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331 results on '"Parkin, Sean R."'

1. Antiferro- and Meta-magnetism in the S=7/2 Hollandite Analog EuGa2Sb2

Author

Berry, Tanya, Parkin, Sean R., and McQueen, Tyrel M.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

Recent work analyzing the impact of non-symmorphic symmetries on electronic states has given rise to the discovery of multiple types of topological matter. Here we report the single-crystal synthesis and magnetic properties of EuGa2Sb2, an Eu-based antiferromagnet structurally consisting of pseudo-1D chains of Eu ions related by a non-symmorphic glide plane. We find the onset of antiferromagnetic order at TN = 8 K. Above TN the magnetic susceptibility is isotropic. Curie-Weiss analysis suggests competing ferromagnetic and antiferromagnetic interactions, with peff = 8.1 muB as expected for 4f7 J = S = 7/2 Eu^2+ ions. Below TN and at low applied magnetic fields, an anisotropy develops linearly, reaching chi perpendicular over chi parallel =6 at T = 2 K. There is concomitant metamagnetic behavior along with chi parallel, with a magnetic field of mu0 H=0.5 T sufficient to suppress the anisotropy. Independent of crystal orientation, there is a continuous evolution to a field polarized paramagnetic state with M=7 muB/Eu^2+ cation at mu0 H=2 T as T approaches 0 K. Specific heat measurements show a recovered magnetic entropy of dSmag=16.4 J/mol.K from T near 0 K to T = TN, close to the expected value of Rln(8) for an S = 7/2 ion, indicating negligible low dimensional spin fluctuations above TN. We find no evidence of unusual behaviors arising either from the dimensionality or the presence of the non-symmorphic symmetries.

Published
2021
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2. Supramolecular characterisation of salts of 4-(2-methoxyphenyl)piperazin-1-ium and 4-phenylpiperazin-1-ium cations with simple-organic anions; a closer look at the binding energies of cation-anion pairs formed by charge-assisted (+)N−H···O(-) and (+)N−H···O hydrogen bonds

Author

Prasad, Holehundi J. Shankara, Kumar, Haleyur G. Anil, Kumar, Thaluru M. Mohan, Kavitha, Channappa N., Devaraju, Yathirajan, Hemmige S., Parkin, Sean R., and Chęcińska, Lilianna

Published
2023
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13. Hydrogen-Bonded Chain of Rings Motif in N -(4-Methoxyphenyl)piperazin-1-ium Salts with Benzoate Anions: Supramolecular Assemblies and Their Energy Frameworks.

Author

Priyanka, Prabhakar, Jayanna, Bidarur K., Divakara, Thayamma R., Suresha, Gejjalagere P., Vinaya, Basavaraju, Yeriyur B., Yathirajan, Hemmige S., Parkin, Sean R., and Chęcińska, Lilianna

Subjects
IONIC interactions, BENZOATES, HYDROGEN bonding, CRYSTAL structure, ANIONS, SALTS
Abstract

The crystal structures of three salts, namely N-(4-methoxyphenyl)piperazin-1-ium ethoxybenzoate monohydrate (I), N-(4-methoxyphenyl)piperazin-1-ium methoxybenzoate monohydrate (II) and N-(4-methoxyphenyl)piperazin-1-ium hydroxybenzoate monohydrate (III), have been determined and compared. In each of them, the ionic components and the water molecules are linked by a combination of N—H···O and O—H···O hydrogen bonds to form infinite chains of edge-fused centrosymmetric rings running parallel to the [100] direction. The C—H···O, C—H···π(arene) interactions and O—H···O in (III) are responsible for the further propagation of the aforementioned chains into di-periodic layers or tri-periodic networks. From an energetic point of view, all structures are primarily di-periodic; the very strong ionic interactions determine the periodicity. For comparison purposes, quantum chemical calculations were performed to show the difference between the ionic and neutral components. The energy of the hydrogen-bonded ring motifs was also estimated. [ABSTRACT FROM AUTHOR]

Published
2022
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16. Computationally aided design of a high-performance organic semiconductor: the development of a universal crystal engineering core† †Electronic supplementary information (ESI) available: Synthetic details, characterization of synthesized materials, absorption spectra, and additional information on computational details and device fabrication. CCDC 1833615–1833619 and 1922871–1922873. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c9sc02930c

Author

Petty, Anthony J., Ai, Qianxiang, Sorli, Jeni C., Haneef, Hamna F., Purdum, Geoffrey E., Boehm, Alex, Granger, Devin B., Gu, Kaichen, Rubinger, Carla Patricia Lacerda, Parkin, Sean R., Graham, Kenneth R., Jurchescu, Oana D., Loo, Yueh-Lin, Risko, Chad, and Anthony, John E.

