The bis(ethylenedithio)tetrathiafulvalene‐based ionic charge‐transfer complex with 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone

In the ionic charge‐transfer (CT) complex composed of bis(ethylenedithio)tetrathiafulvalene (ET) and 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ), C₁₀H₈S₈·C₈Cl₂N₂O₂, the donor and acceptor molecules both form centrosymmetric dimers associated by strong face‐to‐face π–π interactions. The disordered DDQ molecules form a one‐dimensional π‐stacked column, while the ET molecules form a two‐leg ladder through additional short S...S contacts between adjacent π–π‐bonded dimers. The crystal structure of ET–DDQ revealed in this study will provide a valuable example of the two‐leg spin ladder system, which has rarely been reported for ET‐based CT complexes.     

(12,17‐Diethoxy­carbonyl‐2,3,6,­7,11,­18‐hexa­methyl­corrphy­cenato‐­κ4N)iodoiron(III) chloro­form solvate

The title complex, (diethyl 3,4,8,15,19,20‐hexa­methyl‐21,22,23,24‐tetraazopenta­cyclo­[16.2.1.1^2,5.1^7,11.1^14,17]­tetracosa‐1(20),2(22),3,5,7,9,11,13(24),14,16,18‐undecaene‐9,14‐dicarb­oxyl­ate‐κ⁴N)­iodo­iron(III) chloro­form solvate, [Fe(C₃₂H₃₂­N₄O₄)I]·­CHCl₃, shows an almost planar arrangement of the corrphycene moiety with a slightly distorted trapezoid pyramidal core; the Fe^III atom is 0.416 (1) Å from the plane of the C₂₀N₄ system. The Fe—N distances are 2.049 (3), 2.044 (3), 2.079 (3) and 2.075 (3) Å. The solvated chloro­form forms a C—H?O hydrogen bond [C?O 3.107 (10) Å] to an adjacent carbonyl O atom. This is the first X‐ray structure analysis of a corrphycenatoiron(III) derivative.     

Functional carbo‐Butadienes: Nonaromatic Conjugation Effects through a 14‐Carbon, 24‐π‐Electron Backbone

A systematic study of carbo‐butadiene motifs not embedded in an aromatic carbo‐benzene ring is described. Dibutatrienylacetylene (DBA) targets R¹?C(R)?C?C?C(Ph)?C≡C?C(Ph)?C?C?C(R)?R² are devised, in which R is C≡CSiiPr₃ and R¹ and R² are R, H, or 4‐X‐C₆H₄, with the latter including three known representatives (X: H, NMe₂, or NH₂). The synthesis method is based on the SnCl₂‐mediated reduction of pentaynediols prepared by early or late divergent strategies; the latter allows access to a OMe–NO₂ push–pull diaryl‐DBA. If R¹ and R² are H, an over‐reduced dialkynylbutatriene (DAB) with two allenyl caps was isolated instead of the unsubstituted DBA. If R¹=R²=R, the tetraalkynyl‐DBA target was obtained, along with an over‐reduced DBA product with a 12‐membered 1,2‐alkylidene‐1H₂,2H₂‐carbo‐cyclobutadiene ring. X‐ray crystallography shows that all of the acyclic DBAs adopt a planar trans–transoid–trans configuration. The maximum UV/Vis absorption wavelength is found to vary consistently with the overall π‐conjugation extent and, more intriguingly, with the π‐donor character of the aryl X substituents, which varies consistently with the first (reversible) reduction potential and first (irreversible) oxidation peak, as determined by voltammetry.     

