Optical and electronic properties of lithium thiogallate (LiGaS2): experiment and theory

We report the relation between the optical properties and electronic structure of lithium thiogallate (LiGaS₂) by performing XPS and XES measurements and theoretical calculations. According to the XPS measurements, the LiGaS₂ crystals grown by the Bridgman–Stockbarger method possess promising optical qualities, low hygroscopicity and high stability upon middle-energy Ar⁺-ion irradiation. The difference in the LiGaS₂ band gaps obtained by theoretical calculations and experimental measurements was, for the first time, reduced down to 0.27 eV by applying the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential where the Coulomb repulsion was considered by introducing Hubbard parameter, U. The TB-mBJ+U method also reproduces the XPS spectrum well. The TB-mBJ+U band-structure calculations of LiGaS₂ are found to be in good agreement with the XPS and XES experimental data. The accurate electronic structure of LiGaS₂ allows further investigation of the optical properties. The relation between the photoluminescence of LiGaS₂ and its electronic structure was revealed. Moreover, the theoretical results show the possibility of emissions at higher energy levels in LiGaS₂, that has not been measured in experiments yet. Good phase-matching of LiGaS₂ was expected to occur at energy levels of 5, 6, 6.2, 7, 7.2, and 8 eV.

We report the relation between the optical properties and electronic structure of lithium thiogallate (LiGaS₂) by performing XPS and XES measurements and theoretical calculations.     

Investigation on the electronic structure,optical, elastic,mechanical, thermodynamic and thermoelectric properties of wide band gap semiconductor double perovskite Ba2InTaO6

In the present paper, double perovskite Ba₂InTaO₆ was investigated in terms of its structural, electronic, optical, elastic, mechanical, thermodynamic and thermoelectric properties using density-functional theory (DFT). The generalized gradient approximation (GGA) in the scheme of Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson (mBJ) potential were employed for the exchange–correlation potential. The computed lattice constant was found to be in agreement with the available experimental and theoretical results. The electronic profile shows a semiconducting nature. Further analysis of the complex dielectric constant ε(ω), refractive index n(ω), reflectivity R(ω), absorption coefficient α(ω), optical conductivity (ω) and energy loss function were also reported with the incident photon energy. The elastic constants were also calculated and used to determine mechanical properties like Young''s modulus (Y), the shear modulus (G), Poisson''s ratio (ν) and the anisotropic factor (A). The electrical conductivity (σ/τ) and Seebeck coefficient (S) also demonstrated the semiconducting nature of the compound with electrons as the majority carriers. The value of the power factor was calculated to be 1.20 × 10¹² W K⁻² m⁻¹ s⁻¹ at 1000 K. From thermodynamic investigations, the heat capacity and Grüneisen parameter were also predicted.

In the present paper, double perovskite Ba₂InTaO₆ was investigated in terms of its structural, electronic, optical, elastic, mechanical, thermodynamic and thermoelectric properties using density-functional theory (DFT).     

Correction: Insight into the exemplary structural,elastic, electronic and optical nature of GaBeCl3 and InBeCl3: a DFT study

Correction for ‘Insight into the exemplary structural, elastic, electronic and optical nature of GaBeCl₃ and InBeCl₃: a DFT study’ by Saima Ahmad Shah et al., RSC Adv., 2022, 12, 8172–8177, DOI: 10.1039/D2RA00943A.

The authors regret that three of the authors were associated with the incorrect affiliations. The correct list of authors and affiliations is as shown here.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Theoretical and experimental study on the electronic and optical properties of K0.5Rb0.5Pb2Br5: a promising laser host material

