Rational Design of Specific Recognition Molecules for Simultaneously Monitoring of Endogenous Polysulfide and Hydrogen Sulfide in the Mouse Brain

A biosensor was created for the simultaneous monitoring of endogenous H₂S_n and H₂S in mouse brains and exploring their roles in activation of the TRPA1 channel under two types of brain disease models: ischemia and Alzheimer's disease (AD). Based on DFT calculations and electrochemical measurements, two probes, 3,4‐bis((2‐fluoro‐5‐nitrobenzoyl)oxy)‐benzoic acid (M_PS‐1) and N‐(4‐(2,5‐dinitrophenoxy) phenyl)‐5‐(1, 2‐dithiolan‐3‐yl)pentanamide (M_HS‐1), were synthesized for specific recognition of H₂S_n and H₂S. Through co‐assembly of the two probes at the mesoporous gold film with good anti‐biofouling ability and electrocatalytic activity, this microsensor showed high selectivity for H₂S_n and H₂S against potential biological interferences. The biosensor can simultaneously determine the concentration of H₂S_n from 0.2 to 50 μm , as well as that of H₂S from 0.2 to 40 μm . The expression of TRPA1 protein positively correlated with levels of H₂S_n under both ischemia and AD.     

A Single Fluorescent Probe to Visualize Hydrogen Sulfide and Hydrogen Polysulfides with Different Fluorescence Signals

Hydrogen sulfide (H₂S) and hydrogen polysulfides (H₂S_n, n>1) are endogenous regulators of many physiological processes. In order to better understand the symbiotic relationship and cellular cross‐talk between H₂S and H₂S_n, it is highly desirable to develop single fluorescent probes which enable dual‐channel discrimination between H₂S and H₂S_n. Herein, we report the rational design, synthesis, and evaluation of the first dual‐detection fluorescent probe DDP‐1 that can visualize H₂S and H₂S_n with different fluorescence signals. The probe showed high selectivity and sensitivity to H₂S and H₂S_n in aqueous media and in cells.     

Absolute configuration of strictosidinic acid

The absolute configuration of strictosidinic acid, (2S,3R,4S)‐3‐ethenyl‐2‐(β‐d ‐glucopyranosyloxy)‐4‐{[(1S)‐2,3,4,9‐tetrahydro‐1H‐pyrido[3,4‐b]indol‐1‐yl]methyl}‐3,4‐dihydro‐2H‐pyran‐5‐carboxylate, was determined from its sodium chloride trihydrate, poly[[diaqua((2S,3R,4S)‐3‐ethenyl‐2‐(β‐d ‐glucopyranosyloxy)‐4‐{[(1S)‐2,3,4,9‐tetrahydro‐1H‐pyrido[3,4‐b]indol‐2‐ium‐1‐yl]methyl}‐3,4‐dihydro‐2H‐pyran‐5‐carboxylate)sodium] chloride monohydrate], {[Na(C₂₆H₃₂N₂O₉)(H₂O)₂]Cl·H₂O}_n. The strictosidinic acid molecule participates in intermolecular hydrogen bonds of the O—H...O and O—H...Cl types. The solid‐state conformation was observed as a zwitterion, based on a charged pyridine N atom and a carboxylate group, the latter mediating the packing through coordination with the sodium cation.     

