Solid-State Photoswitching of Hydrazones Based on Excited-State Intramolecular Proton Transfer.

The development of new photochromic systems is motivated by the possibility of controlling the properties and functions of materials with high spatial and temporal resolution in a reversible manner. While there are several classes of photoswitches operating in solution, the design of systems efficiently operating in the solid state remains highly challenging, mainly due to limitations related to confinement effects. Triaryl-hydrazones represent a relatively new subclass of bistable hydrazone photoswitches exhibiting efficient / photochromism in solution.

Cationic -Tricarbollide μ-10,11-H-10,11-H-7-MeN--7,8,9-CBH and Its Halogenated Derivatives: The Slow Iodination Process Occurring through Cationic Iodonium Tricarbollides.

A series of -tricarbollides based on 10,11-X-7-MeN--7,8,9-CBH (X = H, Cl, Br, I) and their protonated, i.e. cationic, counterparts, which have an extra H-bridge over the B10-B11 vector in the open pentagonal belt, were prepared.

Single Step Synthesis of Non-symmetric Azoarenes Using Buchwald-Hartwig Amination.

Aromatic azo compounds stand as a highly sought-after class of substances owing to their extensive array of applications across various fields. Despite their significance, their synthesis often presents challenges, requiring either multistep reactions or being restricted to specific substrate types. In this study, we are showing the universality and mechanistic aspects of a one-step approach for synthesis of nonsymmetrical azoarenes via the Buchwald-Hartwig amination reaction of (pseudo)haloaromatics with arylhydrazines, conducted in the presence of atmospheric oxygen.

Redox Cycling with Tellurium. Si-H Bond Activation by a Lewis Superacidic Tellurenyl Cation.

The C,N-chelated aryltellurenyl triflate [2-(tBuNCH)CHTe][OTf] (1) activates the Si-H bonds in the tertiary silanes RSiH via umpolung of H to H to give rise to the iminium salts (tBuN(H)CH)CHTeSiR][OTf] (2, R=Et, Ph (elusive) and R=Si(CH) isolated; OTf=OSCF) comprising Te-Si bonds, which are capable of generating silyl triflates, RSiOTf, under attack of a second equivalent of 1. The unprecedented Si-H activation was utilized in main group redox catalysis using p-quinones, which were converted into (silylated) hydroquinones.

Antimony centre in three different roles: does donor strength or acceptor ability determine the bonding pattern?

A set of antimony(III) compounds containing a ligand (Ar) with a pendant guanidine function (where Ar = 2-[(MeN)CN]CH) was prepared and characterized. This includes triorgano-Ar3Sb, diorgano-Ar2SbCl and monoorgano-ArSbCl2 compounds and they were characterized by H and C NMR spectroscopy and by single-crystal X-ray diffraction analysis (sc-XRD). The coordination capability of Ar3Sb and Ar2SbCl was examined in the reactions with either -[PdCl(CHCN)] or PtCl and complexes -[(κ-Sb,N-Ar3Sb)MCl] (M = Pd 1, Pt 2) and [(κ-N,Sb,N-Ar2SbCl)MCl] (M = Pd 3, Pt 4) were isolated, while their structures were determined by sc-XRD.

Synthesis, photophysics and two-photon absorption of imidazole-centred tripodal chromophores.

Tripodal push-pull chromophores with D-(π-A) arrangement were synthesized using 1-methyl-2,4,5-triphenyl-1-imidazole as a central electron donor, and their thermal, electrochemical, photophysical and non-linear optical properties were studied and corroborated with quantum-chemical calculations. Their facile synthesis involved Suzuki-Miyaura and Knoevenagel reactions, allowing the installation of various peripheral electron acceptors such as formyl, cyano, ester, trifluoromethyl and more complex moieties such as malonic/acetic acid derivatives, indan-1,3-dione and rhodanine. All phenyl rings appended at the central imidazole core were more or less twisted depending on the peripheral substitution.

Exploring the impact of alignment media on RDC analysis of phosphorus-containing compounds: a molecular docking approach.

Residual dipolar couplings (RDCs) are employed in NMR analysis when conventional methods, such as -couplings and nuclear Overhauser effects (NOEs) fail. Low-energy (optimized) conformers are often used as input structures in RDC analysis programs. However, these low-energy structures do not necessarily resemble conformations found in anisotropic environments due to interactions with the alignment medium, especially if the analyte molecules are flexible.

B-substituted group 1 phosphides: synthesis and reactivity.

1-Boryl-8-phosphinonaphthalenes 1-BCy-8-PCl-CH (1) and 1-BCy-8-PPhCl-CH (2) were prepared and used as starting materials for the synthesis of B-substituted phosphides. The reduction of 1 and 2 by Mg provided neutral compounds [1-BCy-8-PCy-CH] (3) and [1-BCy-8-PPh-CH] (4). Compound 3 represents the dimer of phosphinoborane 1-BCy-8-PCy-CH while complex 4 is a rare example of a discrete B ← P coordinated diphosphine.

