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The unique properties of fluorinated organic compounds have received intense interest and have conquered a myriad of applications in the chemical and pharmaceutical sciences. Today, an impressive range of alkyl fluorides are commercially available, and there are many practical methods to make them exist. However, the unmatched stability and inertness of the C-F bond have largely limited its synthetic value, which is very different from the widely accepted utility of alkyl chlorides, bromides, and iodides that serve everyday as "workhorse" building blocks in countless carbon-carbon bond forming reactions. This study demonstrates practical and high-yielding functionalization of the C-F bond under mild conditions, i.e., at temperatures as low as -78 °C, in short reaction times and with unconventional chemoselectivity. Cryogenic Csp 3 -F bond cleavage using fluorophilic organoaluminum compounds together with fast nucleophile transfer of intermediate ate complexes forge carbon-carbon bonds with unactivated primary, secondary, and tertiary alkyl fluorides alike. This method, which exploits the stability of the Al-F bond as the thermodynamic driving force, is highly selective toward Csp 3 -F bond functionalization, whereas many other functional groups including alkyl chloride, bromide, iodide, aryl halide, alkenyl, alkynyl, difluoroalkyl, trifluoromethyl, ether, ester, hydroxyl, acetal, heteroaryl, nitrile, nitro, and amide groups are tolerated, which is an unexpected reversal of long-standing main group organometallic and alkyl halide cross-coupling reactivity and compatibility patterns. As a result, the strongest single bond in organic chemistry can now be selectively targeted in high-yielding arylation, alkylation, alkenylation, and alkynylation reactions and used in late-stage functionalization applications that are complementary to currently available methods.

Insights into the molecular mechanism and factors affecting nitrite-to-NO transformation at transition metal sites are essential for developing sustainable technologies relevant to NO-based therapeutics, waste water treatment, and agriculture. A set of copper(II)-nitrite complexes 1-4 have been isolated employing tridentate pincer-type ligands ( qu L, py L, ClArO L - , PhO L - ) featuring systematically varied donors. Although the X-ray crystal structures of the copper(II)-nitrite cores in 1-4 are comparable, electrochemical studies on complexes 1-4 reveal that redox properties of these complexes differ due to the changes in the σ-donor abilities of the phenolate/N-heterocycle based donor sites. Reactivity of these nitrite complexes with oxygen-atom-transfer (OAT) reagent (e. g. triphenyl phosphine Ph 3 P) and H + /e - donor reagent (e. g. substituted phenols ArOH) show the reduction of nitrite to NO gas. Detailed kinetic investigations including kinetic isotope effect (KIE), Eyring analyses for determining the activation parameters unfold that reduction of nitrite at copper(II) by Ph 3 P or ArOH are influenced by the Cu II /Cu I redox potential. Finally, this study allows mechanism driven development of catalytic nitrite reduction by ArOH in the presence of 10 mol % copper complex (1)., (© 2024 Wiley-VCH GmbH.)

Four cerium compounds - (HPy) 2 [CeCl 6 ]·2(HPyCl) (Ce1-1), (HPy) 2 [CeCl 6 ] (Ce1-2), (HPy) m [Ce 38 O 56- x (OH) x Cl 50 (H 2 O) 12 ]· n H 2 O (Ce38), and (HPy) m [Ce 52 O 80- x (OH) x Cl 59 (H 2 O) 17 ]· n H 2 O (Ce52) - were crystallized from acidic aqueous solutions using pyridinium (HPy) counterions. The latter consists of two unique cerium oxide nanoclusters that are built from 52 metal ions and represents the largest chloride capped {Ce III/IV O} and/or {M IV O} (M = Ce, Th, U, Np, Pu) nanocluster that adopts the fluorite-type structure of MO 2 that has been reported.

Generation of S -nitrosothiol (RSNO) and nitric oxide (NO) mediated by zinc(ii) coordination motifs is of prime importance for understanding the role of zinc(ii)-based cofactors in redox-signalling pathways. This study uniquely employs a set of mononuclear [L 2 Zn II ] 2+ cores (where L = Me 4 PzPz/Me 2 PzPy/Me 2 PzQu) for introducing subtle alterations of the primary coordination sphere and investigates the role of ligand tuning in the transformation of NO 2 - in the presence of thiols. Single crystal X-ray diffraction (SCXRD) analyses on [L 2 Zn II -X](X) (where X = perchlorate/triflate) illustrate consistent changes in the bond distances, thereby showing variations of the metal-ligand interactions depending on the nature of the heterocyclic donor arms (pyrazole/pyridine/quinoline). Moreover, such tuning of the ligands affects the Lewis-acidity of the [L 2 Zn II ] 2+ cores as evaluated by 31 P NMR and SCXRD studies on the 1 : 1 acid-base adducts [L 2 Zn II (OPEt 3 )] 2+ . Crystallographic and 15 N NMR spectroscopic analyses on the nitrite complexes [L 2 Zn II (κ 2 -nitrite)](ClO 4 ) reveal that the chemical environments of the nitrite anions in these complexes are nearly identical, despite the dissimilarity in the Lewis-acidity of the [L 2 Zn II ] 2+ cores. Interestingly, RSNO and NO generation from the reactions of [L 2 Zn II (κ 2 -nitrite)](ClO 4 ) with 4- tert -butylbenzylthiol ( t BuBnSH) exhibits that the [(Me 2 PzQu) 2 Zn II ] 2+ core is the most efficient in promoting nitrite-thiol interactions due to the ease of available hemilabile coordination sites at the Lewis acidic [Zn II ]. Detailed UV-vis studies in tandem with computational investigation, for the first time, provide an unambiguous demonstration of the nitrous acid (HNO 2 ) intermediate generated through an intramolecular proton-transfer from thiol to nitrite at zinc(ii)., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Piano stool complexes have been studied over many years and found widespread applications in organic synthesis, catalysis, materials and drug development. We now report the first examples of quantitative chiroptical molecular recognition of chiral compounds through click-like η 6 -arene coordination with readily available half sandwich complexes. This conceptually new approach to chirality sensing is based on irreversible acetonitrile displacement of [Cp*Ru(CH 3 CN) 3 ]PF 6 by an aromatic target molecule, a process that is fast and complete within a few minutes at room temperature. The metal coordination coincides with characteristic circular dichroism inductions that can be easily correlated to the absolute configuration and enantiomeric ratio of the bound molecule. A relay assay that decouples the determination of the enantiomeric composition and of the total sample amount by a practical CD/UV measurement protocol was developed and successfully tested. The introduction of piano stool complexes to the chiroptical sensing realm is mechanistically unique and extends the scope of currently known methods with small-molecule probes that require the presence of amino, alcohol, carboxylate or other privileged functional groups for binding of the target compound. A broad application range including pharmaceutically relevant multifunctional molecules and the use in chromatography-free asymmetric reaction analysis are also demonstrated., (© 2024 Wiley-VCH GmbH.)

Cerium-oxo clusters have applications in fields ranging from catalysis to electronics and also hold the potential to inform on aspects of actinide chemistry. Toward this end, a cerium-acetylacetonate (acac 1- ) monomeric molecule, Ce(acac) 4 ( Ce-1 ), and two acac 1- -decorated cerium-oxo clusters, [Ce 10 O 8 (acac) 14 (CH 3 O) 6 (CH 3 OH) 2 ]·10.5MeOH ( Ce-10 ) and [Ce 12 O 12 (OH) 4 (acac) 16 (CH 3 COO) 2 ]·6(CH 3 CN) ( Ce-12 ), were prepared and structurally characterized. The Ce(acac) 4 monomer contains Ce IV . Crystallographic data and bond valence summation values for the Ce-10 and Ce-12 clusters are consistent with both clusters having a mixture of Ce III and Ce IV cations. Ce L 3 -edge X-ray absorption spectroscopy, performed on Ce-10 , showed contributions from both Ce III and Ce IV . The Ce-10 cluster is built from a hexameric cluster, with six Ce IV sites, that is capped by two dimeric Ce III units. By comparison, Ce-12 , which formed upon dissolution of Ce-10 in acetonitrile, consists of a central decamer built from edge sharing Ce IV hexameric units, and two monomeric Ce III sites that are bound on the outer corners of the inner Ce 10 core. Electrospray ionization mass spectrometry data for solutions prepared by dissolving Ce-10 in acetonitrile showed that the major ions could be attributed to Ce 10 clusters that differed primarily in the number of acac 1- , OH 1- , MeO 1- , and O 2- ligands. Small angle X-ray scattering measurements for Ce-10 dissolved in acetonitrile showed structural units slightly larger than either Ce 10 or Ce 12 in solution, likely due to aggregation. Taken together, these results suggest that the acetylacetonate supported clusters can support diverse solution-phase speciation in organic solutions that could lead to stabilization of higher order cerium containing clusters, such as cluster sizes that are greater than the Ce 10 and Ce 12 reported herein.

