properties evidenced and 2-dimensional (2D) supramolecular polymers (SPs) has
in organic superstructures that feature stacks of redox-active provided fresh opportunities to modulate the electronic properties
p-conjugated units traces its genesis from the interaction of of these materials.29–33 For example, pioneering works have
frontier molecular orbitals of each building block that ultimately demonstrated the selective assembly of (porphinato)zinc(II)
enforces the formation of new energy levels and spectroscopic and perylene diimide building blocks into H-aggregates and
J-aggregates by manipulating the pathway complexity that
regulates the formations of these supramolecular polymers.34–44
In addition, investigation of the excited state of 1D supra-
Department of Chemistry, University of Miami, Cox Science Building,
1301 Memorial Drive, Coral Gables, 33146, USA. E-mail: jh.olivier@miami.edu
† This paper is dedicated to Margot. Welcome to the world little girl.
molecular polymers using pump–probe time-resolved spectroscopy
‡ Electronic supplementary information (ESI) available: Synthesis, characteriza-
in the nanosecond and femtosecond time domains has unveiled
tion and aggregation mechanisms of redox-active building blocks. AFM, absorp-
tion spectra, NMR, IR, MS, and cyclic voltammetry. See DOI: 10.1039/c8tc02979b exciton delocalization length and charge carrier generation.45–48
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C

View Article Online
Paper
Journal of Materials Chemistry C
Undeniably, developing strategies to fine tune the optical properties
of p-conjugated aggregates is critical for the engineering of
electro-optical devices.
While the photophysical and electrical properties of 1D
supramolecular polymers have been vastly investigated, elucidation
of their potentiometric properties using reliable electrochemical
measurement methods and internal references has attracted less
attention. It is important to note that exciton dissociation and
free-charge carrier recombination are processes that regulate the
performance of optoelectronic devices and they are intimately
related to the valence and conduction band energies of semi-
conducting materials.18,49 In this regard, it is critical to develop a
fundamental understanding of the potentiometric properties that
characterize supramolecular polymers to illuminate the structural
parameters that regulate the energies of valence and conduction
bands for this class of self-assembled semiconductors. Electro-
chemical techniques have been well-exploited to reliably deter-
mine the redox potentials of covalent semiconducting polymers
and, most recently, semiconducting carbon nanotubes.50,51 In the
present contribution, we elucidate the potentiometric properties
of semiconducting superstructures using cyclic voltammetry
experiments. By exploring the electronic structure of hierarchical
materials built from (porphinato)zinc(II) cores, we demonstrate
that conformation of organic self-assemblies significantly modulates
the valence and conduction band energies.
Scheme 1 Molecular structures of the (porphinato)zinc(II) building blocks
exploited to construct hierarchical self-assemblies. Detailed synthesis
protocols can be found in the ESI.‡ Please note that racemic functional
groups have been utilized to synthesize PZn-OAlk-based building blocks.
stabilization of the conduction band energy is evidenced for
1D nanowires when compared to fiber-like compositions and
suggests that parameters such as the screening effect must be
considered when probing the conduction and valence band
energies of semiconducting self-assemblies.
Results and discussion
Self-assembly mechanisms of PZn-OAlk-PBA, PZn-OAlk-BA,
Because of their unique optical and electronic properties,52–57 and PZn-OTEG-PBA building blocks have been elucidated by
porphyrin-based chromophores have been extensively studied in temperature-dependent aggregation experiments chronicled in
solution and in the solid state, and they have been successfully Fig. 1. For all experiments, porphyrin solutions were heated
exploited as light-harvesting and charge transport media in a at the indicated temperature to ensure that building blocks
plethora of electro-optical devices.58,59 The elucidation of para- are fully individualized. Ground state electronic absorption
meters that govern formations of some supramolecular polymers spectrum recorded for PZn-OAlk-PBA at 100 1C in 9% DMF in
built from porphyrin-based units as unique building blocks has toluene features a sharp B-band at 453 nm and Q-band absorption
only recently been reported;34–38 it is worth noting that only centered at 664 nm (e = 20 000 Mꢀ1 cmꢀ1; f = 0.100) that are
a handful of studies have investigated the structure–function spectral attributes of individualized (porphinato)zinc(II) chromo-
properties of porphyrin-derived supramolecular polymers. To phores. The descent to 0 1C is accompanied by: (1) decrease of the
gain a deeper understanding of the electronic properties of B-band oscillator strength ( f1001C = 0.638 - f01C = 0.167), (2) the
porphyrin-derived SPs, the three building blocks PZn-OAlk-PBA, concomitant rise of novel absorptive features centered at 430 and
PZn-OAlk-BA and PZn-OTEG-PBA presented in Scheme 1 have 409 nm, (3) a 371 cmꢀ1 hypsochromic shift of the Q-band
been engineered and their self-assembly mechanisms were transition. Taken together, these emergent spectral signatures
elucidated using temperature-dependent aggregation study. Side suggest the formation of H-type aggregate upon cooling. To
chains that flank each (porphinato)zinc(II) unit feature amide elucidate the assembly mechanism that governs the aggregation
functional groups well-recognized to engender the formation of of PZn-OAlk-PBA building blocks, the degree of aggregation (a) as a
non-covalent interactions by means of hydrogen bonding.60 In function of temperature was calculated following eqn S1 (ESI‡) and
addition, to further explore the self-assembly energy landscape, is presented as inset in Fig. 1a. The observed sigmoidal shape is
modification of the porphyrin cores by introducing 3,5-bis(tri- characteristic of an isodesmic supramolecular polymerization
ethyleneglycoxy)phenyl substituents at the 10,20-positions equips mechanism. Fitting the data using the model developed by van der
the PZn-OTEG building block with amphiphilic character. Exploiting Schoot61 (see ESI‡) provides an elongation chain constant of 3.5 ꢁ
atomic force microscopy, we demonstrate that the morphology of 105 molꢀ1, and a change of enthalpy DHe = ꢀ80.71 kJ molꢀ1 that
superstructures built from drop-casted solution can be regulated as a accompanied the supramolecular polymerization process.
function of precursor properties. While supramolecular polymers
The self-assembly mechanism of PZn-OAlk-BA building
formed by temperature-induced self-assembly show 1D fiber-like blocks recorded in toluene (c = 6.5 ꢁ 10ꢀ6 M) contrasts that
materials and 2D nanosheets, elementary 1D nanowires can elucidated for PZn-OAlk-PBA and underscores the cardinal role
self-construct in the solid state by drop-casting solubilized played by the structural side chains that flank the redox active
building blocks. Redox potential measurements performed on sub-units. The ground state electronic absorption spectrum
these hierarchical materials have unveiled important structure– recorded at 110 1C features spectral signatures characteristic
function properties. For identical redox active cores, a drastic of individualized PZn-OAlk-BA building blocks: (1) intense
J. Mater. Chem. C
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Journal of Materials Chemistry C
Paper
features centered at 417, 434, and 517 nm in addition to a
411 cmꢀ1 bathochromic shift of the Q-band transition. These
spectral signatures indicate the formation of J-type aggregate. A
close examination of the curve that relates degree of aggregation
(a) as a function of temperature reveals a non-sigmoidal shape
characterized by an abrupt increase of aggregation below a specific
temperature. These aggregative properties are reminiscent of a
nucleation–elongation mechanism that regulates the formation of
supramolecular PZn-OAlk-BA polymers. It is worth noting that the
average length of the stack hNi Te at the critical elongation
temperature Te = 102 1C corresponds to a dimer intermediate
that evolves toward a supramolecular polymer built from 150
repeating units at 0 1C (see ESI‡ for detailed explanation).
The elongation process is associated with a change of enthalpy
DHe = ꢀ55.1 kJ molꢀ1
.
