Linda Shimizu

We report herein the synthesis and metal complexation properties of two macrocyclic hosts that contain two 2,2'-bipyridines and two urea groups. These hosts take advantage of the conformationally mobile 5,5'-positions of the bipyridines to give metal binding sites that are dynamic. By simple bond rotation, these hosts can exchange an interior (endo) situated metal binding site for an exterior (exo) binding site. We examine the solid-state structures of the two free hosts and two coordination complexes ([Cd(host 1)(H(2)O)(NO(3))(2)] and [Ag(2)(host 2)](SO(3)CF(3))(2)) using X-ray crystallography. Analysis of these crystal structures suggests that the bipyridine groups within the hosts are able to rotate to access multiple conformations including the desired exo and endo conformations. We also investigate the binding affinity of these new ligands in solution by UV-vis titrations with…

A methylene urea bridged di-iodo triphenylamine dimer and its corresponding methylene di-iodo triphenylamine monomer are crystallized to correlate their structures with properties. In addition, their conductivity is compared against Spiro-OMeTAD.

Here, we compare structures determined by X-ray diffraction and subsequent Hirshfeld surface analysis to identify and understand the non-covalent interactions within the lattices of chromone, 6-methylchromone, 6-methoxychromone, 6-fluorochromone, and 6-chlorochromone with reported 6-bromochromone. In chromone, H-bonds and CH–л interactions predominate. H-bonds and aryl-stacking interactions are distinct in 6-methylchromone and 6-methoxychromone. The 6-fluorochromone, showed two types of H-bonds with O···H bonds having a greater contribution than F···H. In contrast, 6-chlorochromone and 6-bromochromone, the halogen contributes the larger percentage of stabilizing H-bonding with Cl···H and Br···H predominating over the O···H bonds. Compound 1 crystallizes in the monoclinic space group P21/n with a = 8.1546(8) Å, b = 7.8364(7) Å, c = 11.1424(11) Å, β = 108.506(2)° and Z = 4. Compound 2 crystallizes in the triclinic space group P-1 with a = 7.0461(3) Å, b = 10.2108(5) Å, c = 10.7083(5) Å, α = 89.884(2)°, β = 77.679(2)°, γ = 87.367(2)° and Z = 4. Compound 3 crystallizes in the monoclinic space group P21/n with a = 8.1923(4) Å, b = 7.0431(3) Å, c = 15.3943(8) Å, β = 92.819(2)° and Z = 4. Compound 4 crystallizes in the triclinic space group P1 with a = 3.7059(2) Å, b = 6.1265(4) Å, c = 7.6161(5) Å, α = 84.085(3)°, β = 87.070(3)°, γ = 83.390(3)° and Z = 1. Compound 5 crystallizes in the monoclinic space group P21 with a = 3.8220(2) Å, b = 5.6985(2) Å, c = 16.9107(7) Å, β = 95.8256(18)° and Z = 2.Graphical AbstractThe effect of substituents at the 6-position on chromone on their crystal structures using Hirshfeld surface and fingerprint analysis.

Abstract Herein, we investigate co-crystallization of three linear co-formers that contain urea and pyridyl groups with three regioisomers of diiodotetrafluorobenzene (DITFB) to afford eleven co-crystals. The linear o-, m-, and p- dipyridylureas vary distance and geometry between the urea carbonyl oxygen and two pyridyl nitrogen acceptors, while the donors consist of urea NH groups and the activated halides in DITFB. Electrostatic potential calculations suggest that the o-dipyridylurea co-former presents two significantly different acceptors. In comparison, the acceptors in the m- and p-dipyridylurea co-formers display electrostatic potentials within 5–6 kJ/mol and should be competitive, potentially leading to altered assembly motifs. Overall, ten of the co-crystals consistently display the urea assembly motif as the best acceptor/donor pair. Seven structures were obtained as the predicted 1:1 ratio with halogen bonding interactions linking ditopic halogen bond donors and the pyridyl units through N···I interactions ranging from 78.4 to 83.1% of the van der Waals radii. Modified structures were more likely when there was a structural mismatch with the geometrically challenging o-DITFB donor and m- or p-dipyridylurea co-former. The majority of the co-crystal structures (10/11) demonstrated fully satisfied hydrogen and halogen bonding interactions suggesting that these synthons can be used synergistically to generate complex solid-state structures.

... Mark D. Smith, † Youyong Li, ‡ and Linda S. Shimizu* †. Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, Materials and Process Simulation Center, California Institute of Technology, California 91125. J. Am. Chem. ...

We report a highly selective 2 + 2 cycloaddition of 2-cyclohexenone in the presence of self-assembled bisurea macrocycles that yields the head-to-tail photodimer. The reaction proceeds with high conversion and with decreased incidence of secondary photorearrangement. Furthermore, the product can be extracted from the assembly, and the solid assembly is readily recovered and reused, much like a zeolite.

