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1. Solid Decolorization: Dismantling of an Orange‐Red Zwitterionic Cocrystal by Multicomponent Milling

   https://doi.org/10.1002/adom.202400889  

   Ezekiel, Charles_Izuchukwu; Ortiz‐de_León, Celymar; Reinheimer, Eric; MacGillivray, Leonard_R (May 2024, Advanced Optical Materials)

   Abstract An application of multi‐component milling is described to achieve a decolorization by dismantling the orange‐red zwitterionic cocrystal (PDA)∙(APAP) (wherePDA= 2,4‐pyridinedicarboxylic acid,APAP= acetaminophen) usingn,n′‐BPE(BPE=trans‐1,2‐bis(n‐pyridylethylene and forn=n′ = 3 or 4). Each ofn,n′‐BPEforms a colorless hydrogen‐bonded cocrystal withPDA. 

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2. Cationic Bis(Gold) Indenyl Complexes

   https://doi.org/10.1002/cplu.202300691  

   Slinger, Brady_L; Zhu, Jiaqi; Widenhoefer, Ross_A (February 2024, ChemPlusChem)

   Abstract Reaction of (P)AuOTf [P=P(t‐Bu)₂o‐biphenyl] with indenyl‐ or 3‐methylindenyl lithium led to isolation of gold η¹‐indenyl complexes (P)Au(η¹‐inden‐1‐yl) (1 a) and (P)Au(η¹‐3‐methylinden‐1‐yl) (1 b), respectively, in >65 % yield. Whereas complex1 bis static, complex1 aundergoes facile, degenerate 1,3‐migration of gold about the indenyl ligand (ΔG^≠_153K=9.1±1.1 kcal/mol). Treatment of complexes1 aand1 bwith (P)AuNTf₂led to formation of the corresponding cationic bis(gold) indenyl complexestrans‐[(P)Au]₂(η¹,η¹‐inden‐1,3‐yl) (2 a) andtrans‐[(P)Au]₂(η¹,η²‐3‐methylinden‐1‐yl) (2 b), respectively, which were characterized spectroscopically and modeled computationally. Despite the absence of aurophilic stabilization in complexes2 aand2 b, the binding affinity of mono(gold) complex1 atoward exogenous (P)Au⁺exceed that of free indene by ~350‐fold and similarly the binding affinity of1 btoward exogenous (P)Au⁺exceed that of 3‐methylindene by ~50‐fold. The energy barrier for protodeauration of bis(gold) indenyl complex2 awith HOAc was ≥8 kcal/mol higher than for protodeauration of mono(gold) complex1 a. 

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3. Isolation of an Elusive Phosphametallacyclobutadiene and Its Role in Reversible Carbon−Carbon Bond Cleavage

   https://doi.org/10.1002/anie.202203073  

   Jakhar, Vineet K.; Esper, Alec M.; Ghiviriga, Ion; Abboud, Khalil A.; Ehm, Christian; Veige, Adam S. (June 2022, Angewandte Chemie International Edition)

   Abstract The reactivity of phosphaalkynes, the isolobal and isoelectronic congeners to alkynes, with metal alkylidyne complexes is explored in this work. Treating the tungsten alkylidyne [^tBuOCO]W≡C^tBu(THF)₂(1) with phosphaalkyne (10) results in the formation of [O₂C(^tBuC=)W{η²‐(P,C)−P≡C−Ad}(THF)] (13‐^tBu_THF) and [O₂C(AdC=)W{η²‐(P,C)−P≡C−^tBu}(THF)] (13‐Ad_THF); derived from the formal reductive migratory insertion of the alkylidyne moiety into a W−C_arenebond. Analogous to alkyne metathesis, a stable phosphametallacyclobutadiene complex [^tBuOCO]W[κ²‐C(^tBu)PC(Ad)] (14) forms upon loss of THF from the coordination sphere of either13‐^tBu_THFor13‐Ad_THF. Remarkably, the C−C bonds reversibly form/cleave with the addition or removal of THF from the coordination sphere of the formal tungsten(VI) metal center, permitting unprecedented control over the transformation of a tetraanionic pincer to a trianionic pincer and back. Computational analysis offers thermodynamic and electronic reasoning for the reversible equilibrium between13‐^tBu/Ad_THFand14. 

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4. Molecules that Turn Themselves Inside‐Out: Tuning in / out Equilibria and Homeomorphic Isomerization in Macrobicyclic Dibridgehead Diphosphines P((CH ₂ ) _n ) ₃ P Newly Accessible by Earth‐Abundant‐Metal Templates

   https://doi.org/10.1002/chem.202302200  

   Zarcone, Samuel_R; Bhuvanesh, Nattamai; Gladysz, John_A (November 2023, Chemistry – A European Journal)

   Abstract Photolyses oftrans‐Fe(CO)₃(P((CH₂)_n)₃P) (n=10 (a), 12 (b), 14 (c), 16 (d), 18 (e)) in the presence of PMe₃provide the first economical and scalable route to macrobicyclic dibridgehead diphosphines P((CH₂)_n)₃P (1). These are isolated as mixtures ofin,in/out,outisomers that equilibrate with degeneratein,out/out,inisomers at 150 °C via pyramidal inversion at phosphorus. For the entire series, VT³¹P NMR data establish or boundK_eq, rates, and activation parameters for a variety of phenomena, many of which involve homeomorphic isomerizations, topological processes by which certain molecules can turn themselves inside out (e. g.,in,in⇌out,out). This provides the first detailed mapping of such trends in homologous series of aliphatic bicyclic compounds XE((CH₂)_n)₃EX with any type of bridgehead. Isomeric diborane adducts1 a,d ⋅ 2BH₃are also characterized. Crystal structures ofout,out‐1 aandin,in‐1 a ⋅ 2BH₃aid isomer assignments and reveal unusual cage conformations. 

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5. Perfect Polar Alignment of Parallel Beloamphiphile Layers: Improved Structural Design Bias Realized in Ferroelectric Crystals of the Novel “Methoxyphenyl Series of Acetophenone Azines”

   https://doi.org/10.1002/chem.202400182  

   Bhoday, Harmeet; Knotts, Nathan; Glaser, Rainer (May 2024, Chemistry – A European Journal)

   Abstract An improved design is described for ferroelectric crystals and implemented with the “methoxyphenyl series” of acetophenone azines, (MeO−Ph, Y)‐azines with Y = F (1), Cl (2), Br (3), or I (4). The crystal structures of these azines exhibit polar stacking of parallel beloamphiphile monolayers (PBAMs). Azines 1, 3, and 4 form true racemates whereas chloroazine 2 crystallizes as a kryptoracemate. Azines 1–4 are helical because of the N−N bond conformation. In true racemates the molecules of opposite helicity (M and P) are enantiomers A(M) and A*(P) while in kryptoracemates they are diastereomers A(M) and B*(P). The stacking mode of PBAMs is influenced by halogen bonding, with 2–4 showcasing a kink due to directional interlayer halogen bonding, whereas fluoroazine 1demonstrates ideal polar stacking by avoiding it. Notably, (MeO−Ph, Y)‐azines display a stronger bias for dipole parallel alignment, attributed to the linearity of the biphenyl moiety as compared to the phenoxy series of (PhO, Y)‐azines with their non‐linear Ph−O−Ph moiety. The crystals of 1–4 all feature planar biphenyls and this synthon facilitates their crystallization through potent triple T‐contacts and enhances their nonlinear optical (NLO) performance by increasing conjugation length and affecting favorable chromophore conformations in the solids. 

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