Structures and Dynamic Solution Behavior of Cationic,Two‐Coordinate Gold(I)–π‐Allene Complexes

A family of seven cationic gold complexes that contain both an alkyl substituted π‐allene ligand and an electron‐rich, sterically hindered supporting ligand was isolated in >90 % yield and characterized by spectroscopy and, in three cases, by X‐ray crystallography. Solution‐phase and solid‐state analysis of these complexes established preferential binding of gold to the less substituted C?C bond of the allene and to the allene π face trans to the substituent on the uncomplexed allenyl C?C bond. Kinetic analysis of intermolecular allene exchange established two‐term rate laws of the form rate=k₁[complex]+k₂[complex][allene] consistent with allene‐independent and allene‐dependent exchange pathways with energy barriers of ΔG^≠₁=17.4–18.8 and ΔG^≠₂=15.2–17.6 kcal mol^?1, respectively. Variable temperature (VT) NMR analysis revealed fluxional behavior consistent with facile (ΔG^≠=8.9–11.4 kcal mol^?1) intramolecular exchange of the allene π faces through η¹‐allene transition states and/or intermediates that retain a staggered arrangement of the allene substituents. VT NMR/spin saturation transfer analysis of [{P(tBu)₂o‐binaphthyl}Au(η²‐4,5‐nonadiene) ]⁺SbF₆^? ( 5 ), which contains elements of chirality in both the phosphine and allene ligands, revealed no epimerization of the allene ligand below the threshold for intermolecular allene exchange (ΔG^≠_298K=17.4 kcal mol^?1), which ruled out the participation of a η¹‐allylic cation species in the low‐energy π‐face exchange process for this complex.     

All‐Metal Antiaromaticity in Sb4‐Type Lanthanocene Anions

Antiaromaticity, as introduced in 1965, usually refers to monocyclic systems with 4n π electrons. This concept was extended to all‐metal molecules after the observation of Li₃Al₄^? in the gas phase. However, the solid‐phase counterparts have not been documented to date. Herein, we describe a series of all‐metal antiaromatic anions, [Ln(η⁴‐Sb₄)₃]^3?(Ln=La, Y, Ho, Er, Lu), which were isolated as the K([2.2.2]crypt) salts and identified by single‐crystal X‐ray diffraction. Based on the results obtained from the chemical bonding analysis, multicenter indices, and the electron‐counting rule, we conclude that the core [Ln(η⁴‐Sb₄)₃]^3? fragment of the crystal has three locally π‐antiaromatic Sb₄ fragments. This complex represents the first locally π‐antiaromatic all‐metal system in the solid state, which is stabilized by interactions of the three π‐antiaromatic units with the central metal atom.     

Bis­(acesulfamato)­tetra­aqua­cobalt(II)

The crystal structure of the first acesulfame–metal complex, namely tetra­aqua­bis­[6‐methyl‐1,2,3‐oxa­thia­zin‐4(3H)‐onato 2,2‐dioxide‐κN]­cobalt(II), [Co(C₄H₄NO₄S)₂(H₂O)₄], is re­ported. The Co^II ion resides on a twofold axis and is coordinated by four aqua ligands defining the basal plane and by two monodentate acesulfamate ligands, via their ring N atoms, in the axial positions. Two intra‐ and three intermolecular hydrogen‐bonding interactions stabilize the crystal structure and form an infinite three‐dimensional lattice.     

{3,3′‐[2,2′‐(Ethylenedioxy)dibenzyl­idene]bis(S‐methyl dithiocarbazate)}­nickel(II)

The tetradentate N₂S₂ Schiff base ligand 3,3′‐[2,2′‐(ethyl­ene­di­oxy)di­benzyl­idene]­bis­(S‐methyl di­thio­car­ba­zate) (H₂L), prepared by the condensation of S‐methyl di­thio­carb­aza­te with 1,4‐bis(2‐formyl­phenyl)‐1,4‐dioxa­butane in a 1:2 molar ratio, reacts with nickel acetate to form the title neutral metal complex, [Ni(C₂₀H₂₀N₄O₂S₄)]. The X‐ray structure of the complex shows a distorted square‐planar geometry around the Ni atom. The monomeric units are weakly associated into dimers via a long Ni?S interaction [3.569 (1) Å]. These dimeric units are then linked by C—H?S intermolecular contacts to form a polymeric chain along the a axis.     