When compared to PZn-OAlk-PBA, the amphiphilic char-
acter conferred by the four pendant triethylene glycol side
chains featured on the PZn-OTEG-PBA building block impacts
the aggregation mechanism that regulates formation of supra-
molecular PZn-OTEG-PBA polymer. While at 110 1C, PZn-OTEG-
PBA units exist as individualized building blocks as evidenced
by the absorption spectrum recorded in toluene (c = 4.7 ꢁ
10ꢀ6 M) and presented in Fig. 1c, excursion to room temperature
favours the formation of H-type aggregate confirmed by the
hypsochromic shift of the Q-band from 642 nm to 636 nm in
addition to the formation of novel absorptive features on the blue
edge of the B-band at 419 nm (e = 20 650 Mꢀ1 cmꢀ1; f = 0.175) and
431 nm (e = 29 200 Mꢀ1 cmꢀ1; f = 0.157). Despite the fact that the
shape of the curve displaying the degree of aggregation as a
function of temperature (inset, Fig. 1c) suggests a nucleation–
elongation mechanism, fitting the data using the conventional
cooperative model has revealed unsuccessful. Surprisingly, while
the elongation regime can be successfully treated exploiting the
well-accepted van der Shoot model,61 the nucleation process
differs to some extent from the conventional uphill cooperative
model. The linear increase of degree of aggregation as a function
of temperature may suggest a nucleation step that processes
through a downhill mechanism model.62
To further investigate the role played by porphyrin-derived
precursors in regulating final superstructure conformations, AFM
was utilized to scrutinize the solid-state morphologies of drop-
casted porphyrin solutions. Fig. 2 and 3 are representative AFM
images that chronicle the structural properties of drop-casted
PZn-OAlk-PBA, PZn-OAlk-BA and PZn-OTEG-PBA porphyrin pre-
cursors. Please note that the following discussion compares
morphologies of solid-state materials constructed by exploiting
individualized PZn unit and supramolecular PZn polymer as primary
building blocks. Unambiguously demonstrated by ground-state
electronic absorption spectroscopy, PZn-OAlk-PBA building blocks
Fig. 1 Ground-state electronic absorption spectra that chronicle the
aggregation of PZn-derived building blocks as a function of temperature.
(a) PZn-OAlk-PBA building blocks in 9% DMF in toluene solution, c = 5.7 ꢁ
10ꢀ5 M, optical path length = 2 mm; (b) PZn-OAlk-BA building blocks in
toluene solution, c = 6.5 ꢁ 10ꢀ6 M, optical path length = 10 mm; (c) PZn-
OTEG-PBA building blocks in toluene solution, c = 4.7 ꢁ 10ꢀ6 M, optical path
length = 10 mm. For all measurements, a cooling rate of 1 K minꢀ1 was utilized.
Insets in all the panels correspond to the degree of aggregation (a) as a
function of temperature calculated from the attenuation of the extinction
coefficient at 453 nm (green circles); the orange lines represent the resulting
fits using the temperature-dependent isodesmic (a) and cooperative model
(b and c).
porphyrin-derived B-band absorption centered at 453 nm and in DMF solution remain individualized at room temperature
associated with an oscillator strength of 0.830, and (2) a (see Fig. S1, ESI‡) while temperature treatment of a 9% DMF in
dominant porphyrin-derived Q-band absorption centered at toluene solution enables formation of supramolecular polymer
651 nm (e = 27 300 Mꢀ1 cmꢀ1; f = 0.0917). Drastic perturbations compositions. These conformational discrepancies elucidated
of these spectral attributes can be diagnosed upon cooling to in solution transpire as well in the solid state as underscored
0 1C: (1) decrease of the B-band oscillator strength ( f1001C
=
when comparing Fig. 2a and b. When deposited from a DMF
0.830 - f01C = 0.515), and (2) the apparition of new absorptive solution, PZn-OAlk-PBA building blocks interact along a 1D axis
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C

View Article Online
Paper
Journal of Materials Chemistry C
Fig. 2 Topographic intermittent contact mode AFM acquired and associated height profiles recorded for drop-casted: (a) [PZn-OAlk-PBA]Agg
aggregates that originate from individualized PZn-derived building blocks in DMF solution; (b) [PZn-OAlk-PBA]Fib fibers constructed from parent
PZn-derived supramolecular polymer in 9% DMF in toluene solution; (c) [PZn-OAlk-BA]NW nanowires built from individualized PZn-derived building
blocks in DMF solution; (d) [PZn-OAlk-BA]NS nanosheets engineered from parent PZn-derived supramolecular polymer in toluene. For each panel, the
height profile corresponds to the associated numbers on the AFM images.
parallel to the surface plane to form solid-state compositions
best described by flattened ‘‘rod-like’’ assemblies with lengths by aggregation of PZn-OAlk-BA building blocks are chronicled in
that vary from 200 nm to 2 mm. Fig. 2c and d and contrast those elucidated for PZn-OAlk-PBA
Structure properties of the solid-state composition engendered
The height profile ranging from 7.5 to 10 nm combined with analogs. As evidenced by Fig. 2c and Fig. S12 (ESI‡), drop-casting
DFT calculation performed on molecular PZn-OAlk-PBA construct PZn-OAlk-BA building blocks from parent DMF solution enforces
(Fig. S26, ESI‡) indicates that 2 to 3 PZn repeating units laterally the formation of nanowires. As indicated by a height profile of 3 to
interact to delineate the multi-layered assembly. The fact 4 nm, [PZn-OAlk-BA]NW nanowires are constructed from one
that initially individualized PZn-OAlk-PBA building blocks porphyrin building block that stacks along a 1D axis. It is worth
spontaneously assemble into materials with a non-negligible noting that this PZn-OAlk-BA superstructure conformation differs
degree of organization validates the non-innocent role played from that elucidated for [PZn-OAlk-PBA]Agg. The fact that PZn-
by the phenyl-derived PBA side chains. The extent to which OAlk-BA units form a single-layered superstructure when drop-
structural properties of solubilized porphyrin precursors impact casted from a DMF solution whereas PZn-OAlk-PBA units organize
solid-state morphology is further unraveled in Fig. 2b that into multi-layered aggregates traces its genesis from the nature of
represents fiber-like materials exclusively constructed from a side chains that flank the identical redox active PZn-OAlk cores.
suspension of supramolecular PZn-OAlk-PBA polymer. The Confirmed by temperature-dependent aggregation experiments
entangled aspect indicates that thinner 1D structures assemble presented earlier, PZn-OAlk-BA building blocks form a super-
by means of hydrophobic interactions to enable the formation structure in toluene solution with spectral signatures that suggest
of mesoscale, hierarchical fibers such as these observed in the existence of J-type aggregates. In agreement with these spectro-
Fig. 2b and Fig. S10 (ESI‡). Considering that the length of a scopic properties, drop-casted supramolecular PZn-OAlk-BA
porphyrin building block is 4.5 nm, the recorded height profile polymer (Fig. 2d) describes a compelling 2D nanostructure by
of 30 to 60 nm suggests that these fibers are composed of 7 to assembling into nanosheets characterized by a height profile of
15 elementary nanowires. The sharp contrast between the 3 nm. This thickness suggests that 2D nanomaterials created in
solid-state morphologies of superstructures that derive from this manner are composed of a monolayer of interacting porphyrin
individualized PZn-OAlk-PBA building blocks and supramolecular building blocks. Please note that the seemingly 1D superstructures
polymer derivative underscores the critical role played by precursor gleaned in Fig. 2 and Fig. S13 (ESI‡) are likely to characterize the
conformation in regulating the structure properties of hierarchical supramolecular polymer precursors which engender formation of
materials.
PZn-OAlk-BA nanosheets upon drop-casting.
J. Mater. Chem. C
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Journal of Materials Chemistry C
Paper
Fig. 4 Summary of the solid-state morphologies delineated by PZn-derived
building blocks and supramolecular polymers.
on a solid-state substrate, these two PZn-derived supramolecular
polymers evolve into higher-ordered fiber-like materials. In contrast,
slipped geometry of J-type aggregate best describes the conformation
of building blocks that comprise PZn-OAlk-BA supramolecular
polymer as suggested by the Kasha model. This aggregate
conformation has a drastic impact during the evaporation of
supramolecular PZn-OAlk-BA polymers as it engenders the
formation of 2D nanosheets. Since PZn-OAlk-BA and PZn-OAlk-
PBA share an identical redox active core, the discrepancy of aggregate
properties originates solely from the structural properties of the PBA
and BA side chains. It is well established that minor structural
modification of the peripheral side chains that flank rigid
p-conjugated cores can enable drastic changes in material
morphologies.63,64 Furthermore, we hypothesize that the difference
Fig. 3 Topographic intermittent contact mode AFM acquired and associated
height profiles recorded for drop-casted: (a) [PZn-OTEG-PBA]Agg aggregates
that originate from individualized PZn-derived building blocks in DMF
solution; (b) [PZn-OTEG-PBA]Fib fibers constructed from parent PZn-
derived supramolecular polymer in toluene solution. For each panel, the
height profile corresponds to the associated numbers on the AFM images.