Chiral one‐ and two‐dimensional silver(I)–biotin coordination polymers

Reaction of biotin {C₁₀H₁₆N₂O₃S, HL; systematic name: 5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoic acid} with silver acetate and a few drops of aqueous ammonia leads to the deprotonation of the carboxylic acid group and the formation of a neutral chiral two‐dimensional polymer network, poly[[{μ₃‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}silver(I)] trihydrate], {[Ag(C₁₀H₁₅N₂O₃S)]·3H₂O}_n or {[Ag(L)]·3H₂O}_n, (I). Here, the Ag^I cations are pentacoordinate, coordinated by four biotin anions via two S atoms and a ureido O atom, and by two carboxylate O atoms of the same molecule. The reaction of biotin with silver salts of potentially coordinating anions, viz. nitrate and perchlorate, leads to the formation of the chiral one‐dimensional coordination polymers catena‐poly[[bis[nitratosilver(I)]‐bis{μ₃‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] monohydrate], {[Ag₂(NO₃)₂(C₁₀H₁₆N₂O₃S)₂]·H₂O}_n or {[Ag₂(NO₃)₂(HL)₂]·H₂O}_n, (II), and catena‐poly[bis[perchloratosilver(I)]‐bis{μ₃‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}], [Ag₂(ClO₄)₂(C₁₀H₁₆N₂O₃S)₂]_n or [Ag₂(ClO₄)₂(HL)₂]_n, (III), respectively. In (II), the Ag^I cations are again pentacoordinated by three biotin molecules via two S atoms and a ureido O atom, and by two O atoms of a nitrate anion. In (I), (II) and (III), the Ag^I cations are bridged by an S atom and are coordinated by the ureido O atom and the O atoms of the anions. The reaction of biotin with silver salts of noncoordinating anions, viz. hexafluoridophosphate (PF₆⁻) and hexafluoridoantimonate (SbF₆⁻), gave the chiral double‐stranded helical structures catena‐poly[[silver(I)‐bis{μ₂‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] hexafluoridophosphate], {[Ag(C₁₀H₁₆N₂O₃S)₂](PF₆)}_n or {[Ag(HL)₂](PF₆)}_n, (IV), and catena‐poly[[[{5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}silver(I)]‐μ₂‐{5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] hexafluoridoantimonate], {[Ag(C₁₀H₁₆N₂O₃S)₂](SbF₆)}_n or {[Ag(HL)₂](SbF₆)}_n, (V), respectively. In (IV), the Ag^I cations have a tetrahedral coordination environment, coordinated by four biotin molecules via two S atoms, and by two carboxy O atoms of two different molecules. In (V), however, the Ag^I cations have a trigonal coordination environment, coordinated by three biotin molecules via two S atoms and one carboxy O atom. In (IV) and (V), neither the ureido O atom nor the F atoms of the anion are involved in coordination. Hence, the coordination environment of the Ag^I cations varies from AgS₂O trigonal to AgS₂O₂ tetrahedral to AgS₂O₃ square‐pyramidal. The conformation of the valeric acid side chain varies from extended to twisted and this, together with the various anions present, has an influence on the solid‐state structures of the resulting compounds. The various O—H...O and N—H...O hydrogen bonds present result in the formation of chiral two‐ and three‐dimensional networks, which are further stabilized by C—H...X (X = O, F, S) interactions, and by N—H...F interactions for (IV) and (V). Biotin itself has a twisted valeric acid side chain which is involved in an intramolecular C—H...S hydrogen bond. The tetrahydrothiophene ring has an envelope conformation with the S atom as the flap. It is displaced from the mean plane of the four C atoms (plane B) by 0.8789 (6) Å, towards the ureido ring (plane A). Planes A and B are inclined to one another by 58.89 (14)°. In the crystal, molecules are linked via O—H...O and N—H...O hydrogen bonds, enclosing R₂²(8) loops, forming zigzag chains propagating along [001]. These chains are linked via N—H...O hydrogen bonds, and C—H...S and C—H...O interactions forming a three‐dimensional network. The absolute configurations of biotin and complexes (I), (II), (IV) and (V) were confirmed crystallographically by resonant scattering.     

SN1‐SN2 and SN2‐SN3 mechanistic changes revealed by transition states of the hydrolyses of benzyl chlorides and benzenesulfonyl chlorides

Hydrolysis reactions of benzyl chlorides and benzenesulfonyl chlorides were theoretically investigated with the density functional theory method, where the water molecules are explicitly considered. For the hydrolysis of benzyl chlorides (para‐Z? C₆H₄? CH₂? Cl), the number of water molecules (n) slightly influences the transition‐state (TS) structure. However, the para‐substituent (Z) of the phenyl group significantly changes the reaction process from the stepwise (S_N1) to the concerted (S_N2) pathway when it changes from the typical electron‐donating group (EDG) to the typical electron‐withdrawing one (EWG). The EDG stabilizes the carbocation (MeO? C₆H₄? CH₂⁺), which in turn makes the S_N1 mechanism more favorable and vice versa. For the hydrolysis of benzenesulfonyl chlorides (para‐Z? C₆H₄? SO₂? Cl), both the Z group and n influence the TS structure. For the combination of the large n value (n > 9) and EDG, the S_N2 mechanism was preferred. Conversely, for the combination of the small n value and EWG, the S_N3 one was more favorable. © 2014 Wiley Periodicals, Inc.     

