A charge transfer framework that describes supramolecular interactions governing structure and properties of 2D perovskites.

The elucidation of structure-to-function relationships for two-dimensional (2D) hybrid perovskites remains a primary challenge for engineering efficient perovskite-based devices. By combining insights from theory and experiment, we describe the introduction of bifunctional ligands that are capable of making strong hydrogen bonds within the organic bilayer. We find that stronger intermolecular interactions draw charge away from the perovskite layers, and we have formulated a simple and intuitive computational descriptor, the charge separation descriptor (CSD), that accurately describes the relationship between the Pb-I-Pb angle, band gap, and in-plane charge transport with the strength of these interactions. A higher CSD value correlates to less distortion of the Pb-I-Pb angle, a reduced band gap, and higher in-plane mobility of the perovskite. These improved material properties result in improved device characteristics of the resulting solar cells.

Supramolecular Assemblies for Electronic Materials.

This work presents a synergy between organic electronics and supramolecular chemistry, in which a host-guest complex is designed to function as an efficacious electronic material. Specifically, the noncovalent recognition of a fullerene, phenyl-C61 -butyric acid methyl ester (PC61 BM), by an alternating perylene diimide (P)-bithiophene (B) conjugated macrocycle (PBPB) results in a greater than five-fold enhancement in electron mobility, relative to the macrocycle alone. Characterization and quantification of the binding of fullerenes by host PBPB is provided alongside evidence for intermolecular electronic communication within the host-guest complexes.

Conjugated Macrocycles in Organic Electronics.

This Account describes a body of research on the design, synthesis, and application of a new class of electronic materials made from conjugated macrocycles. Our macrocyclic design takes into consideration the useful attributes of fullerenes and what properties make fullerenes efficient n-type materials. We identified four electronic and structural elements: (1) a three-dimensional shape; (2) a conjugated and delocalized π-space; (3) the presence of an interior and exterior to the π-surface; and (4) low-energy unoccupied molecular orbitals allowing them to accept electrons. The macrocyclic design incorporates some of these properties, including a three-dimensional shape, an interior/exterior to the π-surface, and low-lying LUMOs maintaining the n-type semiconducting behavior, yet we also install synthetic flexibility in our approach in order to tune the properties further. Each of the macrocycles comprises perylenediimide cores wound together with linkers. The perylenediimide building block endows each macrocycle with the ability to accept electrons, while the synthetic flexibility to install different linkers allows us to create macrocycles with different electronic properties and sizes. We have created three macrocycles that all absorb well into the visible range of the solar spectrum and possess different shapes and sizes. We then use these materials in an array of applications that take advantage of their ability to function as n-type semiconductors, absorb in the visible range of the solar spectrum, and possess intramolecular cavities. This Account will discuss our progress in incorporating these new macrocycles in organic solar cells, organic photodetectors, organic field effect transistors, and sensors. The macrocycles outperform acyclic controls in organic solar cells. We find the more rigid macrocyclic structure results in less intrinsic charges and lower dark current in organic photodetectors. Our macrocyclic-based photodetector has the highest detectivity of non-fullerene acceptors. The macrocycles also function as sensors and are able to recognize nuanced differences in analytes. Perylenediimide-based fused oligomers are efficient materials in both organic solar cells and field effect transistors. We will use the oligomers to construct macrocycles for use in solar energy conversion. In addition, we will incorporate different electron-rich linkers in our cycles in an attempt to engineer the HOMO/LUMO gap further. Looking further into the future, we envision opportunities in applying these conjugated macrocycles as electronic host/guest materials, as concatenated electronic materials by threading the macrocycles with electroactive oligomers, and as a locus for catalysis that is driven by light and electric fields.

The importance of intramolecular conductivity in three dimensional molecular solids.