The data on the electronic structure and optical properties of bromide K_0.5Rb_0.5Pb₂Br₅ achieved by first-principle calculations and verified by X-ray spectroscopy measurements are reported. The kinetic energy, the Coulomb potential induced by the exchange hole, spin-orbital effects, and Coulomb repulsion were taken into account by applying the Tran and Blaha modified Becke–Johnson function (TB-mBJ), Hubbard U parameter, and spin-orbital coupling effect (SOC) in the TB-mBJ + U + SOC technique. The band gap was for the first time defined to be 3.23 eV. The partial density of state (PDOS) curves of K_0.5Rb_0.5Pb₂Br₅ agree well with XES K Ll and Br Kβ₂, and XPS spectra. The valence band (VB) is characterized by the Pb-5d_3/2 and Pb-5d_5/2 sub-states locating in the vicinities of −20 eV and −18 eV, respectively. The VB middle part is mainly formed by K-3p, Rb-4p and Br-4s states, in which the separation of Rb-4p_3/2 and Rb-4p_1/2 was also observed. The strong hybridization of Br-p and Pb-s/p states near −6.5 eV reveals a major covalent part in the Br–Pb bonding. With a large band gap of 3.23 eV, and the remarkably high possibility of inter-band transition in energy ranges of 4–7 eV, and 10–12 eV, the bromide K_0.5Rb_0.5Pb₂Br₅ is expected to be a very promising active host material for core valence luminescence and mid-infrared rare-earth doped laser materials. The anisotropy of optical properties in K_0.5Rb_0.5Pb₂Br₅ is not significant, and it occurs at the extrema in the optical spectra. The absorption coefficient α(ω) is in the order of magnitude of 10⁶ cm⁻¹ for an energy range of 5–25 eV.

The data on the electronic structure and optical properties of bromide K_0.5Rb_0.5Pb₂Br₅ achieved by first-principle calculations and verified by X-ray spectroscopy measurements are reported.     

Elucidating π–π interaction-induced extension effect in sandwich phthalocyaninato compounds

Electrochemical and theoretical investigations over triple-quadruple-, quintuple-, and sextuple-decker sandwich-type compounds {[(Pc*)Sm][(Pc*)Cd_n(Pc*)_n][Sm(Pc*)]} (n = 0–3) elucidate successive π–π interaction-linked extension in the perpendicular direction of the phthalocyanine plane along with increasing the stacked tetrapyrrole number, significantly improving the nonlinear optical properties including effective imaginary third order molecular hyperpolarizability and optical limiting threshold.

π–π interaction-linked extension in the perpendicular direction to the monomers and corresponding effect on nonlinear optic properties have been clearly disclosed over the multiple-decker sandwich-type phthalocyaninato metal compounds.     

Impact of tunable 2-(1H-indol-3-yl)acetonitrile based fluorophores towards optical,thermal and electroluminescence properties

Herein, we have synthesized 4,5-diphenyl-1H-imidazole and 2-(1H-indol-3-yl)acetonitrile based donor–π–acceptor fluorophores and studied their optical, thermal, electroluminescence properties. Both the fluorophores exhibit high fluorescence quantum yield (Φ_f = <0.6) and good thermal stability (T_d10 = <300 °C), and could be excellent candidates for OLED applications. Moreover, the ground and excited state properties of the compounds were analysed in various solvents with different polarities. The geometric and electronic structures of the fluorophores in the ground and excited states have been studied using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The absorption of BIPIAN and BITIAN in various solvents corresponds to S₀ → S₁ transitions and the most intense bands with respect to the higher oscillator strengths are mainly contributed by HOMO → LUMO transition. Significantly, the vacuum deposited non-doped OLED device was fabricated using BITIAN as an emitter, and the device shows electroluminescence (EL) at 564 nm, maximum current efficiency (CE) 0.687 cd A⁻¹ and a maximum external quantum efficiency (EQE) of 0.24%.

Herein, we have synthesized 4,5-diphenyl-1H-imidazole and 2-(1H-indol-3-yl)acetonitrile based donor–π–acceptor fluorophores and studied their optical, thermal, electroluminescence properties.     