Fluorooxindoles undergo asymmetric Michael addition to para -quinone methides under phase-transfer conditions with 10 mol% of a readily available cinchona alkaloid ammonium catalyst. This reaction affords sterically encumbered, multifunctional fluorinated organic compounds displaying two adjacent chirality centers with high yields, ee 's and dr 's.

Rare examples of trinuclear [Ni-N 2 -M-N 2 -Ni] core (M = Ca, Mg) with linear bridged dinitrogen ligands are reported in this work. The reduction of [ i Pr 2 NN]Ni(μ-Br) 2 Li(thf) 2 (1) ( i Pr 2 NN = 2,4-bis-(2,6-diisopropylphenylimido)pentyl) with elemental Mg or Ca in THF under an atmosphere of dinitrogen yields the complex { i Pr 2 NNNi(μ-N 2 )} 2 M (thf) 4 (M = Mg, complex 2 and M = Ca, complex 3). The bridging end-on (μ-N 2 ) 2 M(thf) 4 moiety connects the two [ i Pr 2 NNNi] - nickelate fragments. A combination of X-ray crystallography, solution and solid-state spectroscopy have been applied to characterize complexes 2 and 3, and DFT studies have been used to help explain the bonding and electronic structure in these unique Ni-N 2 -Mg and Ni-N 2 -Ca complexes.

Fluorinated organic compounds are frequently used across the chemical and life sciences. Although a large, structurally diverse pool of alkyl fluorides is nowadays available, synthetic applications trail behind the widely accepted utility of other halides. We envisioned that C(sp 2 )-C(sp 3 ) cross-coupling reactions of alkyl fluorides with fluorophilic organozinc compounds should be possible through a heterolytic mechanism that involves short-lived ion pairs and uses the stability of the Zn-F bond as the thermodynamic driving force. This would be mechanistically different from previously reported radical reactions and overcome long-standing limitations of organometallic cross-coupling methodology, including competing β-hydride elimination, homodimerization and hydrodefluorination. Here, we show a practical C sp3 -F bond functionalization method that expands the currently restricted synthetic space of unactivated primary, secondary and tertiary C(sp 3 )-F bonds but also uses benzylic, propargylic and acyl fluorides. Many functional groups and sterically demanding substrates are tolerated, which allows practical carbon-carbon bond formation and late-stage functionalization., (© 2024. The Author(s).)

Reduction of nitrate is an essential, yet challenging chemical task required to manage this relatively inert oxoanion in the environment and biology. We show that thiols, ubiquitous reductants in biology, convert nitrate to nitric oxide at a Cu(II) center under mild conditions. The β-diketiminato complex [Cl 2 NN F6 ]Cu(κ 2 -O 2 NO) engages in O-atom transfer with various thiols (RSH) to form the corresponding copper(II) nitrite [Cu II ](κ 2 -O 2 N) and sulfenic acid (RSOH). The copper(II) nitrite further reacts with RSH to give S -nitrosothiols RSNO and [Cu II ] 2 (μ-OH) 2 en route to NO formation via [Cu II ]-SR intermediates. The gasotransmitter H 2 S also reduces nitrate at copper(II) to generate NO, providing a lens into NO 3 - /H 2 S crosstalk. The interaction of thiols with nitrate at copper(II) releases a cascade of N- and S-based signaling molecules in biology.

Molecular catalysts for ammonia oxidation to dinitrogen represent enabling components to utilize ammonia as a fuel and/or source of hydrogen. Ammonia oxidation requires not only the breaking of multiple strong N-H bonds but also controlled N-N bond formation. We report a novel β-diketiminato copper complex [ i Pr 2 NN F6 ]Cu I -NH 3 ([Cu I ]-NH 3 ( 2 )) as a robust electrocatalyst for NH 3 oxidation in acetonitrile under homogeneous conditions. Complex 2 operates at a moderate overpotential (η = 700 mV) with a TOF max = 940 h -1 as determined from CV data in 1.3 M NH 3 -MeCN solvent. Prolonged (>5 h) controlled potential electrolysis (CPE) reveals the stability and robustness of the catalyst under electrocatalytic conditions. Detailed mechanistic investigations indicate that electrochemical oxidation of [Cu I ]-NH 3 forms {[Cu II ]-NH 3 } + ( 4 ), which undergoes deprotonation by excess NH 3 to form reactive copper(II)-amide ([Cu II ]-NH 2 , 6 ) unstable toward N-N bond formation to give the dinuclear hydrazine complex [Cu I ] 2 (μ-N 2 H 4 ). Electrochemical studies reveal that the diammine complex [Cu I ](NH 3 ) 2 ( 7 ) forms at high ammonia concentration as part of the {[Cu II ](NH 3 ) 2 } + /[Cu I ](NH 3 ) 2 redox couple that is electrocatalytically inactive. DFT analysis reveals a much higher thermodynamic barrier for deprotonation of the four-coordinate {[Cu II ](NH 3 ) 2 } + ( 8 ) by NH 3 to give the copper(II) amide [Cu II ](NH 2 )(NH 3 ) ( 9 ) (Δ G = 31.7 kcal/mol) as compared to deprotonation of the three-coordinate {[Cu II ]-NH 3 } + by NH 3 to provide the reactive three-coordinate parent amide [Cu II ]-NH 2 (Δ G = 18.1 kcal/mol) susceptible to N-N coupling to form [Cu I ] 2 (μ-N 2 H 4 ) (Δ G = -11.8 kcal/mol).

Reduction of nitrite anions (NO 2 - ) to nitric oxide (NO), nitrous oxide (N 2 O) and ultimately dinitrogen (N 2 ) takes place in a variety of environments, including in the soil as part of the biogeochemical nitrogen cycle and in acidified nuclear waste. Nitrite reduction typically takes place within the coordination sphere of a redox-active transition metal. Here we show that Lewis acid coordination can substantially modify the reduction potential of this polyoxoanion to allow for its reduction under non-aqueous conditions (-0.74 V versus NHE). Detailed characterization confirms the formation of the borane-capped radical nitrite dianion (NO 2 2- ), which features a N(II) oxidation state. Protonation of the nitrite dianion results in the facile loss of nitric oxide (NO), whereas its reaction with NO results in disproportionation to nitrous oxide (N 2 O) and nitrite (NO 2 - ). This system connects three redox levels in the global nitrogen cycle and provides fundamental insights into the conversion of NO 2 - to NO., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