Recent years have seen tremendous progress towards understanding the relation between the molecular structure and function of organic field effect transistors. The metrics for organic field effect transistors, which are characterized by mobility and the on/off ratio, are known to be enhanced when the intermolecular interaction is strong and the intramolecular reorganization energy is low. While these requirements are adequate when describing organic field effect transistors with simple and planar aromatic molecular components, they are insufficient for complex building blocks, which have the potential to localize a carrier on the molecule. Here, we show that intramolecular conductivity can play a role in controlling device characteristics of organic field effect transistors made with macrocycle building blocks. We use two isomeric macrocyclic semiconductors that consist of perylene diimides linked with bithiophenes and find that the trans-linked macrocycle has a higher mobility than the cis-based device. Through a combination of single molecule junction conductance measurements of the components of the macrocycles, control experiments with acyclic counterparts to the macrocycles, and analyses of each of the materials using spectroscopy, electrochemistry, and density functional theory, we attribute the difference in electron mobility of the OFETs created with the two isomers to the difference in intramolecular conductivity of the two macrocycles.

Influence of Molecular Conformation on Electron Transport in Giant, Conjugated Macrocycles.

We describe here the direct connection between the molecular conformation of a conjugated macrocycle and its macroscopic charge transport properties. We incorporate chiral, helical perylene diimide ribbons into the two separate macrocycles as the n-type, electron transporting material. As the macrocycles' films and electronic structures are analogous, the important finding is that the macrocycles' molecular structures and their associated dynamics determine device performance in organic field effect transistors. We show the more flexible macrocycle has a 4-fold increase in electron mobility in field effect transistor devices. Using a combination of spectroscopy and density functional theory calculations, we find that the origin of the difference in device performance is the ability of more flexible isomer to make intermolecular contacts relative to the more rigid counterpart.

Hollow organic capsules assemble into cellular semiconductors.

Self-assembly of electroactive molecules is a promising route to new types of functional semiconductors. Here we report a capsule-shaped molecule that assembles itself into a cellular semiconducting material. The interior space of the capsule with a volume of ~415 Å3 is a nanoenvironment that can accommodate a guest. To self-assemble these capsules into electronic materials, we functionalize the thiophene rings with bromines, which encode self-assembly into two-dimensional layers held together through halogen bonding interactions. In the solid state and in films, these two-dimensional layers assemble into the three-dimensional crystalline structure. This hollow material is able to form the active layer in field effect transistor devices. We find that the current of these devices has strong response to the guest's interaction within the hollow spaces in the film. These devices are remarkable in their ability to distinguish, through their electrical response, between small differences in the guest.

Rigid, Conjugated Macrocycles for High Performance Organic Photodetectors.

Organic photodetectors (OPDs) are attractive for their high optical absorption coefficient, broad wavelength tunability, and compatibility with lightweight and flexible devices. Here we describe a new molecular design that enables high performance organic photodetectors. We use a rigid, conjugated macrocycle as the electron acceptor in devices to obtain high photocurrent and low dark current. We make a direct comparison between the devices made with the macrocyclic acceptor and an acyclic control molecule; we find that the superior performance of the macrocycle originates from its rigid, conjugated, and cyclic structure. The macrocycle's rigid structure reduces the number of charged defects originating from deformed sp2 carbons and covalent defects from photo/thermoactivation. With this molecular design, we are able to suppress dark current density while retaining high responsivity in an ultrasensitive nonfullerene OPD. Importantly, we achieve a detectivity of ∼1014 Jones at near zero bias voltage. This is without the need for extra carrier blocking layers commonly employed in fullerene-based devices. Our devices are comparable to the best fullerene-based photodetectors, and the sensitivity at low working voltages (<0.1 V) is a record for nonfullerene OPDs.

Macrocyclization in the Design of Organic n-Type Electronic Materials.

Here, we compare analogous cyclic and acyclic π-conjugated molecules as n-type electronic materials and find that the cyclic molecules have numerous benefits in organic photovoltaics. This is the first report of such a direct comparison. We designed two conjugated cycles for this study. Each comprises four subunits: one combines four electron-accepting, redox-active, diphenyl-perylenediimide subunits, and the other alternates two electron-donating bithiophene units with two diphenyl-perylenediimide units. We compare the macrocycles to acyclic versions of these molecules and find that, relative to the acyclic analogs, the conjugated macrocycles have bathochromically shifted UV-vis absorbances and are more easily reduced. In blended films, macrocycle-based devices show higher electron mobility and good morphology. All of these factors contribute to the more than doubling of the power conversion efficiency observed in organic photovoltaic devices with these macrocycles as the n-type, electron transporting material. This study highlights the importance of geometric design in creating new molecular semiconductors. The ease with which we can design and tune the electronic properties of these cyclic structures charts a clear path to creating a new family of cyclic, conjugated molecules as electron transporting materials in optoelectronic and electronic devices.