Design principles have been further explored by modulating of solid-state morphologies observed when comparing [PZn-OAlk-
the amphiphilic character of the PZn core in PZn-OTEG-PBA PBA]Fib and [PZn-OAlk-PBA]NS traces its genesis from the strength of
that features hydrophilic ethylene glycol functional groups and the hydrophobic interactions between supramolecular precursors.
identical hydrophobic PBA side chains to those exploited in With respect to a BA side chain that contains one alkyl functional
PZn-OAlk-PBA. When compared to PZn-OAlk-PBA solid-state group, a PBA unit features two hydrophobic fragments that describe
structure that features a multi-layered ‘‘rod-like’’ morphology, a triangular shape. In addition to the nature of the aggregate that
drop-casted PZn-OTEG-PBA building blocks from DMF solution composes PZn-derived supramolecular polymers, stronger hydro-
assemble into nanowire superstructures captured in Fig. 3a and phobic interaction between PZn-OAlk-PBA and PZn-OTEG-PBA
Fig. S14 (ESI‡). The measured thickness of 2.5–3 nm is diagnostic supramolecular polymers when compared to PZn-OAlk-BA supra-
of one porphyrin unit and indicates that [PZn-OTEG-PBA]NW molecular polymer enables the formation of higher-ordered
superstructure represents an individualized p-stack. To contrast hierarchical materials.
this observation, supramolecular PZn-OTEG-PBA polymer
Aiming to provide molecular benchmarks with which to
engineered by temperature-dependent aggregation in toluene further investigate the impact of side chain properties on final
features rigid-like fibers as presented in Fig. 3b and Fig. S15 superstructure conformation, model compounds PZn-OTEG-Tol
(ESI‡). Similar to the superstructure formed by supramolecular and PZn-OAlk-Tol represented in Scheme 1 were synthesized (see
PZn-OAlk-PBA polymer, [PZn-OTEG-PBA]Fib self-assemblies ESI‡). Please note that these two molecular platforms lack amide
consist of several interacting nanowires as attested by the functions and as such no secondary interactions other than hydro-
recorded height profile of 10 to 25 nm. It is worth noting that phobic interactions are possible. Their solid-sate properties are
on average, [PZn-OTEG-PBA]Fib superstructures are thinner presented in Fig. S16 and S17 (ESI‡). Regardless of the solvent,
than [PZn-OAlk-PBA]Fib, the origin of which can be traced from PZn-OAlk-Tol units exist as individualized building blocks at room
the solubility of respective building blocks.
temperature and describe ‘‘platelets’’ that are 10 to 15 nm thick after
The formation process of PZn-derived superstructures as a drop-casting. Concomitantly, drop-casted PZn-OTEG-Tol building
function of solubilized precursors is summarized in Fig. 4. blocks feature a granular morphology where no distinct hierarchical
Because temperature-dependent aggregation of supramolecular architectures can be evidenced. These findings confirm that in
PZn-OAlk-PBA and PZn-OTEG-PBA polymers reveals the spectro- concert with PZn amphiphilic characters, BA and PBA side chains
scopic fingerprints of H-type aggregates, the conformation of the regulate the morphologies of hierarchical superstructures.
building blocks that construct these p-conjugated superstructures
To glean more insights into the extent to which solid-state
is best described by a co-facial arrangement. During evaporation morphologies elucidated for PZn-derived hierarchical materials
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C

View Article Online
Paper
Journal of Materials Chemistry C
impact their electronic properties, potentiometric data was
acquired for PZn-OAlk-PBA, PZn-OAlk-BA, and PZn-OTEG-PBA
assemblies, and were compared to those of control PZn-OTEG-Tol
and PZn-OAlk-Tol samples. Cyclic voltammetry (CV) measurements
have been performed exploiting working electrodes on which PZn-
based solution has been drop-casted. To ensure reproducibility,
each reported potential corresponds to the average of at least 10
measurements, the most representative cyclic voltammograms
being represented in Fig. 5, 7 and Fig. S18–S25 (ESI‡). For the
sake of clarity, Fig. 6 summarizes the redox potentials of the
PZn-OAlk-derived superstructures. As presented in Fig. 5 and
Fig. S24 (ESI‡), the analysis of CV measurements recorded for
[PZn-OAlk-PBA]Fib, [PZn-OAlk-PBA]Agg, and [PZn-OAlk-Tol]Agg
indicates a minor perturbation of the oxidation potentials as
a function of superstructure conformation. In sharp contrast,
Fig. 6 Diagram that summarizes the recorded oxidation and reduction
potentials as a function of PZn-OAlk-derived superstructure morphologies.
the reduction potentials recorded for these three assemblies from solution-based supramolecular polymers that regulate the
suggest that superstructure conformations considerably impact interaction of porphyrin building blocks whereas nano-aggregates
the potentials required to inject negative charge carriers into originate from assembly of molecularly dissolved building blocks.
their respective conduction bands. The apparent less negative The lower potential at which electrons are injected into the
reduction potential recorded for [PZn-OAlk-PBA]Fib (Eꢀ/0
ꢀ941 mV) when compared to control [PZn-OAlk-Tol]Agg (Eꢀ/0
=
=
conduction band of [PZn-OAlk-PBA]Fib when compared to that
of [PZn-OAlk-PBA]Agg and [PZn-OAlk-Tol]Agg suggests a stronger
ꢀ1010 mV) and [PZn-OAlk-PBA]Agg (Eꢀ/0 = ꢀ1000 mV) indicates electronic coupling between building blocks and may indicate a
that the fiber-like conformation enforces the formation of a higher degree of charge delocalization enforced by the fiber
conduction band that is more stabilized than that evidenced in conformation.
the aggregate derivatives. Such a difference in potentiometric
Electrochemical measurements performed on PZn-OAlk-BA
properties underscores the critical role played by supramolecular solid-state assemblies differ from that recorded for PZn-OAlk-PBA
pathway selection of porphyrin building blocks to modulate compositions and place further emphasis on the structure–function
structure–function properties of hierarchical materials. As high- relationships of supramolecular assemblies. The oxidation and
lighted earlier when discussing self-assembly mechanisms and reduction potentials probed for [PZn-OAlk-BA]NS are chronicled in
solid-state properties, fiber-like domains are exclusively formed Fig. 5c (E0/+ = 780 mV; Eꢀ/0 = ꢀ1030 mV) and appear more positive
Fig. 5 Cyclic voltammetry measurements that chronicle the anodic and cathodic redox processes of (porphinato)zinc(II) superstructures drop-casted
on a glassy carbon working electrode: (a) PZn-OAlk-PBA fibers from supramolecular polymer precursors, (b) PZn-OAlk-PBA nanoaggregates from
individualized building blocks, (c) PZn-OAlk-BA nanosheets from supramolecular precursors, and (d) PZn-OAlk-BA nanowires from individualized
building blocks. The blue lines correspond to the tangents used to measure the onset potentials. All measurements are being reported against sodium
calomel electrode (SCE) using Fc/Fc+ as an internal potentiometric standard Fc/Fc+ = 0.40 V vs. SCE in acetonitrile. Experimental conditions: 0.1 M TBAP,
scan rate = 100 mV sꢀ1, glassy carbon electrode, Ag/AgCl reference electrode. To ensure reproducibility, all the presented measurements have been
recorded from different batches. Additional CV measurements are reported in Fig. S18–S21 (ESI‡).
J. Mater. Chem. C
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Journal of Materials Chemistry C
Paper
comparing the electronic structures of nanosheets, fibers, and
nanowire superstructures, we postulate that these self-assembly
conformations do not perturb the interaction of PZn HOMO
with a magnitude that can be detected by CV measurements. In
contrast, the fact that a less negative potential can be utilized to
inject electrons into the conduction band of PZn-OAlk-BA
nanowires with respect to that of PZn-OAlk-BA nano-
sheets may be diagnostic of a larger degree of electronic
coupling between the PZn LUMOs in 1D assemblies than in
2D superstructures.
