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1. X-ray crystal structure of trans -bis(pyridin-3-yl)ethylene: comparing the supramolecular structural features among the symmetrical bis( n -pyridyl)ethylenes ( n = 2, 3, or 4) constitutional isomers

   https://doi.org/10.1107/S2056989020015303  

   Quentin, Jay; Reinheimer, Eric W.; MacGillivray, Leonard R. (December 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   The molecular structure of trans -bis(pyridin-3-yl)ethylene ( 3,3′-bpe ), C 12 H 10 N 2 , as determined by single-crystal X-ray diffraction is reported. The molecule self-assembles into two dimensional arrays by a combination of C—H...N hydrogen bonds and edge-to-face C—H... π interactions that stack in a herringbone arrangement perpendicular to the crystallographic c -axis. The supramolecular forces that direct the packing of 3,3′-bpe as well as its packing assembly within the crystal are also compared to those observed within the structures of the other symmetrical isomers trans -1,2-bis( n -pyridyl)ethylene ( n , n ′-bpe , where n = n ′ = 2 or 4). 

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2. Synthesis and crystal structure of catena -poly[[tetra-μ-acetato-copper(II)]-μ-6-ethoxy- N ² , N ⁴ -bis[2-(pyridin-2-yl)ethyl]-1,3,5-triazine-2,4-diamine]

   https://doi.org/10.1107/S2056989021002164  

   Ayodele, Mayokun J.; Green, Travis C.; Warsapperuma, W. A.; Forbes, Malcolm D.; Ostrowski, Alexis D. (March 2021, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   The title compound, [Cu 2 (C 19 H 23 N 7 O)(C 2 H 3 O 2 ) 4 ] n , was obtained via reaction of copper(II) acetate with the coordinating ligand, 6-ethoxy- N 2 , N 4 -bis[2-(pyridin-2-yl)ethyl]-1,3,5-triazine-2,4-diamine. The crystallized product adopts the monoclinic P 2 1 / c space group. The metal core exhibits a paddle-wheel structure typical for dicopper tetraacetate units, with triazine and pyridyl nitrogen atoms from different ligands coordinating to the two axial positions of the paddle wheel in an asymmetric manner. This forms a coordination polymer with the segments of the polymer created by the c -glide of the P 2 1 / c setting of the space group. The resulting chains running along the c -axis direction are held together by intramolecular N—H...O hydrogen bonding. These chains are further packed by dispersion forces, producing an extended three-dimensional structure. 

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3. Crystal structure and photoreactivity of a halogen-bonded cocrystal based upon 1,2-diiodoperchlorobenzene and 1,2-bis(pyridin-4-yl)ethylene

   https://doi.org/10.1107/S2053229620006233  

   Bosch, Eric; Battle, Jessica D.; Groeneman, Ryan H. (June 2020, Acta Crystallographica Section C Structural Chemistry)

   null (Ed.)

   The formation of a photoreactive cocrystal based upon 1,2-diiodoperchlorobenzene ( 1,2-C 6 I 2 Cl 4 ) and trans -1,2-bis(pyridin-4-yl)ethylene ( BPE ) has been achieved. The resulting cocrystal, 2( 1,2-C 6 I 2 Cl 4 )·( BPE ) or C 6 Cl 4 I 2 ·0.5C 12 H 10 N 2 , comprises planar sheets of the components held together by the combination of I...N halogen bonds and halogen–halogen contacts. Notably, the 1,2-C 6 I 2 Cl 4 molecules π-stack in a homogeneous and face-to-face orientation that results in an infinite column of the halogen-bond donor. As a consequence of this stacking arrangement and I...N halogen bonds, molecules of BPE also stack in this type of pattern. In particular, neighbouring ethylene groups in BPE are found to be parallel and within the accepted distance for a photoreaction. Upon exposure to ultraviolet light, the cocrystal undergoes a solid-state [2 + 2] cycloaddition reaction that produces rctt -tetrakis(pyridin-4-yl)cyclobutane ( TPCB ) with an overall yield of 89%. A solvent-free approach utilizing dry vortex grinding of the components also resulted in a photoreactive material with a similar yield. 