Temperature‐induced solid‐to‐solid transformation in helical homochiral coordination polymers

The reactions of (R)‐ and (S)‐4‐(1‐carboxyethoxy)benzoic acid (H₂CBA) with 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene (1,3‐BMIB) ligands afforded a pair of homochiral coordination polymers (CPs), namely, poly[[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(S)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] monohydrate], {[Zn(C₁₀H₈O₅)(C₁₄H₁₄N₄)]·H₂O}_n or {[Zn{(S)‐CBA}(1,3‐BMIB)]·H₂O}_n ( 1‐L ), and poly[[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(R)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] monohydrate] ( 1‐D ). Three kinds of helical chains exist in compounds 1‐D and 1‐L , which are constructed from Zn^II atoms, 1,3‐BMIB ligands and/or CBA^2? ligands. When the as‐synthesized crystals of 1‐L and 1‐D were further heated in the mother liquor or air, poly[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(S)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)], [Zn(C₁₀H₈O₅)(C₁₄H₁₄N₄)]_n or [Zn{(S)‐CBA}(1,3‐BMIB)]_n ( 2‐L ), and poly[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(R)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] ( 2‐D ) were obtained, respectively. The single‐crystal structure analysis revealed that 2‐L and 2‐D only contained one type of helical chain formed by Zn^II atoms and 1,3‐BMIB and CBA^2? ligands, which indicated that the helical chains were reconstructed though solid‐to‐solid transformation. This result not only means the realization of helical transformation, but also gives a feasible strategy to build homochiral CPs.     

Soft scorpionate coordination at alkali metals

Reported here are the single‐crystal X‐ray structure analyses of bis‐μ‐methanol‐κ⁴O:O‐bis{[hydrotris(3‐phenyl‐2‐sulfanylidene‐2,3‐dihydro‐1H‐1,3‐imidazol‐1‐yl)borato‐κ³H,S,S′](methanol‐κO)sodium(I)}, [Na₂(C₂₇H₂₂BN₆S₃)₂(CH₄O)₄] (NaTm^Ph), bis‐μ‐methanol‐κ⁴O:O‐bis{[hydrotris(3‐isopropyl‐2‐sulfanylidene‐2,3‐dihydro‐1H‐1,3‐imidazol‐1‐yl)borato‐κ³H,S,S′](methanol‐κO)sodium(I)}–diethyl ether–methanol (1/0.3333/0.0833), [Na₂(C₁₈H₂₈BN₆S₃)₂(CH₄O)₄]·0.3333C₄H₁₀O·0.0833CH₃OH (NaTm^iPr), and a novel anhydrous form of sodium hydrotris(methylthioimidazolyl)borate, poly[[μ‐hydrotris(3‐methyl‐2‐sulfanylidene‐2,3‐dihydro‐1H‐1,3‐imidazol‐1‐yl)borato]sodium(I)], [Na(C₁₂H₁₆BN₆S₃)] ([NaTm^Me]_n). NaTm^iPr and NaTm^Ph have similar dimeric molecular structures with κ³H,S,S′‐bonding, but they differ in that NaTm^Ph is crystallographically centrosymmetric (Z′ = 0.5) while NaTm^iPr contains one crystallographically centrosymmetric dimer and one dimer positioned on a general position (Z′ = 1.5). [NaTm^Me]_n is a one‐dimensional coordination polymer that extends along the a direction and which contains a hitherto unseen side‐on η²‐C=S‐to‐Na bond type. An overview of the structural preferences of alkali metal soft scorpionate complexes is presented. This analysis suggests that these thione‐based ligands will continue to be a rich source of interesting alkali metal motifs worthy of isolation and characterization.     

Light‐Induced Rearrangement of Thioether‐Substituted Phosphanide Ligands: Scope and Limitations of a Remarkable Isomerization