It is also worth noting the drastic difference of reduction
potential when comparing [PZn-OAlk-BA]NW (Eꢀ/0 = ꢀ650 mV)
and [PZn-OAlk-PBA]Fib (Eꢀ/0 = ꢀ965 mV). Because PZn-OAlk-
derived fiber and nanowire superstructures share identical
redox active PZn subunits and comparable solid-state morphologies
(both are 1D materials), the evident discrepancy when comparing
the potentiometric properties of these two self-assemblies cannot be
solely attributed to a perturbation of porphyrin–porphyrin electronic
interaction. Rather, we believe that the more negative potential
required to inject electrons into the [PZn-OAlk-PBA]Fib conduction
band when compared to [PZn-OAlk-BA]NW may trace its genesis
from a screening effect. As evidenced by AFM investigation, fibers
built from PZn-OAlk-PBA building blocks feature a thickness
ranging from 30 nm to 60 nm. Considering that the length of
one PZn repeating unit is 4.5 nm, these fibers are composed of
7 to 14 entangled nanowires. Consequently, initially injected
electrons at less negative potentials may screen the injection of
Fig. 7 Cyclic voltammetry measurements that chronicle the anodic and
cathodic redox processes of (porphinato)zinc(II) superstructures drop-
casted on a glassy carbon working electrode: (a) PZn-OTEG-PBA nano-
wire from individualized building blocks, (b) PZn-OTEG-PBA fiber from
supramolecular polymer. The blue lines correspond to the tangents used
to measure the onset potentials. All measurements are being reported
against sodium calomel electrode (SCE) using Fc/Fc+ as an internal
potentiometric standard Fc/Fc+ = 0.40 V vs. SCE in acetonitrile. Experi-
mental conditions: 0.1 M TBAP, scan rate = 100 mV sꢀ1, glassy carbon
electrode, Ag/AgCl reference electrode. To ensure reproducibility, all the
presented measurements have been recorded from different batches.
Additional CV measurements are reported in Fig. S22 and S23 (ESI‡).
(E0/+ = +65 mV) and more negative (Eꢀ/0 = ꢀ89 mV) than that additional charges therefore imposing the use of a more negative
elucidated for [PZn-OAlk-PBA]Fib. The fact that [PZn-OAlk-PBA]Fib potential to fully reduce the entire superstructure. Please note that
conformation promotes the formation of valence and conduction the screening effect in multi-layered semiconducting materials is a
bands that are destabilized and stabilized with respect to those well-established electronic phenomenon that notoriously perturbs
formed in [PZn-OAlk-BA]NS traces its genesis from the properties of investigation of charge transport properties in field-effect
the aggregates that comprise these superstructures.
transistors.65–67
Congruent with the optical properties evidenced by [PZn-
Potentiometric data recorded for PZn-OTEG-PBA superstructures
OAlk-BA]NS, J-type aggregates best describe this self-assembled are presented in Fig. 7 and confirm initial structure–function
superstructure and suggest a lesser degree of frontier molecular relationships elucidated for PZn-OAlk-derived hierarchical materials.
orbital (FMO) overlap when compared to H-type aggregates that To facilitate the discussion, all redox potentials recorded for
24–26
construct [PZn-OAlk-PBA]Fib
.
Consequently, lower potentials PZn-OTEG-derived superstructures are summarized in Fig. 8.
are required to inject charges into fiber-like superstructure with a When compared to electrochemical measurements performed
conformation that promotes stronger electronic coupling between on PZn-OTEG-Tol control sample (Fig. S25, ESI;‡ E0/+ = 600 mV;
repeating units. This assumption is further confirmed when
E
ꢀ/0 = ꢀ1000 mV), lower cathodic (Eꢀ/0 = ꢀ950 mV) and anodic
comparing the potentiometric properties of [PZn-OAlk-BA]NW potentials (E0/+ = 540 mV) are necessary to inject electrons and
and [PZn-OAlk-BA]NS presented in Fig. 5c and d. Nanowires holes into the conduction and valence bands of [PZn-OTEG-
formed by drop-casting a DMF solution of PZn-OAlk-BA building PBA]Fib superstructures. Furthermore, the fact that the elementary
blocks manifest a reduction potential (Eꢀ/0 = ꢀ650 mV) less negative nanowires that construct [PZn-OTEG-PBA]Fib superstructures can
by more than 350 mV when compared to [PZn-OAlk-BA]NS. The be formed by drop-casting individualized PZn-OTEG-PBA building
apparent stabilization of the conduction band energy observed in blocks from a DMF solution provides samples with which
[PZn-OAlk-BA]NW points toward the non-innocent role played to unambiguously probe the potentiometric properties of a
by the aggregate properties. Building block conformation in a fundamental p-stack. Mimicking the structure–function properties
J-type aggregate is best described by a slipped geometry that unveiled for PZn-OAlk-derived nanowires and fibers, potentio-
while enforcing coupling of the transition dipole moment, reduces metric data recorded for [PZn-OTEG-PBA]NW underscore a drastic
FMO overlaps. In contrast, cofacial geometry that describes con- decrease of the reduction potential (E0/+ = ꢀ630 mV) when
formation of H-type aggregates can enforce stronger interaction of compared to [PZn-OTEG-PBA]Fib (E0/+ = ꢀ950 mV) while only a
the FMO between adjacent building blocks and may favour a minor perturbation of the oxidation potentials can be appreciated.
higher degree of charge delocalization. Because only a minor The apparent less negative potential required to inject negative
perturbation of the valence band energies can be gleaned when charge carriers into [PZn-OTEG-PBA]NW conduction band when
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C

View Article Online
Paper
Journal of Materials Chemistry C
of parent solubilized precursors. The panoply of superstructure
conformation has allowed us to systematically investigate the
potentiometric data of these hierarchical semiconducting
materials and establish the energy level of the conduction
and valence bands with respect to the SCE reference electrode.
A general trend emerges: while superstructure conformation
modestly perturbs the energies of valence bands across the
PZn-OTEG and PZn-OAlk series, a drastic change of conduction
band energies can be deciphered. For identical redox-active
cores and comparable superstructure morphologies, the less
negative potential required to reduce PZn-derived nanowires
when compared to PZn-derived fibers indicates that the electronic
properties of the fundamental p-stacks constructing higher
ordered hierarchical objects can exclusively be assessed when
probing nanowires at the individualized levels. Furthermore,
the fact that 2D PZn-OAlk-BA nanosheets built from a single-
Fig. 8 Diagram that compares the recorded oxidation and reduction
potentials as a function of PZn-OTEG-derived and relevant PZn-OAlk-
relevant superstructure morphologies.
compared to [PZn-OTEG-PBA]Fib supports our initial hypothesis
that: (1) screening effect in higher-order hierarchical materials may
plague the accurate assessment of the potentiometric properties
that characterize elementary constituent, and (2) electrochemical
measurements exclusively performed on elementary nanowire can
provide reliable potentials with which to assess valence and
conduction band energies of fundamental p-stacks (Fig. 8).
In addition, comparing the oxidation and reduction potentials
recorded for [PZn-OTEG-Tol]Agg and [PZn-OTEG-PBA]NW provides
important insight onto the structure–function properties of
p-conjugated superstructures. Relative to [PZn-OTEG-Tol]Agg, the
apparent less negative potential (Eꢀ/0 = ꢀ630 mV) required to
inject negative charge carriers into the conduction band of
[PZn-OTEG-PBA]NW indicates a superstructure conformation that
enforces stronger electronic coupling between porphyrin repeating
units. The fact that only a minor perturbation of the oxidation
potential can be detected across [PZn-OTEG-PBA]NW, [PZn-
OTEG-PBA]Fib, and [PZn-OTEG-PBA]Agg suggests that super-
structure conformation plays a minor role in mixing the HOMO
energy level of porphyrin repeating units but, in contrast,
enforces a non-negligible interaction between the LUMO energy
level of PZn building blocks the magnitude of which can be
detected by CV measurements.
layer of interacting (porphinato)zinc(II) units evidences
a
reduction potential destabilized by more than 350 mV when
compared to that of PZn-OAlk-BA nanowires may differentiate
the role played by J- and H-type aggregates in dictating the
potentiometric properties of final superstructures. Because this
work demonstrates that electronic properties of p-conjugated
supramolecular polymers and related superstructures can be
probed using conventional cyclic voltammetry experiments, we
posit that electrochemical methods will expand the tool box to
scrutinize structure–function relationships of self-assembled
hierarchical materials and will shed new light on their electronic
properties.