The luminescence properties of two divalent europium complexes of the type Eu[N(SPPh 2 ) 2 ] 2 (THF) 2 ( 1 ) and Eu[N(SePPh 2 ) 2 ] 2 (THF) 2 ( 2 ) were investigated. The first complex, Eu[N(SPPh 2 ) 2 ] 2 (THF) 2 ( 1 ), was found to be isomorphous with the reported structure of complex 2 and exhibited room temperature luminescence with thermochromic emission upon cooling. We found the complex Eu[N(SePPh 2 ) 2 ] 2 (THF) 2 ( 2 ) was also thermochromic but the emission intensity was sensitive to temperature. Both room temperature and low temperature (100 K) single crystal X-ray structural investigation of 1 and 2 indicate geometric distortions of the metal coordination, which may be important for understanding the thermochromic behavior of these complexes. The trivalent europium complex Eu[N(SPPh 2 ) 2 ] 3 ( 3 ) with the same ligand as 1 was also structurally characterized as a function of temperature and exhibited temperature-dependent luminescence intensity, with no observable emission at room temperature but intense luminescence at 77 K. Variable temperature Raman spectroscopy was used to determine the onset temperature of luminescence of Eu[N(SPPh 2 ) 2 ] 3 ( 3 ), where the 615 nm ( 5 D 0 → 7 F 2 transition) peak was quenched above 130 K. The UV-visible diffuse reflectance of 3 provides evidence of an LMCT band, supporting a mechanism of thermally activated LMCT quenching of Eu(III) emitting states. A series of ten isomorphous, trivalent lanthanide complexes of type Ln[N(SPPh 2 ) 2 ] 3 (Ln = Eu ( 3 ) Pr ( 4 ), Nd ( 5 ), Sm ( 6 ), Gd ( 7 ), Tb ( 8 )) and Ln[N(SePPh 2 ) 2 ] 3 (Ln = Pr ( 9 ), Nd ( 10 , structure was previously reported), Sm ( 11 ), and Gd ( 12 ) for Q = Se) were also synthesized and structurally characterized. These complexes for Ln = Pr, Nd, Sm, and Tb exhibited room temperature luminescence. This study provides examples of temperature-dependent luminescence of both Eu 2+ and Eu 3+ , and the use of soft-atom donor ligands to sensitize lanthanide luminescence in a range of trivalent lanthanides, spanning near IR and visible emitters.

Copper nitrite reductases (CuNIRs) convert NO 2 - to NO as well as NO to N 2 O under high NO flux at a mononuclear type 2 Cu center. While model complexes illustrate N-N coupling from NO that results in symmetric trans -hyponitrite [Cu II ]-ONNO-[Cu II ] complexes, we report NO assembly at a single Cu site in the presence of an external reductant Cp* 2 M (M = Co, Fe) to give the first copper cis -hyponitrites [Cp* 2 M]{[Cu II ](κ 2 -O 2 N 2 )[Cu I ]}. Importantly, the κ 1 -N-bound [Cu I ] fragment may be easily removed by the addition of mild Lewis bases such as CNAr or pyridine to form the spectroscopically similar anion {[Cu II ](κ 2 -O 2 N 2 )} - . The addition of electrophiles such as H + to these anionic copper(II) cis -hyponitrites leads to N 2 O generation with the formation of the dicopper(II)-bis-μ-hydroxide [Cu II ] 2 (μ-OH) 2 . One-electron oxidation of the {[Cu II ](κ 2 -O 2 N 2 )} - core turns on H-atom transfer reactivity, enabling the oxidation of 9,10-dihydroanthracene to anthracene with concomitant formation of N 2 O and [Cu II ] 2 (μ-OH) 2 . These studies illustrate both the reductive coupling of NO at a single copper center and a way to harness the strong oxidizing power of nitric oxide via the neutral cis- hyponitrite [Cu](κ 2 -O 2 N 2 ).

The one-electron reduction of nitrite (NO 2 - ) to nitric oxide (NO) and ene-diol oxidation are two important biochemical transformations. Employing mononuclear cobalt-nitrite complexes with Co III and Co II oxidation states, [( Bz 3 Tren )Co III (nitrite) 2 ](ClO 4 ) ( 1 ) and [( Bz 3 Tren )Co II (nitrite)](ClO 4 ) ( 2 ), this report illustrates NO release coupled to stepwise oxidation of ene-diol antioxidants such as l-ascorbic acid (AH 2 ) and catechol. Analysis of the AH 2 end-product reveals that the reaction with complex 1 affords dehydroascorbic acid. Intriguingly, a controlled oxidation of AH 2 with complex 2 results in a [Co II ]-bound ascorbyl radical-anion ( 8 ). Finally, NO release with the concomitant generation of metal-bound 3,5-di- tert -butyl-semiquinone radical anion from the reactions of 3,5-di- tert -butyl-catechol and [( Bz 3 Tren )M II (nitrite)](ClO 4 ) ( 2 , M = Co; 4 , M = Zn) provides mechanistic insights into the cross-talk between nitrite and ene-diols at the metal sites.

A cerium-oxo nanocluster capped by chloride ligands, [Ce IV 38- n Ce III n O 56-( n +1) (OH) n +1 Cl 51 (H 2 O) 11 ] 10- ( n = 1-24), has been isolated from acidic chloride solutions by using potassium counterions. The crystal structure was elucidated using single crystal X-ray diffraction. At the center of the cluster is a {Ce 14 } core that exhibits the same fluorite-type structure as bulk CeO 2 , with eight-coordinate Ce sites bridged by tetrahedral oxo anions. The {Ce 14 } is further surrounded by a peripheral shell of six tetranuclear {Ce 4 } subunits that are located on each of the faces of the core to yield the {Ce 38 } cluster. The surface of the cluster is capped by 51 bridging/terminal chloride ligands and 11 water molecules; the anionic cluster is charge balanced by potassium counterions that exist in the outer coordination sphere. While assignment of the Ce oxidation state by bond valence summation was ambiguous, Ce L 3 -edge X-ray absorption, X-ray photoelectron, and UV-vis-NIR absorption results were consistent with a Ce III /Ce IV cluster. Systematic changes in the XANES and UV-vis-NIR absorption spectra over time pointed to reactivity of the cluster upon exposure to air. These changes were examined using single crystal X-ray diffraction, and a clear single-crystal-to-single-crystal transformation was captured; an overall loss of surface-bound chlorides and water molecules as well as new μ 2 -OH sites was observed on the cluster surface. This work provides a rare snapshot of metal oxide cluster reactivity. The results may hold implications for understanding the physical and chemical properties of ceria nanoparticles and provide insight into the behavior of other metal-oxo clusters of significant technological and environmental interest.

Commercially available benzophenone imine (HN[double bond, length as m-dash]CPh 2 ) reacts with β-diketiminato copper(ii) tert -butoxide complexes [Cu II ]-O t Bu to form isolable copper(ii) ketimides [Cu II ]-N[double bond, length as m-dash]CPh 2 . Structural characterization of the three coordinate copper(ii) ketimide [Me 3 NN]Cu-N[double bond, length as m-dash]CPh 2 reveals a short Cu-N ketimide distance (1.700(2) Å) with a nearly linear Cu-N-C linkage (178.9(2)°). Copper(ii) ketimides [Cu II ]-N[double bond, length as m-dash]CPh 2 readily capture alkyl radicals R˙ (PhCH(˙)Me and Cy˙) to form the corresponding R-N[double bond, length as m-dash]CPh 2 products in a process that competes with N-N coupling of copper(ii) ketimides [Cu II ]-N[double bond, length as m-dash]CPh 2 to form the azine Ph 2 C[double bond, length as m-dash]N-N[double bond, length as m-dash]CPh 2 . Copper(ii) ketimides [Cu II ]-N[double bond, length as m-dash]CAr 2 serve as intermediates in catalytic sp 3 C-H amination of substrates R-H with ketimines HN[double bond, length as m-dash]CAr 2 and t BuOO t Bu as oxidant to form N -alkyl ketimines R-N[double bond, length as m-dash]CAr 2 . This protocol enables the use of unactivated sp 3 C-H bonds to give R-N[double bond, length as m-dash]CAr 2 products easily converted to primary amines R-NH 2 via simple acidic deprotection., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A new bismuth(III)-organic compound, Hphen[Bi 2 (HPDC) 2 (PDC) 2 (NO 3 )]·4H 2 O ( Bi-1 ; PDC = 2,6-pyridinedicarboxylate and phen = 1,10-phenanthroline), was synthesized, and the structure was determined by single-crystal X-ray diffraction. The compound was found to display bright-blue-green phosphorescence in the solid state under UV irradiation, with a luminescent lifetime of 1.776 ms at room temperature. The room temperature and low-temperature (77 K) emission spectra exhibited the vibronic structure characteristic of Hphen phosphorescence. Time-dependent density functional theory studies showed that the excitation pathway arises from an energy transfer from the dimeric structural unit to Hphen, with participation from a nine-coordinate Bi center. The triplet state of Hphen is believed to be stabilized via supramolecular interactions, which, when coupled with the heavy-atom effect induced by Bi, leads to the observed long-lived luminescence. The compound displayed a solid-state quantum yield of over 27%. To the best of our knowledge, this is the first such compound to exhibit phenanthrolinium phosphorescence with such long-lived, room temperature lifetimes in the solid state. To further elucidate the energy-transfer mechanism, Ln 3+ (Ln = Eu, Tb, Sm) ions were successfully doped into the parent compound, and the resulting materials exhibited dual emission from Hphen and Ln, promoting tunability of the emission color.