Treatment of the thioether‐substituted secondary phosphanes R²PH(C₆H₄‐2‐SR¹) [R²=(Me₃Si)₂CH, R¹=Me ( 1_PH ), iPr ( 2_PH ), Ph ( 3_PH ); R²=tBu, R¹=Me ( 4_PH ); R²=Ph, R¹=Me ( 5_PH )] with nBuLi yields the corresponding lithium phosphanides, which were isolated as their THF ( 1 – 5_Pa ) and tmeda ( 1 – 5_Pb ) adducts. Solid‐state structures were obtained for the adducts [R²P(C₆H₄‐2‐SR¹)]Li(L)_n [R²=(Me₃Si)₂CH, R¹=nPr, (L)_n=tmeda ( 2_Pb ); R²=(Me₃Si)₂CH, R¹=Ph, (L)_n=tmeda ( 3_Pb ); R²=Ph, R¹=Me, (L)_n=(THF)_1.33 ( 5_Pa ); R²=Ph, R¹=Me, (L)_n=([12]crown‐4)₂ ( 5_Pc )]. Treatment of 1_PH with either PhCH₂Na or PhCH₂K yields the heavier alkali metal complexes [{(Me₃Si)₂CH}P(C₆H₄‐2‐SMe)]M(THF)_n [M=Na ( 1_Pd ), K ( 1_Pe )]. With the exception of 2_Pa and 2_Pb , photolysis of these complexes with white light proceeds rapidly to give the thiolate species [R²P(R¹)(C₆H₄‐2‐S)]M(L)_n [M=Li, L=THF ( 1_Sa , 3_Sa – 5_Sa ); M=Li, L=tmeda ( 1_Sb , 3_Sb – 5_Sb ); M=Na, L=THF ( 1_Sd ); M=K, L=THF ( 1_Se )] as the sole products. The compounds 3_Sa and 4_Sa may be desolvated to give the cyclic oligomers [[{(Me₃Si)₂CH}P(Ph)(C₆H₄‐2‐S)]Li]₆ (( 3_S )₆) and [[tBuP(Me)(C₆H₄‐2‐S)]Li]₈ (( 4_S )₈), respectively. A mechanistic study reveals that the phosphanide–thiolate rearrangement proceeds by intramolecular nucleophilic attack of the phosphanide center at the carbon atom of the substituent at sulfur. For 2_Pa / 2_Pb , competing intramolecular β‐deprotonation of the n‐propyl substituent results in the elimination of propene and the formation of the phosphanide–thiolate dianion [{(Me₃Si)₂CH}P(C₆H₄‐2‐S)]^2?.     

α‐Tetraphosphorus Trichalcogenide Diamides and Imides containing both Sulfur and Selenium

Reaction of a mixture of bicyclic phosphorus sulfide selenide iodides α‐P₄S_nSe_3−nI₂ (n = 0–3) with PrⁱNH₂ and Et₃N gave corresponding diamides α‐P₄S_nSe_3−n(NHPrⁱ)₂ (n = 0–3) and imides α‐P₄S_nSe_3−n(μ‐NPrⁱ) (n = 2–3), identified in solution by ³¹P NMR. In one isomer of α‐P₄S₂Se(μ‐NPrⁱ), the C₂ symmetry of imides such as α‐P₄S₃(μ‐NPrⁱ) was broken, allowing relative assignment of ²J NMR couplings to the PNP bridge and the PSP bridge opposite to it. The coupling through the sulfur bridge was found to be reduced to ca. zero, in contrast to previous assumptions for this class of compounds. Ab initio models were calculated at the MPW1PW91/svp level for the sulfide selenide imides and for a selection of bond rotamers of the diamides, and at the MPW1PW91/LanL2DZ(d) level for the sulfide selenide diiodides. Different skeletal isomers were prevalent for the mixed chalcogenide diamides than for the diiodides, showing that exchange of chalcogen between skeletal positions took place in the amination reaction even at room temperature. Similar differences to those observed were predicted by the models, suggesting that equilibrium was attained.     

Multiple‐State Emissions from Neat,Single‐Component Molecular Solids: Suppression of Kasha's Rule

Three rigid and structurally simple heterocyclic stilbene derivatives, (E)‐3H,3′H‐[1,1′‐biisobenzofuranylidene]‐3,3′‐dione, (E)‐3‐(3‐oxobenzo[c] thiophen‐1(3H)‐ylidene)isobenzofuran‐1(3H)‐one, and (E)‐3H,3′H‐[1,1′‐bibenzo[c] thiophenylidene]‐3,3′‐dione, are found to fluoresce in their neat solid phases, from upper (S₂) and lowest (S₁) singlet excited states, even at room temperature in air. Photophysical studies, single‐crystal structures, and theoretical calculations indicate that large energy gaps between S₂ and S₁ states (T₂ and T₁ states) as well as an abundance of intra and intermolecular hydrogen bonds suppress internal conversions of the upper excited states in the solids and make possible the fluorescence from S₂ excited states (phosphorescence from T₂ excited states). These results, including unprecedented fluorescence quantum yields (2.3–9.6 %) from the S₂ states in the neat solids, establish a unique molecular skeleton for achieving multi‐colored emissions from upper excited states by “suppressing” Kasha's rule.     