Experimental
Materials and instrumentation
All water-sensitive and oxygen-sensitive compounds were stored
and handled in a Braun Labmaster DP glovebox. Standard Schlenk
techniques were employed to manipulate water-sensitive and
oxygen-sensitive reactions. Only ultrapure argon purchased from
Airgas was used. All deuterated solvents were purchased from
Cambridge Isotope Laboratories, Inc. Methanol, ethanol, hexane,
acetone, chloroform, dichloromethane, toluene, N,N-dimethyl-
formamide (DMF), tetrahydrofuran (THF), sodium chloride and
silica gel (70–90 mm) were purchased from VWR International. All
Conclusions
In summary, we have reported the synthesis, characterization distilled THF was prepared under argon from a sodium/benzo-
and self-assembly properties of novel (porphinato)zinc(II) building phenone distillation device. Sodium sulfate, sodium chloride,
blocks. Modification of the side chain structures that flank potassium carbonate, diisopropylamine, tetrabutylammonium
PZn-redox active cores enables controlling the conformation of fluoride (1 M solution in THF) and tetrabutylammonium hexa-
hierarchical materials with structure–function relationships fluorophosphate were purchased from Sigma-Aldrich. Copper(I)
that have been unveiled for the first time by cyclic voltammetry iodide, sodium, benzophenone, (triisopropylsilyl)acetylene and
experiments. As evidenced by a systematic AFM investigation, propargylamine were purchased from Alfa Aesar. Dodecanoyl
while solubilized PZn-OTEG-PBA and PZn-OAlk-BA building chloride, 1,4-dibromobenzene, N,N-dimethylpyridin-4-amine and
blocks form 1D nanowires through drop-casting deposition, N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide hydrochloride
their respective solution-based supramolecular polymer precursors were purchased from Tokyo Chemical Industry Co., Ltd. Tetrakis-
provide formation of fiber-like materials and 2D nanosheets in the (triphenylphosphine)palladium(0) was purchased from Strem
solid state. The evidenced discrepancy when monitoring super- Chemicals. Size exclusion chromatography was performed using
structure morphologies underscores the cardinal role played not Bio-Beads S-X1 Support purchased from Bio-Rad Laboratories, Inc.
only by processing conditions but also by the structural properties Nuclear magnetic resonance (NMR) spectroscopy was performed
J. Mater. Chem. C
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Journal of Materials Chemistry C
Paper
on a Bruker Avance 400 MHz NMR spectrometer. Ultraviolet-visible solid (0.041 g, 21%). 1H NMR (400 MHz, THF-D8 with two drops
(UV-Vis) spectrophotometry was performed on a Cary 5000 of CDCl3 and one drop of pyridine-D5, 333 K) d = 9.70 (d, 4H,
UV-Vis-NIR spectrophotometer. Fourier-transform infrared J = 4.0 Hz), 9.47 (d, 4H, J = 4.4 Hz), 8.24 (br, 4H), 8.04 (s, 4H), 5.15
(FTIR) spectroscopy was performed on a PerkinElmer Frontier (t, 4H, J = 8.0 Hz), 4.39 (t, 4H, J = 7.4 Hz), 3.55 (t, 4H, J = 6.0 Hz),
FTIR spectrometer. Cyclic voltammetry (CV) was performed on a 2.45 (t, 8H, J = 7.2 Hz), 2.24 (s, 6H), 2.2–1.0 (m, 82H), 1.0–0.8 (m,
PARSTAT 3000A potentiostat/galvanostat/EIS analyzer. Electro- 36H) ppm. MALDI-MS m/z: 1730.04 ([M + H]+, calcd for 1730.18).
spray ionization mass spectrometry (ESI-MS) was performed on Note: because of the low solubility of this compound, there were
a Bruker MicroQ-TOF III ESI mass spectrometer. Matrix-assisted not enough signals when 13C NMR was performed.
laser desorption/ionization mass spectrometry (MALDI-MS) was
(5,15-Bis{2-[4-(4,8-diaza-5,9-dioxoicosynyl)phenyl]ethynyl}-10,
performed on a Bruker Autoflex III MALDI mass spectrometer. 20-bis[2-(3,5,5-trimethylhexyloxy)ethyl]porphinato)zinc(II) PZn-
Atomic force microscopy (AFM) was performed on an Agilent OAlk-BA. The synthetic pathway is presented in Scheme S4
5420 AFM/SPM microscope. Silicon wafers (0.5 mm) used to (ESI‡). {5,15-Dibromo-10,20-bis[2-(3,5,5-trimethylhexyloxy)ethyl]-
prepare AFM samples were purchased from UniversityWafer, Inc. porphinato}zinc(II) (18, Scheme S4, ESI‡) (0.0750 g, 8.60 ꢁ
10ꢀ5 mol), 4-aza-N-[3-(4-ethynylphenyl)prop-2-ynyl]-5-oxododec-
anamide (7, Scheme S4, ESI‡) (0.110 g, 2.69 ꢁ 10ꢀ4 mol), CuI
AFM sample preparation
Silicon wafers were soaked in ethanol for 1 h and washed with (1.10 mg, 5.78 ꢁ 10ꢀ6 mol) and Pd(PPh3)4 (7.00 mg, 6.06 ꢁ
acetone. Porphyrin solutions that had undergone corresponding 10ꢀ6 mol) were added into a Schlenk flask in a glove box. After 50
temperature ramping UV-Vis experiments were drop-casted onto mL of distilled THF and 10 mL of dry (Me2CH)2NH were mixed,
the wafers. When no solvent droplets were visible, the wafers freeze–pump–thawed and cannulated into the Schlenk flask, the
were dried under vacuum.
reaction mixture was stirred at 60 1C for 12 h under Ar and passed
through a silica plug using THF as the eluent. After solvent removal,
the residue was chromatographed first on silica using 20 : 1 CHCl3 :
CV measurements
A glassy carbon working electrode, a platinum counter electrode CH3OH as the eluent and then on a size exclusion column using
and a Ag/AgCl (3 M NaCl) reference electrode were used. The THF as the eluent. The collected solid was washed with CH3OH and
ferrocene/ferrocenium redox couple was used as an internal dried under vacuum to give the desired product as a green solid
potentiometric standard. Measurements were performed using (0.020 g, 15%). 1H NMR (400 MHz, CDCl3 with a drop
tetrabutylammonium hexafluorophosphate (0.1 M) as the electro- of pyridine-D5) d = 9.69 (d, 4H, J = 4.4 Hz), 9.47 (d, 4H, J =
lyte in distilled acetonitrile under argon. Porphyrin solutions 4.8 Hz), 7.96 (d, 4H, J = 8.0 Hz), 7.61 (d, 4H, J = 8.4 Hz), 6.31 (br,
that had undergone corresponding temperature ramping UV-Vis 2H), 6.25 (br, 2H), 5.17 (t, 4H, J = 7.4 Hz), 4.41 (t, 4H, J = 7.6 Hz),
experiments were drop-casted onto the electrode (7 ꢁ 50 mL) and 4.38 (d, 4H, J = 5.2 Hz), 3.60 (q, 4H, J = 6.4 Hz), 3.59 (t, 4H, J =
dried under vacuum. For each sample, cathodic and anodic cycles 6.4 Hz), 2.53 (t, 4H, J = 6.2 Hz), 2.19 (t, 4H, J = 7.8 Hz), 2.0–1.0 (m,
(0.1 V sꢀ1 for both) were scanned separately, and each cycle was 46H), 1.0–0.8 (m, 30H) ppm. 13C NMR (101 MHz, CDCl3 with a drop
repeated for three times with the average oxidation/reduction of pyridine-D5) d = 173.6, 171.4, 151.2, 150.4, 132.0, 131.3, 131.1,
potentials taken. Upon determination of the oxidation/reduction 129.4, 124.6, 122.1, 117.6, 99.7, 95.7, 95.5, 86.6, 83.4, 77.2, 69.7,
potentials, the onset points were taken where the current started to 51.2, 39.2, 36.9, 35.9, 35.6, 35.3, 31.9, 31.1, 30.1, 30.0, 29.6, 29.6,
deviate from the baseline.
29.5, 29.4, 29.3, 29.3, 26.2, 25.8, 22.8, 22.7, 14.1 ppm. MALDI-MS
(5,15-Bis{2-[3,5-bis(dodecanoylamino)-4-methylphenyl]ethynyl}- m/z: 1526.82 ([M + H]+, calcd for 1526.91).