Nitric oxide (NO) is a key signaling molecule in health and disease. While nitrite acts as a reservoir of NO activity, mechanisms for NO release require further understanding. A series of electronically varied β-diketiminatocopper(II) nitrite complexes [Cu II ](κ 2 -O 2 N) react with a range of electronically tuned triarylphosphines PAr Z 3 that release NO with the formation of O═PAr Z 3 . Second-order rate constants are largest for electron-poor copper(II) nitrite and electron-rich phosphine pairs. Computational analysis reveals a transition-state structure energetically matched with experimentally determined activation barriers. The production of NO follows a pathway that involves nitrite isomerization at Cu II from κ 2 -O 2 N to κ 1 -NO 2 followed by O-atom transfer (OAT) to form O═PAr Z 3 and [Cu I ]-NO that releases NO upon PAr Z 3 binding at Cu I to form [Cu I ]-PAr Z 3 . These findings illustrate important mechanistic considerations involved in NO formation from nitrite via OAT.

The life-sustaining reduction of N 2 to NH 3 is thermoneutral yet kinetically challenged by high-energy intermediates such as N 2 H 2 . Exploring intramolecular H-bonding as a potential strategy to stabilize diazene intermediates, we employ a series of [ x Het TpCu] 2 (μ-N 2 H 2 ) complexes that exhibit H-bonding between pendant aromatic N-heterocycles ( x Het) such as pyridine and a bridging trans -N 2 H 2 ligand at copper(I) centers. X-ray crystallography and IR spectroscopy clearly reveal H-bonding in [ pyMe TpCu] 2 (μ-N 2 H 2 ) while low-temperature 1 H NMR studies coupled with DFT analysis reveals a dynamic equilibrium between two closely related, symmetric H-bonded structural motifs. Importantly, the x Het pendant negligibly influences the electronic structure of x Het TpCu I centers in x Het TpCu(CNAr 2,6-Me 2 ) complexes that lack H-bonding as judged by nearly indistinguishable ν(CN) frequencies (2113-2117 cm -1 ). Nonetheless, H-bonding in the corresponding [ x Het TpCu] 2 (μ-N 2 H 2 ) complexes results in marked changes in ν(NN) (1398-1419 cm -1 ) revealed through resonance Raman studies. Due to the closely matched N-H BDEs of N 2 H 2 and the pyH 0 cation radical, the aromatic N-heterocyclic pendants may encourage partial H-atom transfer (HAT) from N 2 H 2 to x Het through redox-non-innocent H-bonding in [ x Het TpCu] 2 (μ-N 2 H 2 ). DFT studies reveal modest thermodynamic barriers for concerted transfer of both H-atoms of coordinated N 2 H 2 to the x Het pendants to generate tautomeric [ x HetH TpCu] 2 (μ-N 2 ) complexes, identifying metal-assisted concerted dual HAT as a thermodynamically favorable pathway for N 2 /N 2 H 2 interconversion.

NO and H 2 S serve as signaling molecules in biology with intertwined reactivity. HSNO and HSSNO with their conjugate bases - SNO and - SSNO form in the reaction of H 2 S with NO as well as S-nitrosothiols (RSNO) and nitrite (NO 2 - ) that serve as NO reservoirs. While HSNO and HSSNO are elusive, their conjugate bases form isolable zinc complexes Ph,Me TpZn(SNO) and Ph,Me TpZn(SSNO) supported by tris(pyrazolyl)borate ligands. Reaction of Na(15-C-5)SSNO with Ph,Me TpZn(ClO 4 ) provides Ph,Me TpZn(SSNO) that undergoes S-atom removal by PEt 3 to give Ph,Me TpZn(SNO) and S=PEt 3 . Unexpectedly stable at room temperature, these Zn-SNO and Zn-SSNO complexes release NO upon heating. Ph,Me TpZn(SNO) and Ph,Me TpZn(SSNO) quickly react with acidic thiols such as C 6 F 5 SH to form N 2 O and NO, respectively. Increasing the thiol basicity in p-substituted aromatic thiols 4-X ArSH in the reaction with Ph,Me TpZn(SNO) turns on competing S-nitrosation to form Ph,Me TpZn-SH and RSNO, the latter a known precursor for NO., (© 2021 Wiley-VCH GmbH.)

Seven novel bismuth(III)-halide phases, Bi 2 Cl 6 (terpy) 2 ·0.5(H 2 O) ( 1 ), Bi 2 Cl 4 (terpy) 2 ( k 2 -TC) 2 ( 2 ) (TC = 2-thiophene monocarboxylate), BiCl(terpy)( k 2 -TC) 2 ( 3A-Cl ), BiBr(terpy)( k 2 -TC) 2 ( 3A-Br ), BiCl(terpy)( k 2 -TC) 2 ( 3B-Cl ), [BiCl(terpy)( k 2 -TC) 2 ][Bi(terpy)( k 2 -TC) 3 ]·0.55(TCA) ( 4 ), [BiBr 3 (terpy)(MeOH)] ( 5 ), and [BiBr 2 (terpy)( k 2 -TC)][BiBr 1.16 (terpy)( k 2 -TC) 1.84 ] ( 6 ), were prepared under mild synthetic conditions from methanolic/aqueous solutions containing BiX 3 (X = Cl, Br) and 2,2':6',2″-terpyridine (terpy) and/or 2-thiophene monocarboxylic acid (TCA). A heterometallic series, 3A-Bi 1- x Eu x Cl , with the general formula Bi 1- x Eu x Cl(terpy)( k 2 -TC) 2 ( x = 0.001, 0.005, 0.01, 0.05) was also prepared through trace Eu doping of the 3A-Cl phase. The structures were determined through single-crystal X-ray diffraction and are built from a range of molecular units including monomeric and dimeric complexes. The solid-state photoluminescent properties of the compounds were examined through steady-state and time-resolved methods. While the homometallic phases exhibited broad green to yellow emission, the heterometallic phases displayed yellow, orange, and red emission that can be attributed to the simultaneous ligand/Bi-halide and Eu centered emissions. Photoluminescent color tuning was achieved by controlling the relative intensities of these concurrent emissions through compositional modifications including the Eu doping percentage. Notably, all emissive homo- and heterometallic phases exhibited rare visible excitation pathways that based on theoretical quantum mechanical calculations are attributed to halide-metal to ligand charge transfer (XMLCT). Through a combined experimental and computational approach, fundamental insight into the structure-property relationships within these Bi halide organic hybrid materials is provided.