Studies on the Magnetic Ground State of a Spin Möbius Strip

Here we report the synthesis, structure and detailed characterisation of three n‐membered oxovanadium rings, Na_n[(V=O)_nNa_n(H₂O)_n(α, β, or γ‐CD)₂]?m H₂O (n=6, 7, or 8), prepared by the reactions of (V=O)SO₄?x H₂O with α, β, or γ‐cyclodextrins (CDs) and NaOH in water. Their alternating heterometallic vanadium/sodium cyclic core structures were sandwiched between two CD moieties such that O‐Na‐O groups separated the neighbouring vanadyl ions. Antiferromagnetic interactions between the S=1/2 vanadyl ions led to S=0 ground states for the even‐membered rings, but to two quasi‐degenerate S=1/2 states for the spin‐frustrated heptanuclear cluster.     

Syntheses,Structures, and Catalytic Reactions of Palladium Adducts of Chiral Diphosphines That Contain a Rhenium Stereocenter in the Backbone

Reactions of the title diphosphines [(η⁵‐C₅H₄PPh₂)Re(NO)(PPh₃)((CH₂)_nPPh₂)] (n=0, (R)‐ 1 ; n=1, racemic or (S)‐ 2 ) with [PdCl₂(PhCN)₂] give the palladium/rhenium chelate complexes [(η⁵‐C₅H₄PPh₂)Re(NO)(PPh₃)((μ‐CH₂)_nPPh₂)PdCl₂] (n=0, (S)‐ 5 ; n=1, racemic or (S)‐ 6 ) in 75–92% yield. The crystal structure of racemic 6 shows a twisted‐boat conformation of the chelate ring, giving a chiral pocket very different from that in a related rhodium chelate. However, NOE experiments suggest a similar ensemble of conformations in solution. Catalysts are generated from various combinations of a) Pd(OAc)₂ and (R)‐ 1 or (S)‐ 2 (1 : 2), b) (S)‐ 5 or (S)‐ 6 and (R)‐ 1 or (S)‐ 2 (1 : 2), or c) (i‐Bu)₂AlH with the preceding recipes. These factors effect the Heck arylation of 2,3‐dihydrofuran with phenyl trifluoromethylsulfonate. In contrast to analogous reactions with (R)‐binap (=(R)‐2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthalene), the major product 2‐phenyl‐2,3‐dihydrofuran is nearly racemic (≤12% ee).     

Homochiral Cobalt Phosphonates Containing Δ‐Type Chains with a Tunable Interlayer Distance and a Field‐Induced Phase Transition

Two pairs of enantiomeric Co^II compounds with formulas [Co₂(μ₃‐OH)(cyamp)(C_nH_2n+1COO)] (cyampH₂=(S)‐ or (R)‐[(1‐cyclohexylethyl)amino]methylphosphonic acid; n=1 ( 1 ); n=7 ( 2 )) were synthesized. The structures of S‐ 1 and S‐ 2 were determined by single‐crystal structural analyses. Both crystallize in a monoclinic chiral space group P2₁, and exhibit layered structures in which the Δ‐type chains of corner‐sharing Co₃(μ₃‐OH) triangles are connected by the phosphonate groups. The interlayer spaces are filled with the organic groups of the phosphonate and carboxylate ligands. Therefore, the distances between the layers can be manipulated by the length of the alkyl chain of the carboxylate ligands, from 14.6 Å in 1 to 20.0 Å in 2 . Magnetic studies were carried out for compounds S‐ 1 and S‐ 2 . Both show metamagnetism at low temperature. The critical field decreases with increasing interlayer distance from 8.18 kOe for S‐ 1 to 7.01 kOe for S‐ 2 at 1.8 K. The optical properties were also studied.     

