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May 2017
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24 Reads
The Inside Cover picture highlights perturbations to vibrational energy levels and ¹³C NMR spectra of the acceptor pyrimidine upon complexation with halogen bond donors. Shifts and interaction energies increase with stronger electron withdrawing groups and more polarizable halogen atoms. More information can be found in the Full Paper by D. L. Watkins, G. S. Tschumper, N. I. Hammer, and co-workers on page 1267 in Issue 10, 2017 (DOI: 10.1002/cphc.201700114).
February 2017
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391 Reads
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21 Citations
The effects of intermolecular interactions by a series of haloaromatic halogen bond donors on the normal modes and chemical shifts of the acceptor pyrimidine are investigated by Raman and NMR spectroscopies and electronic structure computations. Halogen bond interactions with pyrimidine's nitrogen atoms shift normal modes to higher energy and shift 1H and 13C NMR peaks upfield in adjacent nuclei. This perturbation of vibrational normal modes is reminiscent of the effects of hydrogen bonded networks of water, methanol, or silver on pyrimidine. The unexpected observation of vibrational red shifts and downfield 13C NMR shifts in some complexes suggests that other intermolecular forces such as pi-interactions are competing with halogen bonding. Natural bond orbital analyses indicate a wide range of charge transfer from pyrimidine to different haloaromatic donors is possible and computed halogen bond binding energies can be larger than a typical hydrogen bond. These results emphasize the importance in strategic selection of substituents and electron withdrawing groups in developing supramolecular structures based on halogen bonding.
September 2015
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54 Reads
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15 Citations
Although recognized as a significant force in crystal engineering, halogen bonding (XB) has been scarcely investigated in "bottom-up" approaches towards organic electronics. We report, herein, the use of a thiophene-based building block, pyridyl-thiophene (Pyr-T), to achieve an assembly driven by XB and π-π stacking interactions with iodopentafluorobenzene (IPFB). Spectroscopic and thermal analysis of the co-crystal provide indirect evidence of the assembly. The combined effects of XB and π-π stacking are confirmed experimentally via X-ray crystallography. Density functional theory (DFT) computations support experimental observations. The results of the study speak to the use of halogen bond driven self-assembly in organic electronic device application. This journal is
... However, examination of this question has been fragmentary, with little in the way of general trends emerging from past work. A large fraction of the past work concentrated on the effects of the XB upon the electron donor unit [39][40][41][42], meaning it ignored issues arising within the acid. A few cases have been identified where XB formation leads to a red shift in the internal stretching frequency within the halogen donor, usually in small molecules such as a dihalogen [43,44], FX [45,46], CH 3 X [47], or CF 3 X [48], and there are cases where a blue shift has been observed [49], but little systematic work has addressed this issue in larger systems. ...
February 2017
... [12][13][14] More significantly, the framework constructions of aromatic linkers and metallic nodes can show strong affinity with thiophene-based aromatic sulfurs through the π-π and metal-π interactions. [15][16][17] Specifically, the open metal site in its secondary building unit (SBU) has shown promising adsorption selectivity of thiophene-based sulfurs over aromatics in fuel. 18 However, the existence of water in the crude oil during the extraction process can usually cause competitive adsorption, resulting in significant decreases in desulfurization efficiency. ...
September 2015