Five novel tetravalent thorium (Th) compounds that consist of Th(H 2 O) x Cl y structural units were isolated from acidic aqueous solutions using a series of nitrogen-containing heterocyclic hydrogen (H) bond donors. Taken together with three previously reported phases, the compounds provide a series of monomeric Th IV complexes wherein the effects of noncovalent interactions (and H-bond donor identity) on Th structural chemistry can be examined. Seven distinct structural units of the general formulas [Th(H 2 O) x Cl 8- x ] x -4 ( x = 2, 4) and [Th(H 2 O) x Cl 9- x ] x -5 ( x = 5-7) are described. The complexes range from chloride-deficient [Th(H 2 O) 7 Cl 2 ] 2+ to chloride-rich [Th(H 2 O) 2 Cl 6 ] 2- species, and theory was used to understand the relative energies that separate complexes within this series via the stepwise chloride addition to an aquated Th cation. Electronic structure theory predicted the reaction energies of chloride addition and release of water through a series of transformations, generally highlighting an energetic driving force for chloride complexation. To probe the role of the counterion in the stabilization of these complexes, electrostatic potential (ESP) surfaces were calculated. The ESP surfaces indicated a dependence of the chloride distribution about the Th metal center on the p K a of the countercation, highlighting the directing effects of noncovalent interactions (e.g., Hbonding) on Th speciation.

Copper(II) alkynyl species are proposed as key intermediates in numerous Cu-catalyzed C-C coupling reactions. Supported by a β-diketiminate ligand, the three-coordinate copper(II) alkynyl [Cu II ]-C≡CAr (Ar = 2,6-Cl 2 C 6 H 3 ) forms upon reaction of the alkyne H-C≡CAr with the copper(II) tert -butoxide complex [Cu II ]-O t Bu. In solution, this [Cu II ]-C≡CAr species cleanly transforms to the Glaser coupling product ArC≡C-C≡CAr and [Cu I ](solvent). Addition of nucleophiles R'C≡C-Li (R' = aryl, silyl) and Ph-Li to [Cu II ]-C≡CAr affords the corresponding C sp -C sp and C sp -C sp2 coupled products RC≡C-C≡CAr and Ph-C≡CAr with concomitant generation of [Cu I ](solvent) and {[Cu I ]-C≡CAr} - , respectively. Supported by density functional theory (DFT) calculations, redox disproportionation forms [Cu III ](C≡CAr)(R) species that reductively eliminate R-C≡CAr products. [Cu II ]-C≡CAr also captures the trityl radical Ph 3 C· to give Ph 3 C-C≡CAr. Radical capture represents the key C sp -C sp3 bond-forming step in the copper-catalyzed C-H functionalization of benzylic substrates R-H with alkynes H-C≡CR' (R' = (hetero)aryl, silyl) that provide C sp -C sp3 coupled products R-C≡CR via radical relay with t BuOO t Bu as oxidant.

Three bismuth(iii)-organic compounds, [Bi4Cl8(PDC)2(phen)4]·2MeCN (1), [BiCl3(phen)2] (2), and [Bi2Cl6(terpy)2] (3), were prepared from solvothermal reactions of bismuth chloride, 2,6-pyridinedicarboxylic acid (H2PDC), and 1,10-phenanthroline (phen) or 2,2';6',2''-terpyridine (terpy). The structures were determined through single crystal X-ray diffraction and the compounds were further characterized via powder X-ray diffraction, Raman and infrared spectroscopy, and thermogravimetric analysis. The photoluminescence properties of the solid-state materials were assessed using steady state and time-dependent techniques to obtain excitation and emission profiles as well as lifetimes. The compounds exhibit visible emission ranging from the yellow-green to orange region upon UV excitation. Theoretical quantum mechanical calculations aimed at elucidating the observed emissive behavior show that the transitions can be assigned as predominantly ligand-to-ligand and ligand-to-metal charge transfer transitions. The solid-state structural chemistry, spectroscopic properties, and luminescence behavior of the bismuth compounds are presented herein.

S-Nitrosothiols (RSNOs) serve as air-stable reservoirs for nitric oxide in biology. While copper enzymes promote NO release from RSNOs by serving as Lewis acids for intramolecular electron-transfer, redox-innocent Lewis acids separate these two functions to reveal the effect of coordination on structure and reactivity. The synthetic Lewis acid B(C 6 F 5 ) 3 coordinates to the RSNO oxygen atom, leading to profound changes in the RSNO electronic structure and reactivity. Although RSNOs possess relatively negative reduction potentials, B(C 6 F 5 ) 3 coordination increases their reduction potential by over 1 V into the physiologically accessible +0.1 V vs. NHE. Outer-sphere chemical reduction gives the Lewis acid stabilized hyponitrite dianion trans-[LA-O-N=N-O-LA] 2- [LA=B(C 6 F 5 ) 3 ], which releases N 2 O upon acidification. Mechanistic and computational studies support initial reduction to the [RSNO-B(C 6 F 5 ) 3 ] radical anion, which is susceptible to N-N coupling prior to loss of RSSR., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of lanthanide organic hybrid materials was synthesized via hydrothermal methods and structurally characterized using single-crystal X-ray diffraction. Four phases were obtained from reactions of La, Eu, and Tb ions with 1,10-phenanthroline (phen) and 2-thiophenecarboxylate (TC): [La 2 (phen) 2 ( k 1 -TC) 2 (μ 2 -TC) 2 (η 3 -TC) 2 (H 2 O) 2 ] ( La-1/La-2 ), [Eu 2 (phen) 2 ( k 2 -TC) 2 (μ 2 -TC) 2 (η 3 -TC) 2 ]·2(H 2 O) ( Eu-3 ), and [Tb 2 (phen) 2 ( k 2 -TC) 2 (μ 2 -TC) 4 ]·2(H 2 O) ( Tb-4 ). Although each of the structures consists of homometallic ligand bridged dimers, the four distinct phases arise from subtle differences in ligand binding modes and supramolecular interactions. Ln doping was explored and resulted in analogous heterometallic systems, [Eu 2- x La x (phen) 2 ( k 2 -TC) 2 (μ 2 -TC) 2 (η 3 -TC) 2 ]·2(H 2 O) ( Eu 2- x La x -3 ; x = 0.47-1.51) and [Tb 2- y La y (phen) 2 ( k 2 -TC) 2 (μ 2 -TC) 4 ]·2(H 2 O) ( Tb 2- y La y -4 ; y = 0.42, 0.67). The photoluminescent properties of the solid-state materials were assessed using steady-state and time-dependent techniques to obtain excitation and emission profiles, transition energies, and lifetimes. The La phase exhibited ligand-based emission, whereas both Eu and Tb phases produced characteristic red and green metal-centered emission, respectively. By comparison, the heterometallic compounds exhibited both Ln- and ligand-based emission and photoluminescent color tuning of emission chromaticity. Further examination revealed that the color tuning was dependent on the relative La/Eu or La/Tb ratios as well as the excitation wavelength. These compounds are a rare example of single-phase Ln hybrid materials built from molecular units that exhibit excitation-dependent photoluminescent color tuning in the solid state.

Uranium(IV) complexation by 2-furoic acid (2-FA) was examined to better understand the effects of ligand identity and reaction conditions on species formation and stability. Five compounds were isolated: [UCl 2 (2-FA) 2 (H 2 O) 2 ] n (1), [U 4 Cl 10 O 2 (THF) 6 (2-FA) 2 ]⋅2 THF (2), [U 6 O 4 (OH) 4 (H 2 O) 3 (2-FA) 12 ]⋅7 THF⋅H 2 O (3), [U 6 O 4 (OH) 4 (H 2 O) 2 (2-FA) 12 ]⋅8.76 H 2 O (4), and [U 38 Cl 42 O 54 (OH) 2 (H 2 O) 20 ]⋅m H 2 O⋅n THF (5). The structures were determined by single-crystal X-ray diffraction and further characterized by Raman, IR, and optical absorption spectroscopy. The thermal stability and magnetic behavior of the compounds were also examined. Variations in the synthetic conditions led to notable differences in the structural units observed in the solid state. At low H 2 O/THF ratios, a tetranuclear oxo-bridged [U 4 O 2 ] core was isolated. Aging of this solution resulted in the formation a U 38 oxo cluster capped by chloro and water ligands. However, at increasing water concentrations only hexanuclear units were observed. In all cases, at temperatures of 100-120 °C, UO 2 nanoparticles formed., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the view of physiological significance, the transition-metal-mediated routes for nitrite (NO 2 - ) to nitric oxide (NO) conversion and phenol oxidation are of prime importance. Probing the reactivity of substituted phenols toward the nitritocopper(II) cryptate complex [ mC ]Cu(κ 2 - O 2 N)(ClO 4 ) ( 1a ), this report illustrates NO release from nitrite at copper(II) following a proton-coupled electron transfer (PCET) pathway. Moreover, a different protonated state of 1a with a proton hosted in the outer coordination sphere, [ mC H]Cu(κ 2 - O 2 N)(ClO 4 ) 2 ( 3 ), also reacts with substituted phenols via primary electron transfer from the phenol. Intriguingly, the alternative mechanism operative because of the presence of a proton at the remote site in 3 facilitates an unusual anaerobic pathway for phenol nitration.