Synthesis, π‐Face‐Selective Aggregation,and π‐Face Chiral Recognition of Configurationally Stable C3‐Symmetric Propeller‐Chiral Molecules with a π‐Core

The C₃‐symmetric propeller‐chiral compounds (P,P,P)‐ 1 and (M,M,M)‐ 1 with planar π‐cores perpendicular to the C₃‐axis were synthesized in optically pure states. (P,P,P)‐ 1 possesses two distinguishable propeller‐chiral π‐faces with rims of different heights named the (P/L)‐face and (P/H)‐face. Each face is configurationally stable because of the rigid structure of the helicenes contained in the π‐core. (P,P,P)‐ 1 formed dimeric aggregates in organic solutions as indicated by the results of ¹H NMR, CD, and UV/Vis spectroscopy and vapor pressure osmometry analyses. The (P/L)/(P/L) interactions were observed in the solid state by single‐crystal X‐ray analysis, and they were also predominant over the (P/H)/(P/H) and (P/L)/(P/H) interactions in solution, as indicated by the results of ¹H and 2D NMR spectroscopy analyses. The dimerization constant was obtained for a racemic mixture, which showed that the heterochiral (P,P,P)‐ 1 /(M,M,M)‐ 1 interactions were much weaker than the homochiral (P,P,P)‐ 1 /(P,P,P)‐ 1 interactions. The results indicated that the propeller‐chiral (P/L)‐face interacts with the (P/L)‐face more strongly than with the (P/H)‐face, (M/L)‐face, and (M/H)‐face. The study showed the π‐face‐selective aggregation and π‐face chiral recognition of the configurationally stable propeller‐chiral molecules.     

trans‐[N,N′‐Bis­(salicyl­idene)­cyclo­hexane‐1,2‐diaminato]­nickel(II)–chloro­form (1/1)

In the title complex, trans‐{2,2′‐[cyclo­hexane‐1,2‐diyl­bis­(ni­t­rilo­methyl­idyne)]­di­phenol­ato‐κ⁴O,N,N′,O′}­nickel(II)–chloro­form (1/1), [Ni(C₂₀H₂₀N₂O₂)]·CHCl₃, the Ni atom has a square‐planar geometry, slightly tetrahedrally distorted. The Ni—N and Ni—O bonding distances are within the expected ranges for Ni–Schiff base derivatives. The di­imine bridge has a gauche conformation with the cyclo­hexyl ring almost coplanar with the NiN₂O₂ plane. The complex mol­ecules pack in dimers with an Ni?Ni distance of 3.59 (1) Å and form a three‐dimensional structure displaying a herring‐bone configuration. Channels are occupied by solvent mol­ecules, which are involved in C—H?O hydrogen bonds with the ligand O atoms.     

Enhanced Reactivities of Iron(IV)‐Oxo Porphyrin π‐Cation Radicals in Oxygenation Reactions by Electron‐Donating Axial Ligands

The proximal axial ligand in heme iron enzymes plays an important role in tuning the reactivities of iron(IV)‐oxo porphyrin π‐cation radicals in oxidation reactions. The present study reports the effects of axial ligands in olefin epoxidation, aromatic hydroxylation, alcohol oxidation, and alkane hydroxylation, by [(tmp)^+. Fe^IV(O)(p‐Y‐PyO)]⁺ ( 1 ‐Y) (tmp=meso‐tetramesitylporphyrin, p‐Y‐PyO=para‐substituted pyridine N‐oxides, and Y=OCH₃, CH₃, H, Cl). In all of the oxidation reactions, the reactivities of 1 ‐Y are found to follow the order 1 ‐OCH₃ > 1 ‐CH₃ > 1 ‐H > 1 ‐Cl; negative Hammett ρ values of ?1.4 to ?2.7 were obtained by plotting the reaction rates against the σ_p values of the substituents of p‐Y‐PyO. These results, as well as previous ones on the effect of anionic nucleophiles, show that iron(IV)‐oxo porphyrin π‐cation radicals bearing electron‐donating axial ligands are more reactive in oxo‐transfer and hydrogen‐atom abstraction reactions. These results are counterintuitive since iron(IV)‐oxo porphyrin π‐cation radicals are electrophilic species. Theoretical calculations of anionic and neutral ligands reproduced the counterintuitive experimental findings and elucidated the root cause of the axial ligand effects. Thus, in the case of anionic ligands, as the ligand becomes a better electron donor, it strengthens the FeO? H bond and thereby enhances its H‐abstraction activity. In addition, it weakens the Fe?O bond and encourages oxo‐transfer reactivity. Both are Bell–Evans–Polanyi effects, however, in a series of neutral ligands like p‐Y‐PyO, there is a relatively weak trend that appears to originate in two‐state reactivity (TSR). This combination of experiment and theory enabled us to elucidate the factors that control the reactivity patterns of iron(IV)‐oxo porphyrin π‐cation radicals in oxidation reactions and to resolve an enigmatic and fundamental problem.     