Behaviour of the XH-*-π and YX-*-π interactions (X,Y = F,Cl, Br and I) in the coronene π-system,as elucidated by QTAIM dual functional analysis with QC calculations

The dynamic and static nature of XH-*-π and YX-*-π in the coronene π-system (π(C₂₄H₁₂)) is elucidated by QTAIM dual functional analysis, where * emphasizes the presence of bond critical points (BCPs) in the interactions. The nature of the interactions is elucidated by analysing the plots of the total electron energy densities H_b(r_c) versus H_b(r_c) − V_b(r_c)/2 [=(ħ²/8m)∇²ρ_b(r_c)] for the interactions at BCPs, where V_b(r_c) are the potential energy densities at the BCPs. The data for the perturbed structures around the fully optimized structures are employed for the plots in addition to those of the fully optimized structures. The plots are analysed using the polar coordinate of (R, θ) for the data of the fully optimized structures, while those containing the perturbed structures are analysed using (θ_p, κ_p), where θ_p corresponds to the tangent line of each plot and κ_p is the curvature. Whereas (R, θ) show the static nature, (θ_p, κ_p) represent the dynamic nature of the interactions. All interactions in X–H-*-π(C₂₄H₁₂) (X = F, Cl, Br and I) and Y–X-*-π(C₂₄H₁₂) (Y–X = F–F, Cl–Cl, Br–Br, I–I, F–Cl, F–Br and F–I) are classified by pure CS (closed shell) interactions and are characterized as having the vdW nature, except for X–H = F–H and Y–X = F–Cl, F–Br and F–I, which show the typical-HB nature without covalency. The structural features of the complexes are also discussed.

The XH-*-π(C₂₄H₁₂) interactions appear on the outside ring of C₂₄H₁₂, while YX-*-π(C₂₄H₁₂) do both on the inside and outside rings.     

Comparison of ±σ-hole and ±R˙-hole interactions formed by tetrel-containing complexes: a computational study

For the first time, unconventional ^±R˙-hole interactions were unveiled in tetrel-containing complexes. The nature and characteristics of ^±R˙-hole interactions were explored relative to their ^±σ-hole counterparts for ˙TF₃⋯ and W–T–F₃⋯B/R˙/A complexes (where T = C, Si, and Ge, W = H and F, B = Lewis bases, R˙ = free radicals, and A = Lewis acids). In an effort to thoroughly investigate such interactions, a plethora of quantum mechanical calculations, including molecular electrostatic potential (MEP), maximum positive electrostatic potential (V_s,max), point-of-charge (PoC), interaction energy, symmetry adapted perturbation theory (SAPT), and reduced density gradient–noncovalent interaction (RDG–NCI) calculations, were applied. The most notable findings to emerge from this study are that (i) from the electrostatic perspective, the molecular stabilization energies of ˙TF₃ and W–T–F₃ monomers became more negative as the Lewis basicity increased, (ii) the most stable complexes were observed for the ones containing Lewis bases, forming ⁻σ-hole and ⁻R˙-hole interactions, and the interaction energies systematically increased in the order H–T–F₃⋯B < ˙TF₃⋯B < F–T–F₃⋯B, (iii) contrariwise, the ⁺σ-hole and ⁺R˙-hole interactions with Lewis acids are more energetically favorable in the order F–T–F₃⋯A < ˙TF₃⋯A < H–T–F₃⋯A, and (iv) generally, the dispersion force plays a key role in stabilizing the tetrel-containing complexes, jointly with the electrostatic and induction forces for the interactions with Lewis bases and acids, respectively. Concretely, the findings presented in this paper add to our understanding of the characteristics and nature of such intriguing interactions.

The characteristics and nature of ^±R˙-hole interactions were uncovered for the first time and compared to their ^±σ-hole analogs in ˙TF₃⋯ and W–T–F₃⋯B/R˙/A complexes.     

Low pH constructed Co(ii) and Ni(ii) 1D coordination polymers based on Cα-substituted analogues of zoledronic acid: structural characterization,and spectroscopic and magnetic properties

