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1. Brightly phosphorescent tetranuclear copper( i ) pyrazolates

   https://doi.org/10.1039/c9dt03402a  

   Dias, H. V.; Diyabalanage, Himashinie V.; Ghimire, Mukunda M.; Hudson, Joshua M.; Parasar, Devaborniny; Palehepitiya Gamage, Chammi S.; Li, Shan; Omary, Mohammad A. (October 2019, Dalton Transactions)

   null (Ed.)

   Described herein is the synthesis and photophysics of two tetranuclear copper complexes, {[3,5-(Pr i ) 2 ,4-(Br)Pz]Cu} 4 and {[3-(CF 3 ),5-(Bu t )Pz]Cu} 4 tailor-designed by manipulating the pyrazolyl ring substituents. Unlike their trinuclear analogues, the luminescence of the tetranuclear species is molecular (not supramolecular) in nature with extremely high solid-state quantum yields of ∼80% at room temperature. 

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2. Tetranuclear and trinuclear copper( i ) pyrazolates as catalysts in copper mediated azide–alkyne cycloadditions (CuAAC)

   https://doi.org/10.1039/d1dt04026j  

   Patterson, Monika R.; Dias, H. V. (December 2021, Dalton Transactions)

   Homoleptic, tetranuclear copper( i ) pyrazolates {[3,5-( t -Bu) 2 Pz]Cu} 4 , {[3-(CF 3 )-5-( t -Bu)Pz]Cu} 4 , and {[4-Br-3,5-( i -Pr) 2 Pz]Cu} 4 are excellent stand-alone catalysts for azide–alkyne cycloaddition reactions (CuAAC). This work demonstrates that a range of pyrazolates, including those with electron donating and electron-withdrawing groups to sterically demanding substituents on the pyrazolyl backbones, can serve as effective ligand supports on tetranuclear copper catalysts. However, in contrast to the tetramers and also highly fluorinated {[3,5-(CF 3 ) 2 Pz]Cu} 3 , trinuclear copper( i ) complexes such as {[3,5-( i -Pr) 2 Pz]Cu} 3 and {[3-(CF 3 )-5-(CH 3 )Pz]Cu} 3 supported by relatively electron rich pyrazolates display poor catalytic activity in CuAAC. The behavior and degree of aggregation of several of these copper( i ) pyrazolates in solution were examined using vapor pressure osmometry. Copper( i ) complexes such as {[3,5-(CF 3 ) 2 Pz]Cu} 3 and {[3-(CF 3 )-5-( t -Bu)Pz]Cu} 4 with electron withdrawing pyrazolates were found to break up in solution to different degrees producing smaller aggregates while those such as {[3,5-( i -Pr) 2 Pz]Cu} 3 and {[3,5-( t -Bu) 2 Pz]Cu} 4 with electron rich pyrazolates remain intact. In addition, kinetic experiments were performed to understand the unusual activity of tetranuclear copper( i ) pyrazolate systems. 

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3. Cu( i )–O ₂ oxidation reactions in a fluorinated all-O-donor ligand environment

   https://doi.org/10.1039/C8DT05028G  

   Brazeau, Sarah E.; Doerrer, Linda H. (April 2019, Dalton Transactions)

   Investigation of Cu–O 2 oxidation reactivity is important in biological and anthropogenic chemistry. Zeolites are one of the most promising Cu/O based oxidation catalysts for development of industrial-scale CH 4 to CH 3 OH conversion. Their oxidation mechanisms are not well understood, however, highlighting the importance of the investigation of molecular Cu( i )–O 2 reactivity with O-donor complexes. Herein, we give an overview of the synthesis, structural properties, and O 2 reactivity of three different series of O-donor fluorinated Cu( i ) alkoxides: K[Cu(OR) 2 ], [(Ph 3 P)Cu(μ-OR) 2 Cu(PPh 3 )], and K[(R 3 P)Cu(pin F )], in which OR = fluorinated monodentate alkoxide ligands and pin F = perfluoropinacolate. This breadth allowed for the exploration of the influence of the denticity of the ligand, coordination number, the presence of phosphine, and K⋯F/O interactions on their O 2 reactivity. K⋯F/O interactions were required to activate O 2 in the monodentate-ligand-only family, whereas these connections did not affect O 2 activation in the bidentate complexes, potentially due to the presence of phosphine. Both families formed trisanionic, trinuclear cores of the form {Cu 3 (μ 3 -O) 2 } 3− . Intramolecular and intermolecular substrate oxidation were also explored and found to be influenced by the fluorinated ligand. Namely, {Cu 3 (μ 3 -O) 2 } 3− from K[Cu(OR) 2 ] could perform both monooxygenase reactivity and oxidase catalysis, whereas those from K[(R 3 P)Cu(pin F )] could only perform oxidase catalysis. 