O→S Relay Deprotection: A General Approach to Controllable Donors of Reactive Sulfur Species

Reactive sulfur species (RSS) are biologically important molecules. Among them, H₂S, hydrogen polysulfides (H₂S_n, n>1), persulfides (RSSH), and HSNO are believed to play regulatory roles in sulfur‐related redox biology. However, these molecules are unstable and difficult to handle. Having access to their reliable and controllable precursors (or donors) is the prerequisite for the study of these sulfur species. Reported in this work is the preparation and evaluation of a series of O‐silyl‐mercaptan‐based sulfur‐containing molecules which undergo pH‐ or F^?‐mediated desilylation to release the corresponding H₂S, H₂S_n, RSSH, and HSNO in a controlled fashion. This O→S relay deprotection serves as a general strategy for the design of pH‐ or F^?‐triggered RSS donors. Moreover, we have demonstrated that the O‐silyl groups in the donors could be changed into other protecting groups like esters. This work should allow the development of RSS donors with other activation mechanisms (such as esterase‐activated donors).     

Assemblies of 1D and 2D Copper(II) Chiral Coordination Polymers by Salicylaldehyde Schiff Bases: Synthesis,Crystal Structures,and Magnetic Properties

Reaction of CuCl₂ · 2H₂O with chiral Schiff bases and sodium dicyanamide led to the formation of two chiral copper(II) coordination polymers, namely [Cu₄(L¹)₂(dca)₄]_n ( 1 ) and [Cu₂(L²)(μ‐Cl)(dca)(H₂O)]_n · nH₂O ( 2 ) {H₂L¹ = (1R, 3S)‐N′,N′′‐bis[salicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, H₂L² = (1R, 3S)‐N′,N′′‐bis[3‐ethoxysalicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, dca = dicyanamide}. Both complexes were structurally characterized by elemental analyses, IR spectroscopy and single‐crystal X‐ray diffraction. Complex 1 exhibits a two‐dimensional polymeric structure formed by single dca bridging tetranuclear Cu₄ units. Complex 2 displays a left‐handed helical chain structure constructed from Cu₂ dimers with single dca bridges. The chirality of 1 and 2 was confirmed by circular dichroism (CD) measurements in solution. Both complexes exhibit strong antiferromagnetic couplings with J = –308(4) cm^–1 for 1 and J = –123(1) cm^–1 for 2 in 2–300 K.     

Synthesis and Characterization of Poly(chiral methylpropargyl ester)s Carrying Azobenzene Moieties

Novel chiral methylpropargyl esters bearing azobenzene groups, namely, 4‐[4′‐(benzyloxy)phenylazophenyl]‐ carbonyl‐(S)‐1‐methylpropargyl ester ( e ), 4‐[4′‐(n‐butyloxy)phenylazophenyl]carbonyl‐(S)‐1‐methylpropargyl ester ( f ), 4‐[4′‐(n‐hexyloxy)phenylazophenyl]carbonyl‐(S)‐1‐methylpropargyl ester ( g ), and 4‐[4′‐(n‐octyloxy)phenylazo‐ phenyl]carbonyl‐(S)‐1‐methylpropargyl ester ( h ) were synthesized and polymerized with Rh⁺(nbd)[η⁶‐C₆H₅B^?‐ (C₆H₅)₃] (nbd=norbornadiene) catalyst to give the corresponding polymers with moderate molecular weights (M_n=8.4×10³–15.7×10³) in good yields (76%? –?91%). The structures of polymers were illustrated by IR and NMR spectroscopies. Polymers were soluble in comment organic solvents including toluene, CHCl₃ CH₂Cl₂, THF, and DMSO, while insoluble in diethyl ether, n‐hexane and methanol. Large optical rotations of polymer solutions demonstrated that all the polymers take a helical structure with a predominantly one‐handed screw sense in organic solvents.     

The conformations of two copper(I) complexes of 1H‐benzimidazole‐2(3H)‐thione and thiosaccharinate

(Acetonitrile‐1κN)[μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S][1H‐benzimidazole‐2(3H)‐thione‐2κS]bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₂(CH₃CN)] or [Cu₂(tsac)₂(Sbim)₂(CH₃CN)] [tsac is thiosaccharinate and Sbim is 1H‐benzimidazole‐2(3H)‐thione], (I), is a new copper(I) compound that consists of a triply bridged dinuclear Cu—Cu unit. In the complex molecule, two tsac anions and one neutral Sbim ligand bind the metals. One anion bridges via the endocyclic N and exocyclic S atoms (μ‐S:N). The other anion and one of the mercaptobenzimidazole molecules bridge the metals through their exocyclic S atoms (μ‐S:S). The second Sbim ligand coordinates in a monodentate fashion (κS) to one Cu atom, while an acetonitrile molecule coordinates to the other Cu atom. The Cu^I—Cu^I distance [2.6286 (6) Å] can be considered a strong `cuprophilic' interaction. In the case of [μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S]bis[1H‐benzimidazole‐2(3H)‐thione]‐1κS;2κS‐bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₃] or [Cu₂(tsac)₂(Sbim)₃], (II), the acetonitrile molecule is substituted by an additional Sbim ligand, which binds one Cu atom via the exocylic S atom. In this case, the Cu^I—Cu^I distance is 2.6068 (11) Å.     