Subjects
Chemistry
Abstract

Silylethyne-functionalized benzodithiophene serves as a universal crystal engineering core to yield stable, soluble, π-stacked arrays of aromatic chromophores., Herein, we describe the design and synthesis of a suite of molecules based on a benzodithiophene “universal crystal engineering core”. After computationally screening derivatives, a trialkylsilylethyne-based crystal engineering strategy was employed to tailor the crystal packing for use as the active material in an organic field-effect transistor. Electronic structure calculations were undertaken to reveal derivatives that exhibit exceptional potential for high-efficiency hole transport. The promising theoretical properties are reflected in the preliminary device results, with the computationally optimized material showing simple solution processing, enhanced stability, and a maximum hole mobility of 1.6 cm2 V–1 s–1.

Published
2019

21. Syntheses and crystal structures of 4-(4-nitrophenyl) piperazin-1-ium benzoate monohydrate and 4-(4-nitrophenyl)piperazin-1-ium 2-carboxy-4,6-dinitrophenolate.

Author

Prasad, Holehundi J. Shankara, Devaraju, Vinaya, Yathirajan, Hemmige S., Parkin, Sean R., and Glidewell, Christopher

Subjects
CRYSTAL structure, PIPERAZINE, BENZOATES, BENZOIC acid, HYDROGEN bonding, ETHYL acetate, CRYSTALLIZATION
Abstract

Crystal structures are reported for two mol­ecular salts containing the 4-(4-nitro­phen­yl)piperazin-1-ium cation. Co-crystallization from methanol/ethyl acetate solution of N-(4-nitro­phen­yl)piperazine with benzoic acid gives the benzoate salt, which crystallizes as a monohydrate, C10H14N3O2·C7H5O2·H2O, (I), and similar co-crystallization with 3,5-di­nitro­salicylic acid yields the 2-carb­oxy-4,6-di­nitro­phenolate salt, C10H14N3O2·C7H3N2O7, (II). In the structure of (I), a combination of O--H...O, N--H...O and C--H...O hydrogen bonds links the components into sheets, while in the structure of (II), the supra­molecular assembly, generated by hydrogen bonds of the same types as in (I), is three dimensional. Comparisons are made with the structures of some related compounds. [ABSTRACT FROM AUTHOR]

Published
2022
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24. Probing the Effects of Electron Deficient Aryl Substituents and a π‐System Extended NHC Ring on the Photocatalytic CO 2 Reduction Reaction with Re‐pyNHC‐Aryl Complexes**

Author

Shirley, Hunter, primary, Sexton, Thomas More, additional, Liyanage, Nalaka P., additional, Perkins, Morgan A., additional, Autry, Shane A., additional, McNamara, Louis E., additional, Hammer, Nathan I., additional, Parkin, Sean R., additional, Tschumper, Gregory S., additional, and Delcamp, Jared H., additional

Published
2021
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34. Pictet–Spengler condensations using 4-(2-aminoethyl)coumarins

Author

Sviripa, Vitaliy M., primary, Fiandalo, Michael V., additional, Begley, Kristin L., additional, Wyrebek, Przemyslaw, additional, Kril, Liliia M., additional, Balia, Andrii G., additional, Parkin, Sean R., additional, Subramanian, Vivekanandan, additional, Chen, Xi, additional, Williams, Alexander H., additional, Zhan, Chang-Guo, additional, Liu, Chunming, additional, Mohler, James L., additional, and Watt, David S., additional

Published
2020
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38. Novel square arrangements in tetranuclear and octanuclear iron(III) complexes with asymmetric iron environments created by the unsymmetric bridging ligand N,N,N'-tris((N-methyl)-2-benzimidazolylmethyl)-N'-methyl-1,3-diamino-2-propa nol

Author

Satcher, Joe H., Jr., Olmstead, Marilyn M., Droege, Michael W., Parkin, Sean R., Noll, Bruce C., May, Leopold, and Balch, Alan L.

Subjects
Iron compounds -- Research, Coordination compounds -- Research, Inorganic compounds -- Synthesis, Ligands (Biochemistry) -- Research, Ions -- Research, Chemistry
Abstract

The synthesis and structural characterization of novel tetranuclear and octanuclear iron(III) complexes were described. The structures of the iron(III) complexes are based on an almost square arrangement of four iron ions. The tetranuclear iron complex (Fe4(mu-O)2(mu-BMDP)2-(mu-OAc)2)(super 4+) is formed by reacting ferric nitrate, sodium acetate and the unsymmetrical binucleating ligand HBMDP. The tetranuclear iron complex was found to have coordination number asymmetry.