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4. Structural diversity in copper(I) iodide complexes with 6-thioxopiperidin-2-one, piperidine-2,6-dithione and isoindoline-1,3-dithione ligands

   https://doi.org/10.1107/S2056989020009676  

   Wheaton, Amelia M.; Guzei, Ilia A.; Berry, John F. (August 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-dithione (SNS), isoindoline-1,3-dithione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis[(acetonitrile-κ N )(6-sulfanylidenepiperidin-2-one-κ S )copper(I)], [Cu 2 I 2 (CH 3 CN) 2 (C 5 H 7 NOS) 2 ] ( I ), bis(acetonitrile-κ N )tetra-μ 3 -iodido-bis(6-sulfanylidenepiperidin-2-one-κ S )- tetrahedro -tetracopper(I), [Cu 4 I 4 (CH 3 CN) 4 (C 5 H 7 NOS) 4 ] ( II ), catena -poly[[(μ-6-sulfanylidenepiperidin-2-one-κ 2 O : S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NOS)] n ( III ), poly[[(piperidine-2,6-dithione-κ S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NS 2 )] n ( IV ), and poly[[(μ-isoindoline-1,3-dithione-κ 2 S : S )copper(I)]-μ 3 -iodido], [CuI(C 8 H 5 NS 2 )] n ( V ). Compounds I and II crystallize as discrete dimeric and tetrameric complexes, whereas III , IV , and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexagonal [Cu 3 I 3 ] structure that is not supported by bridging ligands. Structures I , II , and IV display weak to moderately strong Cu...Cu cuprophilic interactions [Cu...Cu internuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding interactions between the N—H of the ligand and the μ 2 and μ 3 -I − atoms. Structure III contains classical N–H...O interactions between the SNO ligands that connect the molecules in a three-dimensional framework. Complex V features π–π stacking interactions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV , there were three partially occupied solvent molecules of dichloromethane and one partially occupied molecule of acetonitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015). Acta Cryst . C 71 , 9–18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent molecules. The given chemical formula and other crystal data do not take into account the solvent molecules. 

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5. Nickel( ii ) complexes based on dithiolate–polyamine binary ligand systems: crystal structures, hirshfeld surface analysis, theoretical study, and catalytic activity study on photocatalytic hydrogen generation

   https://doi.org/10.1039/d1dt00352f  

   Adhikari, Suman; Bhattacharjee, Tirtha; Bhattacharjee, Sharmila; Daniliuc, Constantin Gabriel; Frontera, Antonio; Lopato, Eric M.; Bernhard, Stefan (April 2021, Dalton Transactions)

   null (Ed.)

   To ascertain the influence of binary ligand systems [1,1-dicyanoethylene-2,2-dithiolate (i-mnt −2 ) and polyamine {tetraen = tris(2-aminoethyl)amine, tren = diethylene triamine and opda = o -phenylenediamine}] on the coordination modes of the Ni( ii ) metal center and resulting supramolecular architectures, a series of nickel( ii ) thiolate complexes [Ni(tetraen)(i-mnt)](DMSO) ( 1 ), [Ni 2 (tren) 2 (i-mnt) 2 ] ( 2 ), and [Ni 2 (i-mnt) 2 (opda) 2 ] n ( 3 ) have been synthesized in high yield in one step in water and structurally characterized by single crystal X-ray crystallography and spectroscopic techniques. X-ray diffraction studies disclose the diverse i-mnt −2 coordination to the Ni +2 center in the presence of active polyamine ligands, forming a slightly distorted octahedral geometry (NiN 4 S 2 ) in 1 , square planar (NiS 4 ) and distorted octahedral geometries (NiN 6 ) in the bimetallic co-crystallized aggregate of cationic [Ni(tren) 2 ] +2 and anionic [Ni(i-mnt) 2 ] −2 in 2 , and a one dimensional (1D) polymeric chain along the [100] axis in 3 , having consecutive square planar (NiS 4 ) and octahedral (NiN 6 ) coordination kernels. The N–H⋯O, N–H⋯S, N–H⋯N, N–H⋯S, N–H⋯N, and N–H⋯O type hydrogen bonds stabilize the supramolecular assemblies in 1 , 2 , and 3 respectively imparting interesting graph-set-motifs. The molecular Hirshfeld surface analyses (HS) and 2D fingerprint plots were utilized for decoding all types of non-covalent contacts in the crystal networks. Atomic HS analysis of the Ni +2 centers reveals significant Ni–N metal–ligand interactions compared to Ni–S interactions. We have also studied the unorthodox interactions observed in the solid state structures of 1–3 by QTAIM and NBO analyses. Moreover, all the complexes proved to be highly active water reduction co-catalysts (WRC) in a photo-catalytic hydrogen evolution process involving iridium photosensitizers, wherein 2 and 3 having a square planar arrangement around the nickel center(s) – were found to be the most active ones, achieving 1000 and 1119 turnover numbers (TON), respectively. 

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