Two thorium(IV) compounds, [Th(H 2 O) 4 Cl 4 ]·2(HPy·Cl) ( 1 ) and (HPy) 3 [Th 3 (H 2 O) 2 Cl 10 (OH) 5 ]·4(HPy·Cl) ( 2 ) (HPy = pyridinium), were isolated from acidic aqueous solution. The compounds were synthesized at room temperature and subsequently characterized using single crystal X-ray diffraction along with Raman and IR spectroscopies. Whereas compound 1 is built from discrete mononuclear Th(H 2 O) 4 Cl 4 units, compound 2 consists of a novel hydroxo-bridged trimeric [Th 3 (OH) 5 ] 7+ core. Such species are largely absent from discussions of Th solution and solid-state chemistry and their isolation may be attributed to outer coordination sphere interactions that help stabilize the structural units; extensive hydrogen bonding and π-π stacking interactions are present in 1 and 2 . Density functional theory calculations were performed to predict the respective vibrational frequencies of the structural units, and their relative stability was predicted at the correlated molecular theory level. Small-angle X-ray scattering analysis of [Th 3 (OH) 5 ] 7+ in water indicates that the trimeric structural unit remains intact and that it is indeed an important species that necessitates consideration in geochemical models and for design of Th materials from water.

A series of eighteen tetravalent actinide (An = Th, U, Pu) compounds were synthesized from acidic aqueous solutions containing thorium, uranium, or plutonium and a series of protonated nitrogen heterocycles. The compounds were characterized using Raman, IR, and optical absorption spectroscopies. The structures were determined using single-crystal X-ray diffraction and found to consist of [An(H 2 O) x Cl y ] 4- y ( x = 4-7 and y = 2-4) or AnCl 6 2- molecular units. Breaks in the structural chemistry of the early actinides were observed, with Th adopting exclusively Th-aquo-chloro species and Pu forming only PuCl 6 2- ; U crystallized as both U-aquo-chloro and UCl 6 2- . The relationship between the solid-state structural units and the solution species was interrogated using UV-vis-near-IR absorption spectroscopy. A comparison of the solution and solid-state spectra suggested that, although prevalent in the solid state, particularly for U and Pu, AnCl 6 2- does not exist to an appreciable extent in the reaction solution. Despite the identification of U-aquo-chloro species in solution, there are limited reports of these complexes in the solid state. Isolation of these unique actinide(IV) chlorides as reported in this work may point to the importance of nonbonding interactions in the stabilization and precipitation of An IV structural units.

A modular synthesis provides access to a series of new tris(pyrazolyl)borate ligands XpyMe TpK that possess a single functionalized pendant pyridyl (py) or pyrimidyl (pyd) arm designed to engage in tunable intramolecular H-bonding to metal-bound functionalities. To illustrate such H-bonding interactions, a series of [ XpyMe TpCu] 2 (μ-OH) 2 ( 6a - 6e ) complexes were synthesized from the corresponding XpyMe TpCu-OAc ( 5a - 5e ) complexes. Single crystal X-ray structures of three new dinuclear [ XpyMe TpCu] 2 (μ-OH) 2 complexes reveal H-bonding between the pendant heterocycle and bridging hydroxide ligands while the donor arm engages the copper center in an unusual monomeric DMAPMe TpCu-OH complex. Vibrational studies (IR) of each bridging hydroxide complex reveal reduced ν OH frequencies that tracks with the H-bond accepting ability of the pendant arm. Reversible protonation studies that interconvert [ XpyMe TpCu] 2 (μ-OH) 2 and [ XpyMe TpCu(OH 2 )]OTf species indicate that the acidity of the corresponding aquo ligand decreases with increasing H-bond accepting ability of the pendant arm.

Nitrate and nitrite anions have multifaceted impacts on the environment and human health. We herein report selective recognition of nitrite over nitrate anion inside the cavity of bimetallic azacryptates having p-xylyl spacers. This work reveals a number of binding interactions which play pivotal roles in nitrite anion recognition by rigid metal cryptates.

There is an increasing need for gadolinium-free magnetic resonance imaging (MRI) contrast agents, particularly for patients suffering from chronic kidney disease. Using a cluster-nanocarrier combination, we have identified a novel approach to the design of biomedical nanomaterials and report here the criteria for the cluster and the nanocarrier and the advantages of this combination. We have investigated the relaxivity of the following manganese oxo clusters: the parent cluster Mn 3 (O 2 CCH 3 ) 6 (Bpy) 2 (1) where Bpy = 2,2'-bipyridine and three new analogs, Mn 3 (O 2 CC 6 H 4 CH═CH 2 ) 6 (Bpy) 2 (2), Mn 3 (O 2 CC(CH 3 )═CH 2 ) 6 (Bpy) 2 (3), and Mn 3 O(O 2 CCH 3 ) 6 (Pyr) 2 (4) where Pyr = pyridine. The parent cluster, Mn 3 (O 2 CCH 3 ) 6 (Bpy) 2 (1), had impressive relaxivity ( r 1 = 6.9 mM -1 s -1 , r 2 = 125 mM -1 s -1 ) and was found to be the most amenable for the synthesis of cluster-nanocarrier nanobeads. Using the inverse miniemulsion polymerization technique (1) in combination with the hydrophilic monomer acrylamide, we synthesized nanobeads (∼125 nm diameter) with homogeneously dispersed clusters within the polyacrylamide matrix (termed Mn 3 Bpy-PAm). The nanobeads were surface-modified by co-polymerization with an amine-functionalized monomer. This enabled various postsynthetic modifications, for example, to attach a near-IR dye, Cyanine7, as well as a targeting agent. When evaluated as a potential multimodal MRI contrast agent, high relaxivity and contrast were observed with r 1 = 54.4 mM -1 s -1 and r 2 = 144 mM -1 s -1 , surpassing T 1 relaxivity of clinically used Gd-DTPA chelates as well as comparable T 2 relaxivity to iron oxide microspheres. Physicochemical properties, cellular uptake, and impacts on cell viability were also investigated.

Access to diverse, relatively high molecular weight soluble linear polymers without pendant solubilizing chains is the key to solution state synthesis of structurally diverse nanoribbons of conjugated materials. However, realizing soluble 1D-π-conjugated polymers without pendant solubilizing chains is a daunting task. Herein, inspired from the polypeptide β-strand architecture, we have designed and developed novel bifacial π-conjugated polymers ( M n : ca. 24 kDa) that are soluble ( ca. 70 to >250 mM) despite the absence of pendant solubilizing chains. The impact of varying the bifacial monomer height on polymer solubility, optical properties, and interactions with small molecules is reported.