Direct Cyclopalladation of Fluorinated Benzyl Amines by Pd(OAc): The Coexistence of Multinuclear Pd Reaction Pathways Highlights the Importance of Pd Speciation in C-H Bond Activation.

Palladacycles are key intermediates in catalytic C-H bond functionalization reactions and important precatalysts for cross-couplings. It is commonly believed that palladacycle formation occurs through the reaction of a substrate bearing a C-H bond to a suitable metal-directing group for interaction with, typically, mononuclear "Pd(OAc)" species, with cyclopalladation liberating acetic acid as the side product. In this study, we show that ,-dimethyl-fluoro-benzyl amines, which can be cyclopalladated either or to fluorine affording two regioisomeric products, can occur by a direct reaction of Pd(OAc), proceeding via higher-order cyclopalladated intermediates.

Synthesis and reactivity of alkali metal aluminates bearing bis(organoamido)phosphane ligand.

In this study, we report a group of alkali metal aluminates bearing bis(organoamido)phosphane ligand. The starting complex {[PhP(NBu)]AlMe}Li·OEt (1) was prepared by stepwise deprotonation of the parent PhP(NHBu) by BuLi and AlMe. Further derivatization of aluminate 1 was performed by the virtual substitution of lithium -{[PhP(NBu)]AlMe}K (2), methyl substituents - {[PhP(NBu)]AlH}Li·THF (3), modification of steric bulk and induction effects on the phosphorus atom - {[BuP(-2,6-iPrCH)]AlMe}Li·(OEt) (4), and phosphorus atom oxidation state {[Ph(Y)P(NBu)]AlMe}Li (Y = O (5), S (6), Se (7), Te (8)).

Switchable cyclopalladation of substrates containing two directing groups: on the way to non-symmetrical [2.2]-dipalladaparacyclophanes.

Simple switching of the site-selectivity of C-H activation reactions of substrates containing multiple directing groups is particularly important for the so-called late stage functionalization synthetic approach. In this work, we verified the possibility of achieving this by adding acids of different strengths. Using a substrate containing two differently strong (and basic) directing groups, the influence of the addition of acids on the regioselectivity of the C-H activation step of the reaction with palladium acetate was thoroughly studied.

Carbazole-Fluorene Copolymers with Various Substituents at the Carbazole Nitrogen: Structure-Properties Relationship.

Carbazole derivatives, carbazole-containing polymers and iridium complexes are of interest due to many possible applications in photonics, electronics and biology, particularly as active or hole-transporting layers in organic as well as perovskite devices due to their interesting properties. Here, a series of carbazole-fluorene conjugated copolymers with various substituents at the -carbazole position (2-methoxycarbonylethyl, 2-carboxyethyl, 2-ethylhexyl, and nonan-2,4-dionatoiridium(III)bis(2-phenylpyridine-,)-9-yl) was prepared by Suzuki coupling. Their photophysical, electrochemical and electroluminescence (EL) properties were studied.

Can Copper(I) and Silver(I) be Hydrogen Bond Acceptors?

Gold(I) centers can form moderately strong (Au⋅⋅⋅H) hydrogen bonds with tertiary ammonium groups, as has been demonstrated in the 3AuCl (3 =1-(tert-butyl)-3-phenyl-4-(2-((dimethylammonio)methyl)phenyl)-1,2,4-triazol-5-ylidene) complex. However, similar hydrogen bonding interactions with isoelectronic silver(I) or copper(I) centers are unknown. Herein, we first explored whether the Au⋅⋅⋅H bond originally observed in 3AuCl can be strengthened by replacing Cl with Br or I.

Colour-tuneable solid-state fluorescence of crystalline powders formed from push-pull substituted 2,5-diphenyl-stilbenes.

The solid-state fluorescence (SSF) of eight DPA-DPS-EWG derivatives (DPA = diphenylamino, DPS = 2,5-diphenyl-stilbene building block, EWG = electron withdrawing group) was studied. Varying the strength of the EWG enabled the tuning of the LUMO energy within a range broader than 1 eV, while the simultaneous changes of HOMO energy were less than 0.1 eV, according to cyclic voltammetry.

The reactivity of antimony and bismuth ,,-pincer compounds toward K[BEtH] - the formation of heterocyclic compounds . element-element bonds stable terminal Sb-H bonds.