Three novel coordination compounds based on α,α-disubstituted analogues of zoledronic acid with a cyclopropane (cpp) or cyclobutane (cbt) ring on the C_α carbon, isomorphous [Co(H₂cppZol)(H₂O)]·H₂O (1a), [Ni(H₂cppZol)(H₂O)]·H₂O (1b) and [Co(H₂cbtZol)(H₂O)]·H₂O (2a), were synthesized under hydrothermal conditions at low pH. Single-crystal X-ray diffraction analysis revealed that all the compounds had a 1D double zig–zag chain architecture with an 8 + 8 ring motif formed by alternately arranged symmetrical (–O–P–O–)₂ bridges linking equivalent octahedral metal centres. Both the ligand coordination mode and chain architecture displayed by 1a, 1b and 2a are unique among 1D [M(H₂L)(H₂O)_x]·yH₂O coordination polymers based on nitrogen-containing bisphosphonates reported so far. All the compounds exhibit similar decomposition pathways upon heating with thermal stabilities decreasing in the order 1b > 1a > 2a. The IR spectra revealed that lattice water release above 227, 178 and 97 °C, respectively, does not change the chain architecture leaving them intact up to ca. 320, 280 and 240 °C. Magnetic behaviour investigations indicated that 1a, 2a and 1b exhibit weak alternating antiferromagnetic–ferromagnetic exchange interactions propagated between the magnetic centres through double (–O–P–O–)₂ bridges. The boundary between antiferro- and ferromagnetic couplings for the Co–O⋯O–Co angle in 1a and 2a was estimated to be ca. 80°. This value is also applicable for recently reported [M₃(HL)₂(H₂O)₆]·6H₂O (M = Co, Ni) complexes based on α,α-disubstituted analogues of zoledronic acid and can be used to the explain magnetic behaviour of 1b.

1D Co(ii)/Ni(ii) coordination polymers with alternating antiferromagnetic–ferromagnetic exchange interactions between metal centers propagated through double (–O–P–O–)₂ bridges.     

Effect of Bi-substitution into the A-site of multiferroic La0.8Ca0.2FeO3 on structural,electrical and dielectric properties

(La_0.8Ca_0.2)_1−xBi_xFeO₃ (x = 0.00, 0.05, 0.10, 0.15 and 0.20) (LCBFO) multiferroic compounds have been prepared by the sol–gel method and calcined at 800 °C. X-ray diffraction results have shown that all samples crystallise in the orthorhombic structure with the Pnma space group. Electrical and dielectric characterizations of the synthesized materials have been performed using complex impedance spectroscopy techniques in the frequency range from 100 Hz to 1 MHz and in a temperature range from 170 to 300 K. The ac-conductivity spectra have been analysed using Jonscher''s power law σ(ω) = σ_dc + Aω^s, where the power law exponent (s) increases with the temperature. The imaginary part of the complex impedance (Z′′) was found to be frequency dependent and shows relaxation peaks that move towards higher frequencies with the increase of the temperature. The relaxation activation energy deduced from the Z′′ vs. frequency plots was similar to the conduction activation energy obtained from the conductivity. Hence, the relaxation process and the conduction mechanism may be attributed to the same type of charge carriers. The Nyquist plots (Z′′ vs. Z′) at different temperatures revealed the appearance of two semi-circular arcs corresponding to grain and grain boundary contributions.

(La_0.8Ca_0.2)_1−xBi_xFeO₃ (x = 0.00, 0.05, 0.10, 0.15 and 0.20) (LCBFO) multiferroic compounds have been prepared by the sol–gel method and calcined at 800 °C.     

Effect of methylene chain length of perovskite-type layered [NH3(CH2)nNH3]ZnCl4 (n = 2, 3, and 4) crystals on thermodynamic properties,structural geometry,and molecular dynamics

The structure of organic–inorganic perovskite [NH₃(CH₂)₄NH₃]ZnCl₄ was determined; the lattice constants with monoclinic structure were determined to be a = 7.2527 Å, b = 8.1101 Å, c = 10.3842 Å, and β = 80.3436°. The crystal was almost thermally stable up to approximately 560 K. The endothermic peaks at 481 K and 506 K were assigned to the phase transition of the material. In addition, the structural characteristics and molecular dynamics of the cation were studied via magic angle spinning nuclear magnetic resonance experiments. Based on the results, the effects of the length of the CH₂ group in the cation of the [NH₃(CH₂)_nNH₃]ZnCl₄ (n = 2, 3, and 4) crystals were considered. Regardless of whether n was even or odd, the differences in the thermal and physical properties were minimal. Moreover, a difference in molecular motion relative to the length of the cation was observed only at high temperatures. These results provide useful information about the thermal stability and molecular dynamics of [NH₃(CH₂)_nNH₃]ZnCl₄ crystals and are expected to facilitate potential applications of such compounds in supercapacitors, batteries, and fuel cells.