Chiral Conjugated Corrals.

We present here a new design motif for strained, conjugated macrocycles that incorporates two different aromatics into the cycle with an -A-B-A-B- pattern. In this study, we demonstrate the concept by alternating electron donors and acceptors in a conjugated cycle. The donor is a bithiophene, and the acceptor is a perylene diimide derivative. The macrocycle formed has a persistent elliptiform cavity that is lined with the sulfur atoms of the thiophenes and the π-faces of the perylene diimide. Due to the linkage of the perylene diimide subunits, the macrocycles exist in both chiral and achiral forms. We separate the three stereoisomers using chiral high-performance liquid chromatography and study their interconversion. The mechanism for interconversion involves an "intramolecular somersault" in which one of the PDIs rotates around its transverse axis, thereby moving one of its diimide heads through the plane of the cavity. These unusual macrocycles are black in color with an absorption spectrum that spans the visible range. Density functional theory calculations reveal a photoinduced electron transfer from the bithiophene to the perylene diimide.

Contorted polycyclic aromatics.

CONSPECTUS: This Account describes a body of research in the design, synthesis, and assembly of molecular materials made from strained polycyclic aromatic molecules. The strain in the molecular subunits severely distorts the aromatic molecules away from planarity. We coined the term "contorted aromatics" to describe this class of molecules. Using these molecules, we demonstrate that the curved pi-surfaces are useful as subunits to make self-assembled electronic materials. We have created and continue to study two broad classes of these "contorted aromatics": discs and ribbons. The figure that accompanies this conspectus displays the three-dimensional surfaces of a selection of these "contorted aromatics". The disc-shaped contorted molecules have well-defined conformations that create concave pi-surfaces. When these disc-shaped molecules are substituted with hydrocarbon side chains, they self-assemble into columnar superstructures. Depending on the hydrocarbon substitution, they form either liquid crystalline films or macroscopic cables. In both cases, the columnar structures are photoconductive and form p-type, hole- transporting materials in field effect transistor devices. This columnar motif is robust, allowing us to form monolayers of these columns attached to the surface of dielectrics such as silicon oxide. We use ultrathin point contacts made from individual single-walled carbon nanotubes that are separated by a few nanometers to probe the electronic properties of short stacks of a few contorted discs. We find that these materials have high mobility and can sense electron-deficient aromatic molecules. The concave surfaces of these disc-shaped contorted molecules form ideal receptors for the molecular recognition and assembly with spherical molecules such as fullerenes. These interfaces resemble ball-and-socket joints, where the fullerene nests itself in the concave surface of the contorted disc. The tightness of the binding between the two partners can be increased by creating more hemispherically shaped contorted molecules. Given the electronic structure of these contorted discs and the fullerenes, this junction is a molecular version of a p-n junction. These ball-and-socket interfaces are ideal for photoinduced charge separation. Photovoltaic devices containing these molecular recognition elements demonstrate approximately two orders of magnitude increase in charge separation. The ribbon-shaped, contorted molecules can be conceptualized as ultranarrow pieces of graphene. The contortion causes them to wind into helical ribbons. These ribbons can be formed into the active layer of field effect transistors. We substitute the ribbons with di-imides and therefore are able to transport electrons. Furthermore, these materials absorb light strongly and have ideal energetic alignment of their orbitals with conventional p-type electronic polymers. In solar cells, these contorted ribbons with commercial donor polymers have record efficiencies for non-fullerene-based solar cells. An area of interest for future exploration is the merger of these highly efficient contorted ribbons with the well-defined interfaces of the ball-and-socket materials.

Metabolic effects associated with atypical antipsychotic treatment in the developmentally disabled.