Published
1998

40. Probing the Effects of Electron Deficient Aryl Substituents and a π‐System Extended NHC Ring on the Photocatalytic CO2 Reduction Reaction with Re‐pyNHC‐Aryl Complexes.

Author

Shirley, Hunter, Sexton, Thomas More, Liyanage, Nalaka P., Perkins, Morgan A., Autry, Shane A., McNamara, Louis E., Hammer, Nathan I., Parkin, Sean R., Tschumper, Gregory S., and Delcamp, Jared H.

Subjects
PHOTOREDUCTION, ELECTRONIC probes, ARYL group, PHOTOCATALYSIS, SYNTHETIC fuels, PHOTOCATALYSTS, RHENIUM
Abstract

The ever‐expanding need for renewable energy can be addressed in part by photocatalytic CO2 reduction to give fuels via an artificial photosynthetic process driven by sunlight. A series of rhenium photocatalysts are evaluated in the photocatalytic CO2 reduction reaction and via photophysical, electrochemical, and computational studies. The impact of various electron withdrawing substituents on the aryl group of the pyNHC‐aryl ligand along with the impact of extending conjugation along the backbone of the ligand is analyzed. A strong correlation between excited‐state lifetimes, photocatalytic rates, and computationally determined dissociation energy of the labile ligand of these complexes is observed. Additionally, computed orbital analysis provides an added understanding, which allows for prediction of the potential impact of an electron withdrawing substituent on photocatalysis. [ABSTRACT FROM AUTHOR]

Published
2021
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49. Hydrogen Bonding Optimizes Singlet Fission in Carboxylic Acid Functionalized Anthradithiophene Films.

Author

Gish, Melissa K., Thorley, Karl J., Parkin, Sean R., Anthony, John E., and Johnson, Justin C.

Subjects
HYDROGEN bonding, CARBOXYLIC acids, MOLECULAR orientation, THIN films, PHOTOEXCITATION, PHOSPHORESCENCE spectroscopy, MAGNITUDE (Mathematics)
Abstract

The rate of singlet fission, the process of generating two triplet excitons with photoexcitation of one singlet exciton, depends on a combination of singlet/triplet energy balance and intermolecular coupling. Here, we perform carboxylic acid functionalization of anthradithiophene (ADT) derivatives that results in hydrogen bonds that drive molecular orientation and strong electronic coupling of polycrystalline ADT thin films, leading to ultrafast singlet fission without significant enthalpic driving force. ADT with a single carboxylic acid group exhibits weak intermolecular coupling and slow and inefficient singlet fission, much like the parent ADT, and substitution of different alkylsilyl solubilizing groups has little effect. However, the addition of two carboxylic acid groups on either end of the long axis favors significant coupling and crystallinity in as‐deposited thin films that increase the effective singlet fission rate by roughly three orders of magnitude. The properties of the triplet pair, particularly its propensity to form long‐lived independent triplets, are also influenced by the degree of long‐range intermolecular coupling. The enhancement of intermolecular coupling specific to singlet fission using the ubiquitous cyclic hydrogen bonding motif could impact triplet pair utilization schemes in a variety of contexts. [ABSTRACT FROM AUTHOR]

Published
2021
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50. Effect of Halogenation on the Energetics of Pure and Mixed Phases in Model Organic Semiconductors Composed of Anthradithiophene Derivatives and C60

Author

Abtahi, Ashkan, Mazza, Samuel M., Ryno, Sean M., Loya, E. Kirkbride, Li, Ruipeng, Parkin, Sean R., Risko, Chad, Anthony, John E., and Graham, Kenneth R.

Abstract

Halogenation, particularly fluorination, is commonly used to manipulate the energetics, stability, and morphology of organic semiconductors. In the case of organic photovoltaics (OPVs), fluorination of electron donor molecules or polymers at appropriate positions can lead to improved performance. In this contribution, we use ultraviolet photoelectron spectroscopy, external quantum efficiency measurements of charge-transfer (CT) states, and density functional theory calculations to systematically investigate the effects of halogenation on the bulk solid-state energetics of model anthradithiophene (ADT) materials, their interfacial energetics with C60, and the energetics of various ADT:C60blend compositions. In agreement with previous work, nonhalogenated ADT molecules show higher energy CT states in blends with C60and lower energy CT states in the ADT/C60bilayers. However, this trend is reversed in the halogenated ADT/C60systems, wherein the CT state energies of ADT:C60blends are lower than those in the bilayers. In bulk-heterojunction photovoltaics, the lower energy CT states present in the mixed phase with the halogenated ADT derivatives will likely decrease the probability of charge separation and increase charge recombination. The less favorable energy landscapes observed upon halogenation suggest that the benefits of fluorination observed in many OPV material systems may be more due to morphological factors.

Published
2024
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