¹H NMR spin–lattice relaxation times T_1ρ of [NH₃(CH₂)_nNH₃]ZnCl₄ (n = 2, 3, and 4) as a function of inverse temperature. The solid lines represent activation energy.     

Hexanuclear Cu3O–3Cu triazole-based units as novel core motifs for high nuclearity copper(ii) frameworks

The asymmetric 3,5-disubstituted 1,2,4-triazole ligand H₂V (5-amino-3-picolinamido-1,2,4-triazole) by reaction with an excess of Cu(ii) perchlorate (Cu : H₂V being 12 : 1) has produced a novel hexanuclear {Cu₆(μ₃-O/H)(HV/V)₃} fragment, with one triangular Cu₃(μ₃-O/H) group connected to three peripheral single Cu(ii) ions through a cis–cis–trans bridging mode of the ligand, which is the building block of the three structures described here: one hexanuclear, [Cu₆(μ₃-O)(HV)₃(ClO₄)₇(H₂O)₉]·8H₂O (1), one dodecanuclear, [Cu₁₂(μ₃-O)₂(V)₆(ClO₄)₅(H₂O)₁₈](ClO₄)₃·6H₂O (2), and one tetradecanuclear 1D-polymer, {[Cu₁₄(μ₃-OH)₂(V)₆(HV)(ClO₄)₁₁(H₂O)₂₀](ClO₄)₂·14H₂O}_n (3), the last two containing hexanuclear subunits linked by perchlorato bridges. The Cu–Cu av. intra-triangle distance is 3.352(2) Å and the Cu(central)–Cu(bridged external) av. distance is 5.338(3) Å. The magnetic properties of the hexanuclear “Cu₃O–3Cu” cluster have been studied, resulting as best fit parameters: g = 2.18(1), J(intra-triangle) = −247.0(1) cm⁻¹ and j(central Cu^II – external Cu^II) = −5.15(2) cm⁻¹.

The novel hexanuclear {Cu₆(μ₃-O/H)(HV/V)₃} fragment is the building block of the hexanuclear, the dodecanuclear and the tetradecanuclear-1D-polymeric structures described here.     

Ferroelectric properties and Raman spectroscopy of the [(C4H9)4N]3Bi2Cl9 compound

The exploration of ferroelectric hybrid materials is highly appealing due to their great technological significance. They have the potential to conserve power and amazing applications in information technology. In line with this, we herein report the development of a [(C₄H₉)₄N]₃Bi₂Cl₉ tetra-alkyl hybrid compound that exhibits ferroelectric properties. The phase purity was confirmed by Rietveld refinement of the X-ray powder diffraction pattern. It crystallizes, at room temperature, in the monoclinic system with the P2₁/n space group. The outcome of temperature dependence of the dielectric constant proved that this compound is ferroelectric below approximately 238 K. The dielectric constants have been fitted using the modified Curie–Weiss law and the estimated γ values are close to 1. This confirms classical ferroelectric behavior. Raman spectroscopy is efficiently utilized to manifest the origin of the ferroelectricity, which is ascribed to the dynamic motion of cations as well as distortion of the anions. Moreover, the analysis of the wavenumbers and the half-width for δ_s(Cl–Bi–Cl) and ω(CH₂) modes, based on the order–disorder model, allowed us to obtain the thermal coefficient and activation energy near the para-ferroelectric phase transition.

The exploration of ferroelectric hybrid materials is highly appealing due to their great technological significance.     

