Search

Low‐cost molecular emitters that merge circularly polarized luminescence (CPL) and thermally activated delayed fluorescence (TADF) properties are attractive for many high‐tech applications. However, the design of such emitters remains a difficult task. To address this challenge, here, we propose a simple and efficient strategy, demonstrated by the design of pseudochiral‐at‐metal complexes [Cu(L*)DPEPhos]PF6 bearing a (+)/(−)‐menthol‐derived 1,10‐phenanthroline ligand (L*). These complexes exhibit a yellow CP‐TADF with a record‐high quantum yield (close to 100 %) and high dissymmetry factor (|glum|~1×10−2). Remarkably, the above compounds also show a negative thermal‐quenching (NTQ) of luminescence in the 300–77 K range. Exploiting the designed Cu(I) emitters, we fabricated efficient CP‐TADF OLEDs displaying mirror‐imaged CPL bands with high |gEL| factors of 1.5×10−2 and the maximum EQE of 6.15 %. Equally important, using the (+)‐[Cu(L*)DPEPhos]PF6 complex, we have discovered that an external magnetic field noticeably suppresses CP‐TADF of Cu(I) emitters. These findings are an important contribution to the CPL phenomenon and provide access to highly efficient, low‐cost and robust CP‐TADF emitters. [ABSTRACT FROM AUTHOR]

Herein we describe Pd‐catalyzed cross‐coupling reaction of α‐pinene derivative – pinacarvone O‐methyl oxime (1) with aryl halides (2). Surprisingly, the formation of the C−C coupling product was accompanied by an unexpected opening of the pinene bicyclic structure. The (Z)‐2‐aryl‐4,4,5‐trimethylcyclohexa‐2,5‐dien‐1‐one O‐methyl oxime (3) was formed as the resulting product. The reaction conditions of the developed synthetic procedure were carefully optimized and the reaction mechanism was supposed on the basis of data obtained by structural and computational methods. [ABSTRACT FROM AUTHOR]

Zinc(II) and cadmium(II) chlorido complexes with an N,N-chelating nopinane-annelated 4,5-diazafluoren-9-one ligand (LO) were synthesized. While the zinc(II) complex is mononuclear and adopts a tetrahedral ZnN2Cl2 coordination geometry, its cadmium(II) analogue features a 1D polymeric structure due to the bridging coordination of chlorido ligands with Cd2+ ions having an octahedral CdN2Cl4 coordination geometry. The photophysical properties of the oxygen-containing LO ligand and its zinc(II) and cadmium(II) complexes were studied in solution and in the solid state and matched against the properties of its oxygen-free 4,5-diazafluorene congener L and its complexes of the same metal ions. Comprehensive experimental and theoretical studies revealed the impact of the oxygen atom in the ligand core on the luminescence of the ligands and the complexes. For the oxygen-free L ligand and L-based complexes, the structural differences between the S0 and S1 geometries are small, which leads to fluorescence with extraordinarily small Stokes shifts. The emission of these compounds is of locally excited character for L and of mixed locally excited + ligand-to-halide charge transfer character for the L-based complexes. The introduction of the oxygen atom in the ligand core results in a drastic red-shift of the emission band due to short-range charge transfer. The differences between the S0 and S1 geometries are much more pronounced for LO and LO-based compounds than those of their oxygen-free analogues, leading to an order of magnitude larger Stokes shifts. On going from solution to the solid state, LO and its complexes exhibit aggregation-induced emission (AIE) behaviour with photoluminescence quantum yields (PLQYs) reaching tens of percent. [ABSTRACT FROM AUTHOR]

C2‐symmetric terpene‐based bis(α‐amine oximes) prepared from monoterpene hydrocarbons (+)‐3‐carene, (−)‐α‐pinene and (+)‐limonene, when treated with methylene chloride under phase‐transfer conditions, undergo inter‐ and intramolecular cross‐linking at oxime groups to form D2‐symmetric macrocycles in relatively good preparative yields (35–64 %). The structure of the new compounds was solved by spectroscopic methods and proved by X‐ray crystallography. D2‐symmetric macrocycles are crystalline solids which are well soluble even in small amounts of low‐polar organic solvents. Using Microwave Plasma Atomic Emission Spectrometry the new compounds was found to be able to selectively extract some noble metals (PtIV, AuIII, PdII) from aqueous solutions with pH=1.2 containing complex mixtures of transition elements at with no noticeable extraction of d‐elements (CrVI, MnII, FeIII, CoII, NiII, CuII, ZnII) and other noble metals (RuIII, RhIII, IrIII). [ABSTRACT FROM AUTHOR]

A rare example of the palladium–catalyzed sp3 C−H bond activation in a monoterpene‐based compound has been observed in the reaction of PdCl2 with a (+)‐3‐carene‐based ligand HL (HL=N‐((1aS,3S,7bR)‐1,1,3‐trimethyl‐7‐phenyl‐5‐(pyridin‐2‐yl)‐1a,2,3,7b‐tetrahydro‐1H‐cyclopropa[f]quinolin‐3‐yl)acetamide), which yielded the [PdLCl] complex. In contrast to the vast majority of C(sp3)−H activation reactions which require prolonged heating and mixing due to the inert character of the corresponding bond, the reaction reported herein proceeds rapidly under mild conditions. A theoretical insight into the ligand deprotonation has been performed by DFT calculations. The mechanism of the C−H activation involves (i) simultaneous coordination of the CH3 group of HL to the Pd2+ ion and decoordination of the Cl− anion with consequent formation of a Cl⋅⋅⋅H−N hydrogen bond with the amide group, (ii) approximation of the out‐of‐sphere Cl− anion to one of the hydrogen atoms of the CH3 group mediated by the crane motion of the amide group and (iii) the ejection of the HCl molecule, which increases the entropy of the system and serves as a driving force for the reaction. [ABSTRACT FROM AUTHOR]