ABSTRACT Single Crystal to Single Crystal Polymerization of a Self-Assembled Diacetylene Macrocycle Affords Columnar Polydiacetylenes PDF [1578 KB]PDF w/ Links[742 KB]Abstract Add to ACS ChemWorx Weiwei L. Xu , Mark D Smith , Jeanette A Krause , Andrew B. Greytak , Shuguo Ma , Cory M. Read , and Linda S. Shimizu Cryst. Growth Des., 2014, 14, 993-1002 DOI: 10.1021/cg401380a Publication Date (Web): January 23, 2014 Copyright © 2014 American Chemical Society CASSection:Chemistry of Synthetic High Polymers Abstract This manuscript describes a single-crystal-to-single-crystal polymerization of the dihydrate of diacetylene 1 (1•2H2O) to give an unusual polydiacetylene (PDA) structure that consists of aligned nanotubes, with each covalently-bonded nanotube having two parallel PDA chains that run parallel down opposite sides of a channel defined by the macrocycle. Each PDA nanotube is connected with four other columns via amide hydrogen bonds with an N-(H)---O distance of 2.888(4) Å. Such well-ordered polymers should display quasi-one-dimensional electronic structures and may be of interest for the formation of highly conductive organic materials. We obtained the 1•2H2O form in bulk, which was polymerized by heating. Powder X-ray diffraction suggests that bulk PDA powder is single phase and displays a similar structure as the PDA single crystals. Furthermore, we showed that PDA crystals absorbed I2 vapor. We believe that this unique PDA structure, which is amenable to property control via adsorbed guests, will be an attractive one for investigating charge-transfer doping in PDA-based organic electronic materials. We also observed two additional crystal forms including 1•MeOH, which also shows columnar assembly, and a tetrahydrate 1•4H2O that shows water tetramers that link four cycles into a 2D sheet structure.

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Gas-phase ion-mobility spectrometry provides a unique platform to study the effect of mobile charge(s) or charge location on collisional cross section and ion separation. Here, we evaluate the effects of cation/anion adduction in a series of xylene and pyridyl macrocycles that contain ureas and thioureas. We explore how zinc binding led to unexpected deprotonation of the thiourea macrocyclic host in positive polarity ionization and subsequently how charge isomerism due to cation (zinc metal) and anion (chloride counterion) adduction or proton competition among acceptors can affect the measured collisional cross sections in helium and nitrogen buffer gases. Our approach uses synthetic chemistry to design macrocycle targets and a combination of ion-mobility spectrometry mass spectrometry experiments and quantum mechanics calculations to characterize their structural properties. We demonstrate that charge isomerism significantly improves ion-mobility resolution and allows for determination of the metal binding mechanism in metal-inclusion macrocyclic complexes. Additionally, charge isomers can be populated in molecules where individual protons are shared between acceptors. In these cases, interactions via drift gas collisions magnify the conformational differences. Finally, for the macrocyclic systems we report here, charge isomers are observed in both helium and nitrogen drift gases with similar resolution. The separation factor does not simply increase with increasing drift gas polarizability. Our study sheds light on important properties of charge isomerism and offers strategies to take advantage of this phenomenon in analytical separations.

Pharmacological inhibition of LY6K induced cell cycle arrest and DNA damage by disrupting the LY6K-Histone-Aurora B signaling axis Benson C. Selvanesan1,2, Sheelu Varghese1,2, Justyna Andrys5, Ricardo H. Arriaza6, Rahul Prakash6, Purushottam B Tiwari7, Cara Olsen8, Daniel Hupalo2,4, Yuriy Gusev5, Megha N. Patel6, Sara Contente1, Miloslav Sanda9, Aykut Uren7, Matthew D. Wilkerson3,4, Clifton L. Dalgard3,4, Linda S. Shimizu6, Maksymilian Chruszcz6, Tomasz Borowski5, Geeta Upadhyay 1,3,7. Affiliations 1 Department of Pathology, 2 Henry M. Jackson Foundation, 3 Murtha Cancer Center, 4 Department of Anatomy, Physiology, and Genetics 8 Department of Preventive Medicine and Biostatistics Uniformed Services University of the Health Sciences, Bethesda, MD, USA. 5 Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Cracow, Poland. 6 Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA. 7 Department of Oncology, Georgetown U...

An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Herein we probe the effects of crystalline structure and geometry on benzophenone photophysics, self-quenching, and the regenerable formation of persistent triplet radical pairs at room temperature. Radical pairs are not observed in solution but appear via an emergent pathway within the solid-state assembly. Single crystal X-ray diffraction (SC-XRD) of two sets of constitutional isomers, benzophenone bis-urea macrocycles, and methylene urea-tethered dibenzophenones are compared. Upon irradiation with 365 nm light-emitting diodes (LEDs), each forms photogenerated radicals as monitored by electron paramagnetic resonance (EPR). Once generated, the radicals exhibit half-lives from 2 to 60 days before returning to starting material without degradation. Re-exposure to light regenerates the radicals with similar efficiency. Subtle differences in the structure of the crystalline frameworks modulates the maximum concentration of photogenerated radicals, phosphorescence quantum efficiency (φ), and n-type self-quenching as observed using laser flash photolysis (LFP). These studies along with the electronic structure analysis based on the time-dependent density functional theory (TD-DFT) suggest the microenvironment surrounding benzophenone largely dictates the favorability of self-quenching or radical formation and affords insights into structure/function correlations. Advances in understanding how structure determines the excited state pathway solid-state materials undertake will aid in the design of new radical initiators, components of OLEDs, and NMR polarizing agents.