OBJECTIVE: Atypical antipsychotics, especially clozapine and olanzapine, have been increasingly associated with weight gain and other adverse metabolic events (diabetes mellitus, hyperlipidemia) in non-mentally retarded populations. This report explores the incidence of this phenomenon in an institution-dwelling population of individuals with developmental disabilities. METHOD: A retrospective longitudinal analysis was performed for a sample of 41 adults with developmental disabilities and comorbid psychiatric and/or behavioral syndromes for whom treatment was converted from typical antipsychotics to olanzapine or risperidone for a minimum period of 2 years. Data were collected from October 1998 to September 2002. Among parameters analyzed were chlorpromazine equivalent dosage of antipsychotic, metabolic parameters, body mass index (BMI), level of concurrent medications, and concomitant dietary restrictions. RESULTS: Thirty-two study subjects (78.0%) were men. The mean age of the study subjects was 43.6 years (at the end of the study). Thirty-seven (90.2%) had severe-to-profound mental retardation. Eight (19.5%) were on a restricted diet. Twenty-three subjects (56.1%) were switched from a typical antipsychotic to olanzapine, and 18 subjects (43.9%) were switched from a typical antipsychotic to risperidone. Of the subsample of subjects who were switched from a typical antipsychotic to risperidone, 12 (66.7%) went on to be switched to olanzapine because of either emergent side effects or lack of efficacy. For the overall sample (N = 41), there was a 19.3% increase in chlorpromazine-equivalent antipsychotic dosage from baseline to the 2-year endpoint along with a 5.6% decrease in fasting blood glucose from baseline to the 2-year endpoint. There were no significant differences between baseline and endpoint values for BMI, total cholesterol, low-density lipoprotein cholesterol, or triglycerides. CONCLUSION: The findings of this 2-year evaluation suggest that clinically or statistically significant BMI increases as well as blood glucose and lipid elevations are not unavoidably correlated with the use of the atypical antipsychotic agents olanzapine and risperi-done and may be minimized by careful monitoring, a regimen of dietary control, and a moderate activity level in a residential population of individuals with mental retardation.

Clozapine-induced hyperlipidemia resolved after switch to aripiprazole therapy.

OBJECTIVE: To report a case of severe clozapine-induced hypercholesterolemia and hypertriglyceridemia that resolved after therapy was switched to aripiprazole. CASE SUMMARY: A 42-year-old white man with schizoaffective disorder experienced new-onset hyperlipidemia with the addition of clozapine therapy. Despite treatment with various antihyperlipidemic agents, his total cholesterol level reached 477 mg/dL and his triglyceride level reached 4758 mg/dL. After a decrease in adherence with clozapine and subsequent deterioration, the patient was hospitalized and his antipsychotic therapy was switched to aripiprazole. The patient's lipid levels improved dramatically to the point that antihyperlipidemic treatment was discontinued. Due to lack of adequate symptomatic relief of psychiatric symptoms, the patient was ultimately switched back to clozapine therapy, at which time his lipid levels started to worsen again. DISCUSSION: There is a critical scarcity of data that relate to aripiprazole-induced lipid changes. Some studies have suggested that aripiprazole is not associated with the development of hyperlipidemia. Our case indicates that aripiprazole therapy may not have an adverse effect on lipid levels, even in patients who have a history of hyperlipidemia induced by another atypical antipsychotic. CONCLUSIONS: Should aripiprazole be found to have a definitive lipid-neutral effect, then clinicians would be wise to factor this finding into overall benefit-versus-risk considerations in the antipsychotic treatment selection process, especially in a society in which cardiovascular disease continues to be a principal cause of morbidity and mortality.

To bleed or not to bleed: young women's attitudes toward menstrual suppression.

The purpose of this study was to investigate women's knowledge about and attitudes toward the medical suppression of menstruation. One hundred and three female undergraduate students completed several questionnaires. Thirty-five percent of the participants were familiar with menstrual suppression, and 12% reported using birth control methods to suppress their menses; oral contraceptive users were more knowledgeable about menstrual suppression than other women. Women who regarded menstruation as bothersome and shameful were more supportive of suppression than women with more positive attitudes. Women who scored higher on measures of body consciousness were not more likely to support menstrual suppression or to report a desire for more information about menstrual suppression. Future investigations of women's attitudes toward menstrual suppression could inform reproductive health care and health education.