Induced‐Fit Binding of π‐Electron‐Donor Substrates to Macrocyclic Aromatic Ether Imide Sulfones: A Versatile Approach to Molecular Assembly

Novel macrocyclic receptors that bind electron‐donor aromatic substrates through π‐stacking donor–acceptor interactions are obtained by cycloimidisation of an amine‐functionalised aryl ether sulfone with pyromellitic and 1,4,5,8‐naphthalenetetracarboxylic dianhydrides. These macrocycles can form complexes with a wide variety of π‐donor substrates, including tetrathiafulvalene, naphthalene, anthracene, pyrene, perylene and functional derivatives of these polycyclic hydrocarbons. The resulting supramolecular assemblies range from simple 1:1 complexes to [2]‐ and [3]pseudorotaxanes and even (as a result of crystallographic disorder) an apparent polyrotaxane. Direct five‐component self‐assembly of a metal‐centred [3]pseudorotaxane is also observed on complexation of a macrocyclic ether imide with 8‐hydroxyquinoline in the presence of palladium(II) ions. Binding studies in solution were carried out by using ¹H NMR and UV/Vis spectroscopy, and the stoichiometries of binding were confirmed by Job plots based on the charge‐transfer absorption bands. The highest association constants were found for strong π‐donor guests with large surface areas, notably perylene and 1‐hydroxypyrene, for which K_a values of 1.4×10³ and 2.3×10³ M ^?1, respectively, were found. Single‐crystal X‐ray analyses of the receptors and their derived complexes reveal large induced‐fit distortions of the macrocyclic frameworks as a result of complexation. These structures provide compelling evidence for the existence of strong attractive forces between the electronically complementary aromatic π systems of host and guest.     

Bis­[S‐methyl 3‐(2‐bromo­benzyl­idene)­di­thio­cab­aza­to‐N3,S]­platinum(II)

The Schiff base ligand in the title complex, [Pt(C₉H₈BrN₂S₂)₂], is deprotonated from its tautomeric thiol form and coordinated to Pt^IIvia the mercapto S and β–N atoms. The configuration about Pt^II is a perfect square‐planar, with two equivalent Pt—N [2.023 (3) Å] and Pt—S [2.293 (1) Å] bonds. The phenyl ring is twisted against the coordination moiety Pt1/N1/N1′/S2′/S2 by 31.8 (2)°, due to the steric hindrance induced by ortho‐substituted bulky Br atom.     

Two hydro­chlorides of 7‐methyl‐3,7,11,17‐tetra­aza­bi­cyclo­[11.3.1]­heptadeca‐1(17),13,15‐triene

The X‐ray structure determinations of the two title com­pounds, namely 7‐methyl‐7,17‐di­aza‐3,11‐diazo­niabi­cyclo[11.3.1]­hep­ta­deca‐1(17),13,15‐triene dichloride monohydrate, C₁₄H₂₆N₄²⁺·2Cl^?·H₂O, (I), and 7‐methyl‐17‐aza‐3,7,11‐triazo­niabi­cyclo­[11.3.1]­heptadeca‐1(17),13,15‐triene 2.826‐chloride 0.174‐nitrate, C₁₄H₂₇N₄³⁺·2.826Cl^?·0.174NO₃^?, (II), are re­ported. Protonation occurs at the secondary amine N atoms in (I) and at all three amine N atoms in (II) to which the Cl^? ions are linked via N—H?Cl hydrogen bonds. The macrocyclic hole is quite different in both structures, as is observed by comparing particularly the N3?N4 distances [2.976 (4) and 4.175 (4) Å for (I) and (II), respectively]. In (II), a Cl^? ion alternates with an NO₃^? ion in a disordered structure.     