10,20-bis[2-(3,5,5-trimethylhexyloxy)ethyl]porphinato)zinc(II) PZn-
[5,15-Bis{2-[3,5-bis(dodecanoylamino)-4-methylphenyl]ethynyl}-
OAlk-PBA. The synthetic pathway is presented in Scheme S5 10,20-bis(3,5-bis{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}phenyl)-
(ESI‡). {5,15-Dibromo-10,20-bis[2-(3,5,5-trimethylhexyloxy)ethyl]- porphinato]zinc(II) PZn-OTEG-PBA. The synthetic pathway is
porphinato}zinc(II) (18) (0.100 g, 1.15 ꢁ 10ꢀ4 mol), N,N0-(5- presented in Scheme S7 (ESI‡). [5,15-Bis(3,5-bis{2-[2-(2-methoxy-
ethynyl-2-methyl-1,3-phenylene)didodecanamide (12) (0.200 g, ethoxy)ethoxy]ethoxy}phenyl)-10,20-dibromoporphinato]zinc(II)
3.92 ꢁ 10ꢀ4 mol), CuI (2.20 mg, 1.16 ꢁ 10ꢀ5 mol) and Pd(PPh3)4 (23) (0.0900 g, 6.75 ꢁ 10ꢀ5 mol), N,N0-(5-ethynyl-2-methyl-1,3-
(20.0 mg, 1.73 ꢁ 10ꢀ5 mol) were added into a Schlenk flask in a phenylene)didodecanamide (12) (0.104 g, 2.04 ꢁ 10ꢀ4 mol), CuI
glove box. After 60 mL of distilled THF and 15 mL of dry (1.30 mg, 6.83 ꢁ 10ꢀ6 mol) and Pd(PPh3)4 (11.0 mg, 9.52 ꢁ
(Me2CH)2NH were mixed, freeze–pump–thawed and cannulated 10ꢀ6 mol) were added into a Schlenk flask in a glove box. After
into the Schlenk flask, the reaction mixture was stirred at 60 1C for 50 mL of distilled THF and 10 mL of dry (Me2CH)2NH were
12 h under Ar. After solvent removal, the solid was dispersed in mixed, freeze–pump–thawed and cannulated into the Schlenk
100 mL of THF, and the mixture was refluxed for 30 min and flask, the reaction mixture was stirred at 60 1C for 12 h under Ar
filtered. The above operation was repeated for seven times (a and passed through a silica plug using THF as the eluent. After
Soxhlet extractor can be used as well for better efficiency). All solvent removal, the residue was chromatographed first on
filtrate was combined and the solvent was evaporated. The silica using 10 : 1 CHCl3 : CH3OH as the eluent and then on a
resulting solid was dispersed in the mixture of 40 mL of CH3OH size exclusion column using THF as the eluent. The collected
and 40 mL of THF, and the mixture was refluxed for 30 min and solid was washed with CH3OH and dried under vacuum to
cooled to room temperature. After filtration, the collected solid give the desired product as a green solid (0.057 g, 39%).
was dried under vacuum to give the desired product as a green 1H NMR (400 MHz, CDCl3 with a drop of pyridine-D5) d = 9.64
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C

View Article Online
Paper
Journal of Materials Chemistry C
7 J. H. Olivier, J. Park, P. Deria, J. Rawson, Y. Bai, S. Kumbhar
Amar and J. Therien Michael, Unambiguous Diagnosis of
Photoinduced Charge Carrier Signatures in a Stoichio-
metrically Controlled Semiconducting Polymer-Wrapped
Carbon Nanotube Assembly, Angew. Chem., Int. Ed., 2015,
54, 8133–8138.
8 P. Gawrys, D. Boudinet, A. Kornet, D. Djurado, S. Pouget,
J.-M. Verilhac, M. Zagorska and A. Pron, Organic semi-
conductors for field-effect transistors (FETs): tuning of
spectroscopic, electrochemical, electronic and structural
properties of naphthalene bisimides via substituents containing
alkylthienyl moieties, J. Mater. Chem., 2010, 20, 1913–1920.
9 H. Ma, N. Liu and J.-D. Huang, A DFT Study on the Electronic
Structures and Conducting Properties of Rubrene and its Deriva-
tives in Organic Field-Effect Transistors, Sci. Rep., 2017, 7, 331.
10 K. Xiao, Y. Liu, T. Qi, W. Zhang, F. Wang, J. Gao, W. Qiu,
Y. Ma, G. Cui, S. Chen, X. Zhan, G. Yu, J. Qin, W. Hu and
D. Zhu, A Highly p-Stacked Organic Semiconductor for Field-
Effect Transistors Based on Linearly Condensed Pentathieno-
acene, J. Am. Chem. Soc., 2005, 127, 13281–13286.
(d, 4H, J = 4.4 Hz), 8.90 (d, 4H, J = 4.8 Hz), 8.07 (br, 4H), 7.43 (br,
4H), 7.37 (d, 4H, J = 2.0 Hz), 6.95 (t, 2H, J = 2.0 Hz), 4.33 (t, 8H, J =
4.8 Hz), 3.96 (t, 8H, J = 4.8 Hz), 3.79 (m, 8H), 3.71 (m, 8H), 3.64
(m, 8H), 3.50 (m, 8H), 3.32 (s, 12H), 2.49 (t, 8H, J = 6.8 Hz), 2.24
(s, 6H), 2.0–1.0 (m, 72H), 0.87 (t, 12H, J = 5.8 Hz) ppm. 13C NMR
(101 MHz, CDCl3 with a drop of pyridine-D5) d = 172.1, 157.8,
151.8, 149.5, 144.5, 136.5, 132.3, 130.7, 127.3, 125.6, 124.6,
122.5, 121.9, 114.9, 101.0, 95.5, 93.6, 71.9, 70.9, 70.7, 70.5,
69.9, 67.8, 59.0, 37.2, 31.9, 29.6, 29.6, 29.6, 29.5, 29.4, 29.3,
29.3, 25.8, 22.6, 14.1 ppm. MALDI-MS m/z: 2191.27 ([M + H]+,
calcd for 2191.27).
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was made possible by The University of Miami
Startup Fund. The authors thank Prof. Roger Leblanc for his
assistance with atomic force microscopy.
11 V. Coropceanu, J. Cornil, D. A. da Silva Filho, Y. Olivier,
´
R. Silbey and J.-L. Bredas, Charge Transport in Organic
Semiconductors, Chem. Rev., 2007, 107, 926–952.
12 M. Mas-Torrent and C. Rovira, Role of Molecular Order and
Solid-State Structure in Organic Field-Effect Transistors,
Chem. Rev., 2011, 111, 4833–4856.
Notes and references
13 S. Pramanik, C. G. Stefanita, S. Patibandla, S. Bandyopadhyay,
K. Garre, N. Harth and M. Cahay, Observation of extremely long
spin relaxation times in an organic nanowire spin valve, Nat.
Nanotechnol., 2007, 2, 216.
14 K. Michaeli, N. Kantor-Uriel, R. Naaman and D. H. Waldeck,
The electron’s spin and molecular chirality – how are they
related and how do they affect life processes?, Chem. Soc.
Rev., 2016, 45, 6478–6487.
15 W. Mtangi, F. Tassinari, K. Vankayala, A. Vargas Jentzsch,
B. Adelizzi, A. R. A. Palmans, C. Fontanesi, E. W. Meijer and
R. Naaman, Control of Electrons’ Spin Eliminates Hydrogen
Peroxide Formation During Water Splitting, J. Am. Chem.
Soc., 2017, 139, 2794–2798.
1 T. Hasobe, K. Saito, P. V. Kamat, V. Troiani, H. Qiu, N. Solladie,
K. S. Kim, J. K. Park, D. Kim, F. D’Souza and S. Fukuzumi,
Organic solar cells. Supramolecular composites of porphyrins
and fullerenes organized by polypeptide structures as light
harvesters, J. Mater. Chem., 2007, 17, 4160–4170.
2 V. V. Roznyatovskiy, R. Carmieli, S. M. Dyar, K. E. Brown and
M. R. Wasielewski, Photodriven Charge Separation and
Transport in Self-Assembled Zinc Tetrabenzotetraphenyl-
porphyrin and Perylenediimide Charge Conduits, Angew.