Anomalous behavior above the Curie temperature in (Nd1−xGdx)0.55Sr0.45MnO3 (x = 0, 0.1, 0.3 and 0.5)

Magnetic properties were studied just above the ferromagnetic–paramagnetic (FM–PM) phase transition of (Nd_1−xGd_x)_0.55Sr_0.45MnO₃ with x = 0, 0.1, 0.3 and 0.5. The low-field inverse susceptibility (χ⁻¹) of Nd_0.55Sr_0.45MnO₃ exhibits a Curie–Weiss-PM behavior. For x ≥ 0.1, we observe a deviation in χ⁻¹(T) behavior from the Curie–Weiss law. The anomalous behavior of the χ⁻¹(T) was qualified as Griffiths phase (GP)-like. The study of the evolution of the GP through a susceptibility exponent, the GP temperature and the temperature range of the GP reveals that the origin of the GP is primary due to the accommodated strain. Likewise, the magnetic data reveal distinct features visible only for x = 0.5 at a low magnetic field that can be qualitatively understood as the result of ferromagnetic polarons, entailed by the strong effect of chemical/structural disorder, whose concentration increases upon cooling towards the Curie temperature. We explained the magnetic properties at a high temperature for the heavily Gd-doped sample (x = 0.5) within the phase-separation scenario as an assembly of ferromagnetic nanodomains, antiferromagnetically coupled by correlated Jahn–Teller polarons.

Magnetic properties were studied just above the ferromagnetic–paramagnetic (FM–PM) phase transition of (Nd_1−xGd_x)_0.55Sr_0.45MnO₃ with x = 0, 0.1, 0.3 and 0.5.     

The nature of G⋯E–Y σ(3c–4e) in o-MenGCH2C6H4EY (MenG = Me2N and MeE; E = O,S, Se and Te; Y = F,Cl, Br,EMe and Me) with contributions from CT and compliance constants in noncovalent G⋯E interactions

The intrinsic dynamic and static nature of G–*–E–*–Y σ(3c–4e) interactions was elucidated with the quantum theory of atoms in molecules dual functional analysis (QTAIM-DFA), employing o-Me_nGCH₂C₆H₄EY (Me_nG = Me₂N and MeE; E = O, S, Se and Te; Y = F, Cl, Br, I, EMe and Me). Asterisks (*) are employed to emphasize the existence of bond critical points (BCPs) on the bond paths (BPs), corresponding to the interactions in question. Data from the fully optimized structure correspond to the static nature of interactions. The dynamic nature is called the intrinsic dynamic nature if the perturbed structures are generated using the coordinates derived from the compliance constants. Basis sets of the Sapporo-TZP type with diffusion functions are employed for the heteroatoms at the MP2 level. The noncovalent G–*–E interactions in GEY σ(3c–4e) are predicted to demonstrate van der Waals bonding to CT-TBP (trigonal bipyramidal adduct formation through charge transfer) nature, while the E–*–Y bonds have the covalent nature. Some E–F bonds show strong ionic character when G–*–E is predicted to be stronger than E–*–Y. The contributions of the CT terms to the G–*–E interactions, evaluated with NBO, are discussed in relation to the predicted nature. The E(2) values based on NBO are strongly correlated to the compliance constants for the G–*–E interactions if suitably treated separately.

The nature of E⋯E′ in 1-RECH₂-2-R′E′C₆H₄ (E/E′ = O, S, Se and Te) is clarified with QTAIM approach and NBO analysis, after structural determinations.     

A series of lanthanide–quinoxaline-2,3(1H,4H)-dione complexes containing 1D chiral Ln2O3 (Ln = Eu,Tb, Sm,Dy) chains: luminescent properties and response to small molecules