catena‐Poly­[bis­[(2,2‐bi­pyridine‐κ2N,N′)­copper(II)]‐μ4‐1,2,4,5‐benzene­tetra­carboxyl­ato‐κ4O1:O2:O3:O4]

In the title complex, [Cu₂(C₁₀H₂O₈)(C₁₀H₈N₂)₂]_n, the Cu^II cation has a four‐coordinated environment, completed by two carboxyl O atoms belonging to two 1,2,4,5‐benzene­tetra­carboxyl­ate anions (TCB⁴⁻) and two N atoms from one 2,2′‐bi­pyridine (2,2′‐bipy) ligand, forming a distorted square‐planar geometry. The [Cu(2,2′‐bipy)]²⁺ moieties are bridged by TCB⁴⁻ anions, which lie about inversion centres, forming an infinite one‐dimensional coordination polymer with a double‐chain structure along the a axis. A two‐dimensional network structure is formed via a face‐to‐face π–π interaction between the 2,2′‐bipy rings belonging to two adjacent double chains, at a distance of approximately 3.56 Å.     

Bis[1‐(pyridin‐2‐yl)­ethano­ne‐κN 4‐phenyl­thio­semicarbazonato‐κ2N4,S]­manganese(II)

One half of the mol­ecule of the title complex, [Mn(C₁₄H₁₃N₄S)₂], is related to the other half by a twofold axis passing through the Mn atom. This high‐spin Mn atom is six‐coordinated, in an octahedral geometry, by the azomethine N, the pyridyl N and the thiol­ate S atom of two planar 1‐­(pyridin‐2‐yl)­ethanone N(4)‐phenyl­thio­semicarbazone lig­ands. In the crystal, the mol­ecules are interconnected by N—­H?S and C—H?N interactions, forming a three‐dimensional network.     

A Series of Isolable Silanoic Thio‐, Seleno‐, and Telluroesters (LSi(X)OR) with Donor‐Supported SiX Double Bonds (L=β‐Diketiminate; X=S,Se, Te)

The first silicon analogues of carbonic (carboxylic) esters, the silanoic thio‐, seleno‐, and tellurosilylesters 3 (Si?S), 4 (Si?Se), and 5 (Si?Te), were prepared and isolated in crystalline form in high yield. These thermally robust compounds are easily accessible by direct reaction of the stable siloxysilylene L(Si:)OSi(H)L′ 2 (L=HC(CMe)₂[N(aryl)₂], L′=CH[(C?CH₂)‐CMe][N(aryl)]₂; aryl=2,6‐iPr₂C₆H₃) with the respective elemental chalcogen. The novel compounds were fully characterized by methods including multinuclear NMR spectroscopy and single‐crystal X‐ray diffraction analysis. Owing to intramolecular N→Si donor–acceptor support of the Si?X moieties (X=S, Se, Te), these compounds have a classical valence‐bond N⁺–Si–X^? resonance betaine structure. At the same time, they also display a relatively strong nonclassical Si?X π‐bonding interaction between the chalcogen lone‐pair electrons (n_π donor orbitals) and two antibonding Si? N orbitals (σ*_π acceptor orbitals mainly located at silicon), which was shown by IR and UV/Vis spectroscopy. Accordingly, the Si?X bonds in the chalcogenoesters are 7.4 ( 3 ), 6.7 ( 4 ), and 6.9 % ( 5 ) shorter than the corresponding Si? X single bonds and, thus, only a little longer than those in electronically less disturbed Si?X systems (“heavier” ketones).     