The oxidative addition of CFSOCHSi(CH) (NpOTf) toward organopnictogen(I) ,,-pincer compounds, [2,6-(DippNCH)CH]E (1-E, where E = Sb, Bi; Dipp = 2,6-iPrCH) produced compounds [2,6-(DippNCH)CH]E(Np)(OTf) (2-E, where E = Sb, Bi). By analogy, the reduction of [2,6-(MeNCH)CH]ECl (3-E, where E = Sb, Bi) followed by treatment with NpOTf or MeI gave compounds [2,6-(MeNCH)CH]E(R)(X) (R/X = Np/OTf 4-E, where E = Sb, Bi; R/X = Me/I 5-Sb). The reactivity of these compounds toward 1 eq.

Beyond simple hetero Diels-Alder cycloadditions. A new type of element-ligand cooperativity at N,C,N-coordinated arsinidene and stibinidene centres in the reaction with an electron-deficient alkyne.

The reactivity of two types of organopnictogen(I) N,C,N-pincer ligand coordinated compound, [2,6-(DippNCH)CH]E (1-E, where E = As, Sb, Bi; Dipp = 2,6-iPrCH) and [2-(DippNCH)-6-(DippNHCH)CH]E (6-E, where E = As or Sb), toward an electron-deficient alkyne, dimethyl acetylenedicarboxylate (DMAD), is reported. All reactions represent remarkable examples of element-ligand cooperation (ELC). In the first step, all compounds react dearomatization of a latent heteropnictole ring producing rare examples of hetero Diels-Alder (DA) adducts.

Reactivity of a N-Coordinated Germylene-Borane Complex: From Ge→B to Ge→Ga Coordination.

Reactivity studies of the Ge →B complex L(Cl)Ge⋅BH (1; L=2-Et NCH -4,6-tBu -C H ) were performed to determine the effect on the Ge →B donation. N-coordinated compounds L(OtBu)Ge⋅BH (2) and [LGe⋅BH ] (3) were prepared. The possible tuning of the Ge →B interaction was proved experimentally, yielding compounds 1-PPh -8-(LGe)-C H (4) and L(Cl)Ge⋅GaCl (5) without a Ge →B interaction.

Lithium, Magnesium, and Zinc Centers N,N'-Chelated by an Amine-Amide Hybrid Ligand.

The synthesis and structure of lithium, magnesium, and zinc complexes ,'-chelated by a hybrid amine-amido ligand ([2-(MeNCH)CHNR], abbreviated as LR, where R = H, SiMe, or Bn) are reported. The reaction of the least sterically demanding LH with various magnesium sources gives the hexameric imide [LMg] () by the elimination of -butane from LHMgBu () or by the reaction of LHLi () with MeMgBr. [LH]Mg () is obtained through the addition of 0.

Molecular Rearrangement of Pyrazino[2,3-]quinolin-5(6)-ones during Their Reaction with Isocyanic Acid.

New tetrahydropyrazino[2,3-]quinolin-5(6)-ones were prepared from 3-chloroquinoline-2,4(1,3)-diones and ethylene diamine. In their reaction with HNCO, an unprecedented molecular rearrangement produced new types of hydantoin derivatives. All prepared compounds were characterized on the basis of their H, C, and N NMR and ESI mass spectra and some were authenticated by X-ray analysis of single crystalline material.

Reversible addition of tin(II) amides to nitriles.

Lappert's stannylene (Sn[N(SiMe)]) has been reacted with various nitriles, dinitriles and trinitriles with the formation of heteroleptic amidotin(II) amidinates of the general formulae [RC(NSiMe)]SnN(SiMe), R'{[C(NSiMe)]SnN(SiMe)} and R''{[C(NSiMe)]SnN(SiMe)}, where R = Ph (1), 2-(CN)-CH (2), 3-(CN)-CH (3); R' = 1,3-CH (4), 1,4-CH (5) and R'' = 1,3,5-CH (6). The reactions of amidotin(II) benzamidinate 1 with an excess of benzonitrile proceed to homoleptic tin(II) bis(benzamidinate) [PhC(NSiMe)]Sn, which reversibly eliminates benzonitrile and 1 when warmed. The premise of reversibility has been supported by a multinuclear time-dependent NMR study and a theoretical (DFT) description.

Tetrazene-Characterization of Its Polymorphs.

The reinvestigation of tetrazene single crystalline material by means of X-ray methods resulted in a slightly different structure when compared to previously published data. Reaction conditions responsible for different crystalline modification formation were investigated. Newly described C form was found to be the primary reaction product and the combined action of temperature and the presence of water over time is required for the transition to the A form.

,-coordinated Ru cation: a robust catalyst for aerobic oxidations of benzylamine and benzyl alcohol.

A stable ionic κ,-coordinated Ru complex shows excellent catalytic activity in aerobic oxidations of benzylamine and benzyl alcohol. This complex is stabilized by a stannylene-phosphine -substituted naphthalene ligand, which can act as either a reducing agent for a Ru(III) complex or as a κ,-chelating ligand for Ru(II) compounds.