Undirected C(sp 3 )-H functionalization reactions often follow site-selectivity patterns that mirror the corresponding C-H bond dissociation energies (BDEs). This often results in the functionalization of weaker tertiary C-H bonds in the presence of stronger secondary and primary bonds. An important, contemporary challenge is the development of catalyst systems capable of selectively functionalizing stronger primary and secondary C-H bonds over tertiary and benzylic C-H sites. Herein, we report a Cu catalyst that exhibits a high degree of primary and secondary over tertiary C-H bond selectivity in the amidation of linear and cyclic hydrocarbons with aroyl azides ArC(O)N 3 . Mechanistic and DFT studies indicate that C-H amidation involves H-atom abstraction from R-H substrates by nitrene intermediates [Cu](κ 2 -N,O-NC(O)Ar) to provide carbon-based radicals R . and copper(II)amide intermediates [Cu II ]-NHC(O)Ar that subsequently capture radicals R . to form products R-NHC(O)Ar. These studies reveal important catalyst features required to achieve primary and secondary C-H amidation selectivity in the absence of directing groups., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Linkage isomers of reduced metal-nitrosyl complexes serve as key species in nitric oxide (NO) reduction at monometallic sites to produce nitrous oxide (N 2 O), a potent greenhouse gas. While factors leading to extremely rare side-on nitrosyls are unclear, we describe a pair of nickel-nitrosyl linkage isomers through controlled tuning of noncovalent interactions between the nitrosyl ligands and differently encapsulated potassium cations. Furthermore, these reduced metal-nitrosyl species with N-centered spin density undergo radical coupling with free NO and provide a N-N coupled cis-hyponitrite intermediate whose protonation triggers the release of N 2 O. This report outlines a stepwise molecular mechanism of NO reduction to form N 2 O at a mononuclear metal site that provides insight into the related biological reduction of NO to N 2 O.

Three bismuth-2,5-thiophenedicarboxylates (Bi-TDC) and two europium-2,5-thiophenedicarboxylates (Eu-TDC) were synthesized under ambient conditions. The structures were determined through single crystal X-ray diffraction, and three of the phases were further characterized by powder X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. Reactions of bismuth nitrate, 2,5-thiophenedicarboxylate, and pyridine in an acidic solution of acetic acid and ethanol yield Hpy[Bi(TDC)2(H2O)]·1.5H2O (1), whereas reactions in a water/ethanol mixture produce a minor phase, [Hpy]3[Bi2(TDC)4(HTDC)(H2O)]·xH2O (2) along with a major product, (Hpy)2[Bi(TDC)2(HTDC)]·0.36H2O (3). The structures of 1-3 are all built from anionic Bi-TDC chains that are further bridged through additional TDC linkages into interpenetrated 2D sheets. Addition of an aqueous lanthanide solution to the reaction mixtures that yielded 1 and 2-3 resulted in the formation of doped phases, Hpy[Bi1-xLnx(TDC)2(H2O)]·1.5H2O (Bi1-xLnx-1), where Ln = Nd, Sm, Eu, Tb, Dy, and Yb, and (Hpy)2[Bi0.99Eu0.01 (TDC)2(HTDC)]·0.36H2O (Bi0.99Eu0.01-3). Using europium nitrate rather than the bismuth precursor resulted in the formation of two homometallic europium based phases, [Eu(TDC)(NO3)(H2O)]n (4) and [Eu2(TDC)3(H2O)9]·5H2O (5), which adopt an extended 3D network and an interpenetrated 2D structure, respectively. Photophysical measurements were carried out for 1 and the lanthanide containing phases and quantum yield and lifetime values were determined for the visible light emitters. Herein, the structural chemistry, spectroscopic properties, and luminescence of the bismuth phases, their lanthanide doped analogs, and the europium compounds are presented.

Organic ligands with carboxylate functionalities have been shown to affect the solubility, speciation, and overall chemical behavior of tetravalent metal ions. While many reports have focused on actinide complexation by relatively simple monocarboxylates such as amino acids, in this work we examined Th(IV) and U(IV) complexation by 4-hydroxybenzoic acid in water with the aim of understanding the impact that the organic backbone has on the solution and solid state structural chemistry of thorium(IV) and uranium(IV) complexes. Two compounds of the general formula [An 6 O 4 (OH) 4 (H 2 O) 6 (4-HB) 12 ]· nH 2 O [An = Th (Th-1) and U (U-1); 4-HB = 4-hydroxybenzoate] were synthesized via room-temperature reactions of AnCl 4 and 4-hydroxybenzoic acid in water. Solid state structures were determined by single-crystal X-ray diffraction, and the compounds were further characterized by Raman, infrared, and optical spectroscopies and thermogravimetry. The magnetism of U-1 was also examined. The structures of the Th and U compounds are isomorphous and are built from ligand-decorated oxo/hydroxo-bridged hexanuclear units. The relationship between the building units observed in the solid state structure of U-1 and those that exist in solution prior to crystallization as well as upon dissolution of U-1 in nonaqueous solvents was investigated using small-angle X-ray scattering, ultraviolet-visible optical spectroscopy, and dynamic light scattering. The evolution of U solution speciation as a function of reaction time and temperature was examined. Such effects as well as the impact of the ligand on the formation and evolution of hexanuclear U(IV) clusters to UO 2 nanoparticles compared to prior reported monocarboxylate ligand systems are discussed. Unlike prior reported syntheses of Th and U(IV) hexamers where the pH was adjusted to ∼2 and 3, respectively, to drive hydrolysis, hexamer formation with the HB ligand appears to be promoted only by the ligand.

A bismuth-organic compound containing 2,2':6'2"-terpyridine (terpy) and 2-thiophenecarboxylate (TC), of the general formula (terpy)Bi(κ 2 -TC) 3 ⋅0.47 H 2 O (BiOM-1), has been synthesized under hydrothermal conditions. Addition of a lanthanide nitrate solution to the reaction mixture led to statistical replacement of the bismuth centers, and yielded isomorphous lanthanide containing compounds Bi 1-x Ln x OM-1 (Ln=Nd, Sm, Eu, Tb, Dy, Er, and Yb) that showed bismuth and/or ligand sensitized lanthanide-centered emission, and the first example of NIR emission from a lanthanide doped BiOM. The structure was determined by single-crystal X-ray diffraction, and the level and uniformity of lanthanide ion incorporation into the bismuth host was determined by ICP-OES and electron microprobe analysis. For the visible emitters, lifetime data and quantum yields are presented. A high efficiency of sensitization was calculated for the europium analog (50.1 %), showing significant improvement over previously reported europium thiophenecarboxylates. These novel materials may provide strategies to address concerns over the long-term sustainability of the rare earth elements, especially relating to optical devices., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The whole mol-ecule of the title compound, C 20 H 14 O 6 , is generated by mirror symmetry, the mirror bis-ecting the central benzene ring. The carbonate groups adopt an s-cis-s-cis conformation, with torsion angles of 58.7 (2) and 116.32 (15)°. The crystal structure of 1,3-phenyl-ene bis-(phenyl carbonate) contains no strong hydrogen bonds, though weak C-H⋯O and offset π-π inter-actions are observed, forming layers parallel to the ac plane.

2,6-Diaminopyridine (26-DAP, C 5 H 7 N 3 ) is a common intermediate in the synthesis of aromatic azo chromophores, which are widespread in the dyes and pigments industry. Sublimation of commercial 26-DAP powder yielded a new polymorph, denoted Form II, which grew as colorless orthorhombic needles. Recrystallization from acetone or toluene also yielded Form II as the major phase. Thermal analysis shows that Form II is a less stable polymorph and it converts upon heating at 335 K to the previously reported Form I.

Well-defined metal nanocrystals play important roles in various fields, such as catalysis, medicine, and nanotechnology. They are often synthesized through kinetically controlled process in colloidal systems that contain metal precursors and surfactant molecules. The chemical functionality of surfactants as coordinating ligands to metal ions however remains a largely unsolved problem in this process. Understanding the metal-ligand complexation and its effect on formation kinetics at the molecular level is challenging but essential to the synthesis design of colloidal nanocrystals. Herein we report that spontaneous ligand replacement and anion exchange control the form of coordinated Pt-ligand intermediates in the system of platinum acetylacetonate [Pt(acac) 2 ], primary aliphatic amine, and carboxylic acid ligands. The formed intermediates govern the formation mode of Pt nanocrystals, leading to either a pseudo two-step or a one-step mechanism by switching on or off an autocatalytic surface growth. This finding shows the importance of metal-ligand complexation at the prenucleation stage and represents a critical step forward for the designed synthesis of nanocrystal-based materials.