Chem., Int. Ed., 2014, 53, 3457–3461.
3 P.-O. Schwartz, L. Biniek, E. Zaborova, B. Heinrich,
´
M. Brinkmann, N. Leclerc and S. Mery, Perylenediimide-
Based Donor–Acceptor Dyads and Triads: Impact of
Molecular Architecture on Self-Assembling Properties, J. Am.
Chem. Soc., 2014, 136, 5981–5992.
´
16 V. Kiran, P. Mathew Shinto, R. Cohen Sidney, I. Hernandez
Delgado, J. Lacour and R. Naaman, Helicenes—A New Class
of Organic Spin Filter, Adv. Mater., 2016, 28, 1957–1962.
4 N. J. Hestand, R. V. Kazantsev, A. S. Weingarten, L. C. Palmer,
S. I. Stupp and F. C. Spano, Extended-Charge-Transfer Excitons 17 K. E. Martin, Z. Wang, T. Busani, R. M. Garcia, Z. Chen,
in Crystalline Supramolecular Photocatalytic Scaffolds, J. Am.
Chem. Soc., 2016, 138, 11762–11774.
5 A. T. Haedler, K. Kreger, A. Issac, B. Wittmann, M. Kivala,
Y. Jiang, Y. Song, J. L. Jacobsen, T. T. Vu, N. E. Schore,
B. S. Swartzentruber, C. J. Medforth and J. A. Shelnutt,
Donor–Acceptor Biomorphs from the Ionic Self-Assembly
of Porphyrins, J. Am. Chem. Soc., 2010, 132, 8194–8201.
¨
N. Hammer, J. Kohler, H.-W. Schmidt and R. Hildner, Long-
´
range energy transport in single supramolecular nanofibres 18 J.-L. Bredas, J. E. Norton, J. Cornil and V. Coropceanu,
at room temperature, Nature, 2015, 523, 196.
Molecular Understanding of Organic Solar Cells: The Chal-
¨
6 L. F. Dossel, V. Kamm, I. A. Howard, F. Laquai, W. Pisula,
lenges, Acc. Chem. Res., 2009, 42, 1691–1699.
X. Feng, C. Li, M. Takase, T. Kudernac, S. De Feyter and 19 E. Moulin, J.-J. Cid and N. Giuseppone, Advances in Supra-
K. Mu¨llen, Synthesis and Controlled Self-Assembly of
Covalently Linked Hexa-peri-hexabenzocoronene/Perylene
Diimide Dyads as Models To Study Fundamental Energy
molecular Electronics – From Randomly Self-assembled
Nanostructures to Addressable Self-Organized Interconnects,
Adv. Mater., 2013, 25, 477–487.
and Electron Transfer Processes, J. Am. Chem. Soc., 2012, 20 A. K. Thazhathveetil, M. A. Harris, R. M. Young, M. R.
134, 5876–5886.
Wasielewski and F. D. Lewis, Efficient Charge Transport
J. Mater. Chem. C
This journal is ©The Royal Society of Chemistry 2018

View Article Online
Journal of Materials Chemistry C
Paper
via DNA G-Quadruplexes, J. Am. Chem. Soc., 2017, 139, 36 T. Fukui, S. Kawai, S. Fujinuma, Y. Matsushita, T. Yasuda,
1730–1733.
T. Sakurai, S. Seki, M. Takeuchi and K. Sugiyasu, Control
over differentiation of a metastable supramolecular assembly
in one and two dimensions, Nat. Chem., 2016, 9, 493.
21 M. Kastler, W. Pisula, F. Laquai, A. Kumar, R. J. Davies,
´
S. Baluschev, M. C. Garcia-Gutierrez, D. Wasserfallen,
H. J. Butt, C. Riekel, G. Wegner and K. Mu¨llen, Organization 37 S. Ogi, C. Grzeszkiewicz and F. Wurthner, Pathway complexity in
of Charge-Carrier Pathways for Organic Electronics, Adv.
Mater., 2006, 18, 2255–2259.
22 K. Liu, A. Levy, C. Liu and J.-H. Olivier, Tuning Structure–
the self-assembly of a zinc chlorin model system of natural
bacteriochlorophyll J-aggregates, Chem. Sci., 2018, 9,
2768–2773.
Function Properties of p-Conjugated Superstructures by Redox- 38 R. van der Weegen, J. P. Teunissen Abraham and E. W. Meijer,
Assisted Self-Assembly, Chem. Mater., 2018, 30, 2143–2150.
23 O. Ostroverkhova, Organic Optoelectronic Materials: Mechanisms
and Applications, Chem. Rev., 2016, 116, 13279–13412.
24 F. C. Spano and C. Silva, H- and J-Aggregate Behavior in Polymeric
Semiconductors, Annu. Rev. Phys. Chem., 2014, 65, 477–500.
25 N. J. Hestand and F. C. Spano, Molecular Aggregate Photo-
Directing the Self-Assembly Behaviour of Porphyrin-Based
Supramolecular Systems, Chem. – Eur. J., 2017, 23, 3773–3783.
39 W. Wagner, M. Wehner, V. Stepanenko, S. Ogi and F. Wu¨rthner,
Living Supramolecular Polymerization of a Perylene Bisimide
Dye into Fluorescent J-Aggregates, Angew. Chem., Int. Ed., 2017,
56, 16008–16012.
physics beyond the Kasha Model: Novel Design Principles 40 S. Ogi, V. Stepanenko, K. Sugiyasu, M. Takeuchi and F. Wu¨rthner,
for Organic Materials, Acc. Chem. Res., 2017, 50, 341–350.
26 N. J. Hestand and F. C. Spano, Expanded Theory of H- and
J-Molecular Aggregates: The Effects of Vibronic Coupling
Mechanism of Self-Assembly Process and Seeded Supramolecular
Polymerization of Perylene Bisimide Organogelator, J. Am. Chem.
Soc., 2015, 137, 3300–3307.
and Intermolecular Charge Transfer, Chem. Rev., 2018, 118, 41 Z. Xie, B. Xiao, Z. He, W. Zhang, X. Wu, H. Wu, F. Wurthner,
7069–7163.
C. Wang, F. Xie, L. Liu, Y. Ma, W.-Y. Wong and Y. Cao, Self-
assembled perylene bisimide J-aggregates as promising
cathode modifiers for highly efficient inverted polymer solar
cells, Mater. Horiz., 2015, 2, 514–518.
27 J. Vura-Weis, M. A. Ratner and M. R. Wasielewski, Geometry
and Electronic Coupling in Perylenediimide Stacks:
Mapping StructureꢀCharge Transport Relationships, J. Am.
Chem. Soc., 2010, 132, 1738–1739.
28 Supramolecular Materials for Opto-Electronics, ed. N. Kock,
Royal Chemical Society, 2014, pp. P001–P369.
42 J. Gershberg, F. Fennel, T. H. Rehm, S. Lochbrunner and
F. Wurthner, Anti-cooperative supramolecular polymerization:
a new K2-K model applied to the self-assembly of perylene
bisimide dye proceeding via well-defined hydrogen-bonded
dimers, Chem. Sci., 2016, 7, 1729–1737.
´
29 G. Fernandez, M. Stolte, V. Stepanenko and F. Wu¨rthner,
Cooperative Supramolecular Polymerization: Comparison
¨
of Different Models Applied on the Self-Assembly of Bis- 43 F. Wu¨rthner, C. R. Saha-Moller, B. Fimmel, S. Ogi,
(merocyanine) Dyes, Chem. – Eur. J., 2012, 19, 206–217.
30 M. M. J. Smulders, A. P. H. J. Schenning and E. W. Meijer,
Insight into the Mechanisms of Cooperative Self-Assembly:
P. Leowanawat and D. Schmidt, Perylene Bisimide Dye
Assemblies as Archetype Functional Supramolecular Materials,
Chem. Rev., 2016, 116, 962–1052.
The ‘‘Sergeants-and-Soldiers’’ Principle of Chiral and Achiral 44 P. Lova, V. Grande, G. Manfredi, M. Patrini, S. Herbst,
C3-Symmetrical Discotic Triamides, J. Am. Chem. Soc., 2008,
130, 606–611.
31 D. Zhao and J. S. Moore, Nucleation–elongation: a mechanism
F. Wu¨rthner and D. Comoretto, All-Polymer Photonic Micro-
cavities Doped with Perylene Bisimide J-Aggregates, Adv.