Ferromagnetic Interactions in a 1D Alternating Linear Chain of π‐Stacked 1,3‐Diphenyl‐7‐(thien‐2‐yl)‐1,4‐dihydro‐1,2,4‐benzotriazin‐4‐yl Radicals

X‐ray studies show that 1,3‐diphenyl‐7‐(thien‐2‐yl)‐1,4‐dihydro‐1,2,4‐benzotriazin‐4‐yl ( 6 ) adopts a distorted, slipped π‐stacked structure of centrosymmetric dimers with alternate short and long interplanar distances (3.48 and 3.52 Å). Cyclic voltammograms of 7‐(thien‐2‐yl)benzotriazin‐4‐yl 6 show two fully reversible waves that correspond to the ?1/0 and 0/+1 processes. EPR and DFT studies on radical 6 indicate that the spin density is mainly delocalized over the triazinyl fragment. Magnetic susceptibility measurements show that radical 6 obeys Curie–Weiss behavior in the 5–300 K region with C=0.378 emu K mol^?1 and θ=+4.72 K, which is consistent with ferromagnetic interactions between S=1/2 radicals. Fitting the magnetic susceptibility revealed the behavior is consistent with an alternating ferromagnetic chain (g=2.0071, J₁=+7.12 cm^?1, J₂=+1.28 cm^?1).     

2,8‐Di­hydroxy‐1,3,7,9‐tetra­methyl‐6,12‐di­hydro­dipyrido­[1,2‐a:1′,2′‐d]pyrazine­diyl­ium dichloride dihydrate

The 2,8‐di­hydroxy‐1,3,7,9‐tetra­methyl‐6,12‐di­hydro­di­pyrido[1,2‐a:1′,2′‐d]pyrazine­diyl­ium dication possesses 2/m symmetry and lies in the mirror plane together with a chloride anion and the water O atom. The dication also lies on an inversion centre, i.e. C₁₆H₂₀N₂O₂²⁺·2Cl^?·2H₂O. Due to these symmetry constrictions the dication adopts an unexpected planar conformation. Molecules are linked by O—H?O and O—H?Cl hydrogen bonds to form chains, which are cross‐connected by C—H?Cl attractive interactions forming a complex three‐dimensional hydrogen‐bond network.     

2,2′‐[2,3‐Di­hydro‐2‐(prop‐2‐enyl)‐1H‐isoindole‐1,3‐diyl­idene]bis(propane­di­nitrile)–tetra­thia­fulvalene (1/1), TCPI–TTF

The title complex, C₁₇H₉N₅·C₆H₄S₄, contains π‐deficient bis(di­nitrile) and TTF mol­ecules stacked alternately in columns along the a‐axis direction; the interplanar angle between the TTF molecule and the isoindolinyl C₄N[C(CN)₂]₂ moiety is 1.21 (4)°. The N‐allyl moiety in the TCPI mol­ecule is oriented at an angle of 87.10 (10)° with respect to the five‐membered C₄N ring, and the four C[triple‐bond]N bond lengths range from 1.134 (3) to 1.142 (3) Å, with C—C[triple‐bond]N angles in the range 174.3 (3)–176.9 (2)°. In the TTF system, the S—C bond lengths are 1.726 (3)–1.740 (3) and 1.751 (2)–1.763 (2) Å for the external S—C(H) and internal S—C(S) bonds, respectively.     

Bis­(di‐μ‐acetato‐aqua{2‐[N‐ethyl‐N‐(2‐hydroxy‐4‐methyl­benzyl)­amino­methyl]‐1‐methyl­benz­imid­az­ole}­nickel)­nickel(II) tetra­hy­drate

The previously unknown title compound, tetra‐μ‐ace­tato‐1:2κ²O;1:2κ²O:O′;­2:3κ²O;­2:3κ²O:O′‐di­aqua‐1κO,3κO‐bis­(μ‐2‐{[N‐ethyl‐N‐(2‐hy­droxy‐5‐methylbenzyl)­am­ino]­methyl}‐1‐methyl‐1H‐benz­imid­az­ole)‐1κ³N³,N,O:2κO;3κ³N³,N,O:2κO‐tri­nickel(II) tetra­hy­drate, [Ni₃(C₁₈H₂₂N₃O)₂(C₂H₃O₂)₄(H₂O)₂]·­4H₂O, (I), is a centrosymmetric linear trinuclear nickel(II) complex, where the Ni atoms are in an octahedral coordination and the ligand heteroatoms act so as to model amino acid residues.