The room temperature synthesis and structural characterization of two U(IV) compounds isolated from acidic aqueous solution is reported. Evaporation of a U(IV)/HCl solution containing pyridinium (HPy) yielded (HPy) 2 UCl 6 (1), yet in the presence of an organic carboxylate U(H 2 O) 4 Cl 4 ·(HPy·Cl) 2 (2) is obtained. The structures have been determined by single crystal X-ray diffraction and characterized by Raman, IR, and optical spectroscopies. The magnetism of both compounds was also investigated. The structure of 1 is built from UCl 6 2- anionic units, pervasive in descriptions of the aqueous chemistry of tetravalent uranium, and is found to undergo a phase transition from C2/m to P1̅ upon cooling. By comparison, the structure of 2 contains a neutral U(IV)-aquo-chloro complex, U(H 2 O) 4 Cl 4 , for which there is no literature precedence. Density functional theory calculations were performed to predict the geometries, vibrational frequencies, and relative energetics of the UCl 6 2- and U(H 2 O) 4 Cl 4 units. The energetics of the reaction of U(H 2 O) 4 Cl 4 to form the dianion are predicted to be exothermic in the gas phase and in aqueous solution. The predicted energetics coupled with no previous solid state reports of a U(IV)-aquo-chloro complex may point toward the importance of hydrogen bonding and other supramolecular interactions, prevalent in the structures of 1 and 2, on the stabilization and/or crystallization of the U(H 2 O) 4 Cl 4 structural unit.

The crystal structures of two new bimetallic uranyl-transition metal compounds with diglycolic acid [or 2-(carboxymethoxy)acetic acid] have been hydrothermally synthesized and structurally characterized via single-crystal X-ray diffraction. The compounds, namely catena-poly[[[tetraaquamanganese(II)]-μ-2,2'-oxydiacetato-[dioxidouranium(VI)]-μ-2,2'-oxydiacetato] dihydrate], {[MnU(C 4 H 4 O 5 ) 2 O 2 (H 2 O) 4 ]·2H 2 O} n , and catena-poly[[[tetraaquacobalt(II)]-μ-2,2'-oxydiacetato-[dioxidouranium(VI)]-μ-2,2'-oxydiacetato] dihydrate], {[CoU(C 4 H 4 O 5 ) 2 O 2 (H 2 O) 4 ]·2H 2 O} n , both crystallize in the triclinic space group P-1. These compounds form one-dimensional chains via alternating uranyl and transition metal building units. The chains then assemble into three-dimensional supramolecular networks through several hydrogen bonds between water molecules and diglycolate ligands. Luminescence measurements were conducted and no uranyl emission was observed in either compound.

Copper(II) aryl species are proposed key intermediates in Cu-catalyzed cross-coupling reactions. Novel three-coordinate copper(II) aryls [Cu II ]-C 6 F 5 supported by ancillary β-diketiminate ligands form in reactions between copper(II) alkoxides [Cu II ]-O t Bu and B(C 6 F 5 ) 3 . Crystallographic, spectroscopic, and DFT studies reveal geometric and electronic structures of these Cu(II) organometallic complexes. Reaction of [Cu II ]-C 6 F 5 with the free radical NO (g) results in C-N bond formation to give [Cu](η 2 -ONC 6 F 5 ). Remarkably, addition of the phenolate anion PhO - to [Cu II ]-C 6 F 5 directly affords diaryl ether PhO-C 6 F 5 with concomitant generation of the copper(I) species [Cu I ](solvent) and {[Cu I ]-C 6 F 5 } - . Experimental and computational analysis supports redox disproportionation between [Cu II ]-C 6 F 5 and {[Cu II ](C 6 F 5 )(OPh)} - to give {[Cu I ]-C 6 F 5 } - and [Cu III ](C 6 F 5 )(OPh) unstable toward reductive elimination to [Cu I ](solvent) and PhO-C 6 F 5 .

The paper describes three methods for the preparation of methoxysiloxide complexes, a rare class of complexes of relevance to room temperature vulcanization (RTV) of polysiloxanes. The salt metathesis reaction involves the use of the recently described reagent NaOSi(OMe) 2 Me with various metal chlorides to give Cp* 2 Ti[OSi(OMe) 2 Me](OMe), ( Me,Me N 2 N)NiOSi(OMe) 2 Me, (IPr)CuOSi(OMe) 2 Me, and (triphos)CoOSi(OMe) 2 Me (Cp* = C 5 Me 5 , triphos = Me(CH 2 PPh 2 ) 3 ). Several attempted reactions gave methoxide complexes instead, a pathway that is attributed to the intermediacy of κ 2 -OSi(OMe) 2 Me species. The diol Cp* 2 Zr(OH) 2 reacts with excess (MeO) 3 SiMe to give Cp* 2 Zr[OSi(OMe) 2 Me] 2 . In contrast the less nucleophilic Cp* 2 Ti(OH) 2 was unreactive. The third route to methoxysiloxide complexes involves the reaction of Cp* 2 M(O)(py) with (MeO) 3 SiMe to give Cp* 2 M[OSi(OMe) 2 Me](OMe) in nearly quantitative yield (M = Ti, Zr). The structures of Cp* 2 Ti[OSi(OMe) 2 Me](OMe), Cp* 2 Zr[OSi(OMe) 2 Me](OMe), (IPr)CuOSi(OMe) 2 Me, and (triphos)CoOSi(OMe) 2 Me were confirmed by single crystal X-ray diffraction.

We report herein three new modes of reactivity between arylazides N 3 Ar with a bulky copper(I) β-diketiminate. Addition of N 3 Ar X3 (Ar X3 =2,4,6-X 3 C 6 H 2 ; X=Cl or Me) to [ i Pr 2 NN]Cu(NCMe) results in triazenido complexes from azide attack on the β-diketiminato backbone. Reaction of [ i Pr 2 NN]Cu(NCMe) with bulkier azides N 3 Ar leads to terminal nitrenes [ i Pr 2 NN]Cu]=NAr that dimerize via formation of a C-C bond at the arylnitrene p-position to give the dicopper(II) diketimide 4 (Ar=2,6- i Pr 2 C 6 H 3 ) or undergo nitrile insertion to give diazametallocyclobutene 8 (Ar=4-Ph-2,6-iPr 2 C 6 H 2 ). Importantly, reactivity studies reveal both 4 and 8 to be "masked" forms of the terminal nitrenes [ i Pr 2 NN]Cu=NAr that undergo nitrene group transfer to PMe 3 , t BuNC, and even into a benzylic sp 3 C-H bond of ethylbenzene., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Supramolecular crystalline assembly constitutes a rational approach to bioengineer intracellular structures. Here, biocrystals of clofazimine (CFZ) that form in vivo within macrophages were measured to have marked curvature. Isolated crystals, however, showed reduced curvature suggesting that intracellular forces bend these drug crystals. Consistent with the ability of biocrystals to elastically deform, the inherent crystal structure of the principal molecular component of the biocrystals-the hydrochloride salt of CFZ (CFZ-HCl)-has a corrugated packing along the (001) face and weak dispersive bonding in multiple directions. These characteristics were previously found to be linked to the elasticity of other organic crystals. Internal stress in bent CFZ-HCl led to photoelastic effects on the azimuthal orientation of polarized light transmittance. We propose that elastic, intracellular crystals can serve as templates to construct functional microdevices with different applications., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nitrite (NO 2 - ) and nitroso compounds (E-NO, E = RS, RO, and R 2 N) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper(II) nitrito complex [Cl 2 NN F6 ]Cu(κ 2 -O 2 N)·THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu II ](κ 2 -O 2 N) that leads to S-nitrosation to give the S-nitrosothiol RSNO and copper(II) hydroxide [Cu II ]-OH. This nitrosation pathway is general and results in the nitrosation of the amine Ph 2 NH and alcohol t BuOH to give Ph 2 NNO and t BuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper(II) thiolate [Cu II ]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu II ]-OH.