Kathryn A. McGarry

Connecting Molecular Structure and Exciton Diffusion Length in Rubrene Derivatives

Connecting molecular structure and exciton diffusion length in rubrene derivatives demonstrates how the diffusion length of rubrene can be enhanced through targeted functionalization aiming to enhance self-Förster energy transfer. Functionalization adds steric bulk, forcing the molecules farther apart on average, and leading to increased photoluminescence efficiency. A diffusion length enhancement greater than 50% is realized over unsubstituted rubrene.

Utilizing carbon nanotube electrodes to improve charge injection and transport in bis(trifluoromethyl)-dimethyl-rubrene ambipolar single crystal transistors

We have examined the significant enhancement of ambipolar charge injection and transport properties of bottom-contact single crystal field-effect transistors (SC-FETs) based on a new rubrene derivative, bis(trifluoromethyl)-dimethyl-rubrene (fm-rubrene), by employing carbon nanotube (CNT) electrodes. The fundamental challenge associated with fm-rubrene crystals is their deep-lying HOMO and LUMO energy levels, resulting in inefficient hole injection and suboptimal electron injection from conventional Au electrodes due to large Schottky barriers. Applying thin layers of CNT network at the charge injection interface of fm-rubrene crystals substantially reduces the contact resistance for both holes and electrons; consequently, benchmark ambipolar mobilities have been achieved, reaching 4.8 cm(2) V(-1) s(-1) for hole transport and 4.2 cm(2) V(-1) s(-1) for electron transport. We find that such improved injection efficiency in fm-rubrene is beneficial for ultimately unveiling its intrinsic charge transport properties so as to exceed those of its parent molecule, rubrene, in the current device architecture. Our studies suggest that CNT electrodes may provide a universal approach to ameliorate the charge injection obstacles in organic electronic devices regardless of charge carrier type, likely due to the electric field enhancement along the nanotube located at the crystal/electrode interface.

Selective Formation of ortho-Aminobenzylamines by the Copper-Catalyzed Amination of Benzylamine Boronate Esters

The copper-catalyzed coupling between benzylamino boronate esters and aryl amines has been investigated. Formation of ortho-aminobenzylamines was achieved under oxidative conditions in the presence of copper(II) acetate. The major side product of the transformation is the homocoupling of the aryl boronate ester. The formation of the desired diamines was found to be improved in the absence of base, increasing selectivity over the homocoupled product. Both electron-donating and electron-withdrawing substituents are tolerated on both the boronate ester substrate and the aniline coupling partner under the reaction conditions. The presence of the adjacent benzylamine moiety appears to enhance the reactivity of the boronate ester and influence the resulting product distribution, likely by affecting the competing rates of transmetalation in the catalytic cycles.

Synthesis of Biaryl Ethers by the Copper-Catalyzed Chan–Evans–Lam Etherification from Benzylic Amine Boronate Esters

The copper-catalyzed etherification of ortho-borylated benzylic amines with phenols has been achieved to provide biaryl ethers that are prevalent in biologically active compounds. A variety of substitution patterns on the aryl boronate ester and the phenol are tolerated under the reaction conditions, providing moderate to high yields. A competition reaction between phenol and aniline revealed condition-dependent selectivity in which the phenol could be highly favored over the aniline.

Development and Mechanistic Study of Quinoline-Directed Acyl C-O Bond Activation and Alkene Oxyacylation Reactions

The intramolecular addition of both an alkoxy and acyl substituent across an alkene, oxyacylation of alkenes, using rhodium catalyzed C-O bond activation of an 8-quinolinyl ester is described. Our unsuccessful attempts at intramolecular carboacylation of ketones via C-C bond activation ultimately informed our choice to pursue and develop the intramolecular oxyacylation of alkenes via quinoline-directed C-O bond activation. We provide a full account of our catalyst discovery, substrate scope, and mechanistic experiments for quinoline-directed alkene oxyacylation.

Preparation of 6,11-Dihydroxy-5,12-tetracenedione

Our syntheses of tetracene derivatives necessitated access to inexpensive, analytically pure, multi-gram quantities of 3. A previous procedure for the preparation of 3 was reported by Sartori in 1987.9 In our hands, Sartori’s procedure was unwieldy at a larger scale because of difficult extractions and column chromatography. Moreover, we could only obtain 3 in significantly diminished yield and purity at the larger scale, compared to the original report. Older approaches for the synthesis of 3 involve rearrangements and condensations that proceed in low yields and also involve difficult purifications.10,11 Although 3 is commercially available, its high cost (Aldrich lists 1g for

Rubrene-Based Single-Crystal Organic Semiconductors: Synthesis, Electronic Structure, and Charge-Transport Properties

63.20 at 96% purity, May 2010) makes it a significant financial barrier in academic research. Our procedure makes substantial modifications to Sartori’s procedure, affording analytically pure 3 on a multi-gram scale using only washing and precipitation techniques. If one synthesizes 1,4-naphthalenediol (1), over 10 grams of 3 are produced using reagents and solvents costing a total of

Intrinsic non-radiative voltage losses in fullerene-based organic solar cells

57 (May 2010). Although 1 is also commercially available,