Structures,Energies, and Fundamental Vibrations of the Sulfonium Ions H3Sn+ (n = 1–4)

Using ab initio MO calculations at the MP2/6‐311G(2df,2pd) level of theory the most stable structures of the following seven ions were determined: H₃S⁺ (C_3v), H₂S–SH⁺ (C_s), H₂S–S–SH⁺ (C₁), HS–S(H)–SH⁺ (C₁), H₂S–S–S–SH⁺ (C₁), HS–S(H)–S–SH⁺ (C₁) and S(SH)₃⁺ (C₃). In the case of the isomeric H₃S₃⁺ cations the species protonated at the terminal sulfur atom is most stable while in the case of the H₃S₄⁺ ions the protonation at the β sulfur atom is energetically preferred. However, the energy differences between isomeric cations are rather small. At the same level of theory the wavenumbers of the harmonic fundamental vibrations were calculated and compared to the available experimental data leading to a support for the existing assignments in certain cases but in some cases to revisions. The reaction enthalpies and Gibbs free energies of the proton transfer reactions H₂S_n + H₂S_n+1 → H₃S_n⁺ + HS_n+1^– were calculated by the G2 method. For n = 1–3 the enthalpies are found in the range 639–731 kJ mol^–1.     

Novel pseudopolymorph of the active metabolite of perindopril

The dimethyl sulfoxide hemisolvate of perindoprilat [systematic name: (1S)‐2‐((S)‐{1‐[(2S,3aS,7aS)‐2‐carboxyoctahydro‐1H‐indol‐1‐yl]‐1‐oxopropan‐2‐yl}azaniumyl)pentanoate dimethyl sulfoxide hemisolvate], C₁₇H₂₈N₂O₅·0.5C₂H₆OS, an active metabolite of perindopril, has been synthesized, structurally characterized by single‐crystal X‐ray diffraction and compared with its ethanol disolvate analogue [Pascard et al. (1991). J. Med. Chem. 34 , 663–669]. Both compounds crystallize in the orthorhombic P2₁2₁2₁ space group in the same zwitterionic form, with a protonated alanine N atom and an anionic carboxylate group at the n‐alkyl chain. The three structural units present in the unit cell (two zwitterions and the solvent molecule) are held together by a rich system of O—H...O, N—H...O and C—H...O hydrogen‐bond contacts.     

Perindoprilat monohydrate

The title compound [systematic name: (1S)‐2‐((S)‐{1‐[(2S,3aS,7aS)‐2‐carboxyoctahydro‐1H‐indol‐1‐yl]‐1‐oxopropan‐2‐yl}azaniumyl)pentanoate monohydrate], C₁₇H₂₈N₂O₅·H₂O, (I)·H₂O, the active metabolite of the antihypertensive and cardiovascular drug perindopril, was obtained during polymorphism screening of perindoprilat. It crystallizes in the chiral orthorhombic space group P2₁2₁2₁, the same as the previously reported ethanol disolvate [Pascard, Guilhem, Vincent, Remond, Portevin & Laubie (1991). J. Med. Chem. 34 , 663–669] and dimethyl sulfoxide hemisolvate [Bojarska, Maniukiewicz, Sieroń, Fruziński, Kopczacki, Walczyński & Remko (2012). Acta Cryst. C 68 , o341–o343]. The asymmetric unit of (I)·H₂O contains one independent perindoprilat zwitterion and one water molecule. These interact via strong hydrogen bonds to give a cyclic R²₂(7) synthon, which provides a rigid molecular conformation. The geometric parameters of all three forms are similar. The conformations of the perhydroindole group are almost identical, but the n‐alkyl chain has conformational freedom. A three‐dimensional hydrogen‐bonding network of O—H...O and N—H...O interactions is observed in the crystal structure of (I)·H₂O, similar to the other two solvates, but because of the presence of different solvents the three crystal structures have diverse packing motifs. All three solvatomorphs are additionally stabilized by nonclassical weak C—H...O contacts.