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4. Engineering bistetrazoles: ( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol) as a new planar high-energy-density material

   https://doi.org/10.1039/d2ma00664b  

   Singh, Jatinder; Staples, Richard J.; Shreeve, Jean'ne M. (July 2022, Materials Advances)

   Energetic properties of bistetrazole derivatives are improved by the step-by-step introduction of functionalities which improve heat of formation, density, and oxygen content. The incorporation of unsaturation between bis(1 H -tetrazol-5-yl) and bis(1 H -tetrazol-1-ol) derivatives leads to planarity which enhances the density of the final product. In this manuscript, we have synthesized compounds 1,2-di(1 H -tetrazol-5-yl)ethane (4), ( E )-1,2-di(1 H -tetrazol-5-yl)ethene (5), and ( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol), (6) using readily available starting materials. Their corresponding dihydroxylammonium salts 7, 8 and 9 are obtained by reacting two equivalents of hydroxylamine (50% in water). New compounds are analyzed using IR, EA, DSC and multinuclear NMR spectroscopy ( 1 H, 13 C and 15 N). The solid-state structures of compounds 6, 7, 8 and 9 are confirmed by single-crystal X-ray diffraction. The energetic performances are calculated using the EXPLO5 (v6.06.02) code and the sensitivities towards external stimuli such as friction and impact are determined according to BAM standard. Compound 6 {( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol)} exhibits a surprisingly high density of 1.91 g cm −3 at 100 K (1.86 g cm −3 at 298 K). Its detonation velocity (9017 m s −1 ) is considerably superior to those of RDX (8795 m s −1 ), which suggests it is a competitive high-energy-density material. 

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5. Effect of the aromatic substituent on the para -position of pyridine-bis(oxazoline) sensitizers on the emission efficiency of their Eu ^III and Tb ^III complexes

   https://doi.org/10.1039/d0dt03135f  

   de Bettencourt-Dias, Ana; Rossini, Jeffrey S.; Sobrinho, Josiane A. (December 2020, Dalton Transactions)

   null (Ed.)

   Two efficient lanthanide ion sensitizers 2,6-bis(oxazoline)-4-phenyl-pyridine (PyboxPh, 1 ) and 2,6-bis(oxazoline)-4-thiophen-2-yl-pyridine (Pybox2Th, 2 ) were synthesized. 1 crystallizes in the monoclinic space group P 21/ c with cell parameters a = 16.3794(4) Å, b = 7.2856(2) Å, c = 11.7073(3) Å, β = 97.229(1)° and V = 1385.97(6) Å 3 . 2 crystallizes in the monoclinic space group P 21/ n with cell parameters a = 5.9472(2), b = 16.0747(6), c = 14.3716(5) Å, β = 93.503(1)° and V = 1371.35(8) Å 3 . Photophysical characterization of 1 shows that its triplet state energy is located at 22 250 cm −1 and efficient energy transfer is observed for Eu III and Tb III . Solutions of [Ln(PyboxPh) 3 ] 3+ in dichloromethane display an emission efficiency of 37.2% for LnEu and 24.0% for LnTb. The excited state lifetimes for Eu III and Tb III are 2.227 ms and 723 μs, respectively. The triplet state energy of 2 is located at 19 280 cm −1 and is therefore too low to efficiently sensitize Tb III emission. However, the sensitization of Eu III is effective, with an emission quantum yield of 14.5% and an excited state lifetime of 714 μs. This shows that the derivatization of the chelator is strongly influenced by the aromatic substituents on the para -position of the pyridine ring. New isostructural 1 : 1 complexes of PyboxPh with Eu III ( 3 ) and Tb III ( 4 ) were also isolated and crystallize in the triclinic space group P 1̄ with cell parameters a = 9.1845(2) Å, b = 10.3327(2) Å, c = 11.9654(2) Å, α = 98.419(1)°, β = 108.109(1)°, γ = 91.791(1)°, V = 1064.08(4) Å 3 and a = 7.8052(1) Å, b = 11.8910(1) Å, c = 14.2668(2) Å, α = 72.557(1)°, β = 86.355(1)°, γ = 77.223(1)°, V = 1231.95(3) Å 3 , respectively. 

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