Opt. Mater., 2017, 5, 1700523.
´
for cooperative supramolecular polymerization, Org. Biomol. 45 C. Kaufmann, W. Kim, A. Nowak-Krol, Y. Hong, D. Kim and
Chem., 2003, 1, 3471–3491.
F. Wu¨rthner, Ultrafast Exciton Delocalization, Localization,
and Excimer Formation Dynamics in a Highly Defined
Perylene Bisimide Quadruple p-Stack, J. Am. Chem. Soc.,
2018, 140, 4253–4258.
32 F. Tantakitti, J. Boekhoven, X. Wang, R. V. Kazantsev, T. Yu,
J. Li, E. Zhuang, R. Zandi, J. H. Ortony, C. J. Newcomb,
L. C. Palmer, G. S. Shekhawat, M. O. de la Cruz, G. C. Schatz
´
and S. I. Stupp, Energy landscapes and functions of supra- 46 J. Sung, A. Nowak-Krol, F. Schlosser, B. Fimmel, W. Kim,
molecular systems, Nat. Mater., 2016, 15, 469.
D. Kim and F. Wu¨rthner, Direct Observation of Excimer-
Mediated Intramolecular Electron Transfer in a Cofacially-
Stacked Perylene Bisimide Pair, J. Am. Chem. Soc., 2016, 138,
9029–9032.
33 M. J. Smulders Maarten, M. L. Nieuwenhuizen Marko,
F. A. de Greef Tom, P. van der Schoot, P. H. J. Schenning
Albertus and E. W. Meijer, How to Distinguish Isodesmic
from Cooperative Supramolecular Polymerisation, Chem. – 47 J. Sung, P. Kim, B. Fimmel, F. Wu¨rthner and D. Kim, Direct
Eur. J., 2009, 16, 362–367.
observation of ultrafast coherent exciton dynamics in helical
p-stacks of self-assembled perylene bisimides, Nat. Commun.,
2015, 6, 8646.
34 S. Ogi, K. Sugiyasu, S. Manna, S. Samitsu and M. Takeuchi,
Living supramolecular polymerization realized through a
biomimetic approach, Nat. Chem., 2014, 6, 188.
35 T. Fukui, M. Takeuchi and K. Sugiyasu, Autocatalytic
Time-Dependent Evolution of Metastable Two-Component
Supramolecular Assemblies to Self-Sorted or Coassembled
State, Sci. Rep., 2017, 7, 2425.
48 A. Nowak-Krol, B. Fimmel, M. Son, D. Kim and F. Wurthner,
Photoinduced electron transfer (PET) versus excimer for-
mation in supramolecular p/n-heterojunctions of perylene
bisimide dyes and implications for organic photovoltaics,
Faraday Discuss., 2015, 185, 507–527.
This journal is ©The Royal Society of Chemistry 2018
J. Mater. Chem. C

View Article Online
Paper
Journal of Materials Chemistry C
49 B. M. Savoie, N. E. Jackson, L. X. Chen, T. J. Marks and 58 S. Mathew, A. Yella, P. Gao, R. Humphry-Baker, B. F. E. Curchod,
M. A. Ratner, Mesoscopic Features of Charge Generation in
Organic Semiconductors, Acc. Chem. Res., 2014, 47, 2545–2557.
50 P. Deria, J.-H. Olivier, J. Park and M. J. Therien, Potentio-
metric, Electronic, and Transient Absorptive Spectroscopic
N. Ashari-Astani, I. Tavernelli, U. Rothlisberger, M. K. Nazeeruddin
¨
and M. Gratzel, Dye-sensitized solar cells with 13% efficiency
achieved through the molecular engineering of porphyrin
sensitizers, Nat. Chem., 2014, 6, 242.
Properties of Oxidized Single-Walled Carbon Nanotubes Helically 59 J. A. A. W. Elemans, R. van Hameren, R. J. M. Nolte and A. E.
Wrapped by Ionic, Semiconducting Polymers in Aqueous and
Organic Media, J. Am. Chem. Soc., 2014, 136, 14193–14199.
51 M. Cardona Claudia, W. Li, E. Kaifer Angel, D. Stockdale
Rowan, Molecular Materials by Self-Assembly of Porphyrins,
Phthalocyanines, and Perylenes, Adv. Mater., 2006, 18,
1251–1266.
and C. Bazan Guillermo, Electrochemical Considerations 60 S. Ogi, V. Stepanenko, J. Thein and F. Wu¨rthner, Impact of
for Determining Absolute Frontier Orbital Energy Levels of
Conjugated Polymers for Solar Cell Applications, Adv.
Mater., 2011, 23, 2367–2371.
Alkyl Spacer Length on Aggregation Pathways in Kinetically
Controlled Supramolecular Polymerization, J. Am. Chem.
Soc., 2016, 138, 670–678.
52 V. Lin, S. DiMagno and M. Therien, Highly conjugated, 61 Supramolecular Polymers, ed. A. Ciferri, Taylor & Francis,
acetylenyl bridged porphyrins: new models for light- Durham, NC, 2nd edn, 2005.
harvesting antenna systems, Science, 1994, 264, 1105–1111. 62 T. F. A. De Greef, M. M. J. Smulders, M. Wolffs, A. P. H. J.
53 P. Deria, J. Yu, R. P. Balaraman, J. Mashni and S. N. White,
Topology-dependent emissive properties of zirconium-based
porphyrin MOFs, Chem. Commun., 2016, 52, 13031–13034.
54 T. V. Duncan, T. Ishizuka and M. J. Therien, Molecular
Engineering of Intensely Near-Infrared Absorbing Excited
States in Highly Conjugated Oligo(porphinato)zinc–(Poly-
Schenning, R. P. Sijbesma and E. W. Meijer, Supramolecular
Polymerization, Chem. Rev., 2009, 109, 5687–5754.
63 X. Zhang, Z. Chen and F. Wu¨rthner, Morphology Control of
Fluorescent Nanoaggregates by Co-Self-Assembly of Wedge-
and Dumbbell-Shaped Amphiphilic Perylene Bisimides,
J. Am. Chem. Soc., 2007, 129, 4886–4887.
pyridyl)metal(II) Supermolecules, J. Am. Chem. Soc., 2007, 64 E. Kossoy, H. Weissman and B. Rybtchinski, Bending Nano-
129, 9691–9703.
55 J.-H. Olivier, Y. Bai, H. Uh, H. Yoo, M. J. Therien and
F. N. Castellano, Near-Infrared-to-Visible Photon Upconversion
fibers into Nanospirals: Coordination Chemistry as a Tool
for Shaping Hydrophobic Assemblies, Chem. – Eur. J., 2014,
21, 166–176.
Enabled by Conjugated Porphyrinic Sensitizers under Low- 65 K.-I. Goto, T.-H. Yu, J. Wu, C. H. Diaz and J. P. Colinge,
Power Noncoherent Illumination, J. Phys. Chem. A, 2015, 119,
5642–5649.
56 J. Rawson, A. C. Stuart, W. You and M. J. Therien, Tailoring
Mobility and screening effect in heavily doped accumulation-
mode metal-oxide-semiconductor field-effect transistors,
Appl. Phys. Lett., 2012, 101, 073503.
Porphyrin-Based Electron Accepting Materials for Organic 66 S. Wang, X. L. Liang, Q. Chen, Z. Y. Zhang and L. M. Peng,
Photovoltaics, J. Am. Chem. Soc., 2014, 136, 17561–17569.
57 J. Park, T.-H. Park, L. E. Sinks, P. Deria, J. Park, M.-H. Baik
and M. J. Therien, Unusual solvent polarity dependent
Field-Effect Characteristics and Screening in Double-Walled
Carbon Nanotube Field-Effect Transistors, J. Phys. Chem. B,
2005, 109, 17361–17365.
excitation relaxation dynamics of a bis[ p-ethynyldithiobenzoato]- 67 R. Martel, T. Schmidt, H. R. Shea, T. Hertel and P. Avouris,
Pd-linked bis[(porphinato)zinc] complex, Mol. Syst. Des. Eng.,
2018, 3, 275–284.
Single- and multi-wall carbon nanotube field-effect transistors,
Appl. Phys. Lett., 1998, 73, 2447–2449.
J. Mater. Chem. C
This journal is ©The Royal Society of Chemistry 2018