Five new isostructural lanthanide–organic complexes, [Ln₂O₂(OH)(HQXD)(H₂QXD)₂]·H₂O (Ln = Eu 1, Tb 2, Sm 3 Dy 4 and Gd 5; H₂QXD = quinoxaline-2,3(1H,4H)-dione), have been synthesized under hydrothermal conditions. These complexes are characterized by powder X-ray diffraction (PXRD), infrared spectroscopy (IR), elemental analysis (EA), thermogravimetric-differential thermal analysis (TG-DTA) and photo-luminescent spectroscopy. Single crystal X-ray diffraction analysis of complex 1 revealed that the structure featured in 1D chiral “Eu₂O₃” chains surrounded by coordinating organic ligands. These chains are interconnected via hydrogen bonding and offset π⋯π stacking interactions of the ligands to form the 3D supramolecular frameworks. The photo-luminescence studies for complexes 1–5 disclosed that the ligand (H₂QXD) showed an antenna effect to transfer energy toward the lanthanide cations. The energy transfer mechanism investigations show that the energy transition from the triplet energy level (³ππ*) of ligand H₂QXD to the Tb³⁺ cation is more effective than to the Eu³⁺, Sm³⁺ and Dy³⁺ ions; therefore it has been selected as a representative to examine the potential for sensing small molecules. Complex 2′, which was obtained by the heating treatment of 2 at 150 °C, displayed a high luminescence sensitivity towards small solvent molecules. Tertiary butanol (t-butanol) was found to be an excellent sensitizer, while tetrahydrofuran (THF) was a highly quenching species. Complex 2′ could regain a higher photo-luminescence intensity after treating for 5 cycles with t-butanol, revealing a prospect for reusability.

A series of isostructural lanthanide–quinoxaline-2,3(1H,4H)-dione containing 1D chiral chains shows high sensing effect toward the small solvent molecules, in which tertiary butanol was an excellent sensitizer, while tetrahydrofuran was a highly quenching species.     

Hot exciton transition for organic light-emitting diodes: tailoring excited-state properties and electroluminescence performances of donor–spacer–acceptor molecules

The photophysical, electrochemical and electroluminescent properties of newly synthesized blue emitters with donor–π–acceptor geometry, namely, 4′-(1-(naphthalen-1-yl)-1H-phenanthro[9,10-d]imidazol-2-yl)-N,N-diphenyl-(2-[1,1′-biphenyl]vinyl)-4-amine (NSPI-TPA), 4′-(1-(2-methylnaphthalen-1-yl)-1H-phenanthro[9,10-d]imidazol-2-yl)-N,N-diphenyl-(2-[1,1′-biphenyl]vinyl)-4-amine (MNSPI-TPA), 4-(2-(4′-(diphenylamino)-(2-[1,1′-biphenyl]vinyl)-4-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)-1-naphthalene-1-carbonitrile (SPNCN-TPA) and 4-(2-(4-(9H-carbazol-9-yl)styryl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile (SPNCN-Cz) were analyzed. The conjugation length in the emitters is not conducive to pure emission and hence, a molecular twisting strategy was adopted in NSPI-TPA, MNSPI-TPA, SPNCN-TPA and SPNCN-Cz to enhance pure emission. The emissive state (HLCT) of twisted D–π–A molecules containing both LE and CT (HLCT) states was tuned for high PL (η_PL) (LE) and high exciton utilization (η_s) (CT) efficiencies by replacing triphenylamine (strong donor) with carbazole (weak donor). Among strong donor compounds, namely, NSPI-TPA, MNSPI-TPA and SPNCN-TPA, the SPNCN-TPA-based device exhibited blue emission (451 nm) with CIE coordinates (0.15, 0.08), maximum current efficiency (η_c) of 2.32 cd A⁻¹, power efficiency (η_p) of 2.01 lm W⁻¹ and external quantum efficiency (η_ex) of 3.02%. The device with SPNCN-Cz emitter exhibited higher electroluminescence efficiencies than the SPNCN-TPA-based device, with pure blue emission (443 nm, CIE: 0.15,0.07), η_ex of 3.15%, η_c of 2.56 cd A⁻¹ and η_p of 2.45 lm W⁻¹.

SPNCN-Cz device exhibits η_ex (3.15%), η_c (2.56 cd A⁻¹), η_p (2.45 lm W⁻¹) with CIE (0.15, 0.07).     

Comparative investigation of interactions of hydrogen,halogen and tetrel bond donors with electron-rich and electron-deficient π-systems

Recently, noncovalent interactions in complexes and crystals have attracted considerable interest. The current study was thus designed to gain a better understanding of three seminal types of noncovalent interactions, namely: hydrogen, halogen and tetrel interactions with π-systems. This study was performed on three models of Lewis acids: X₃–C–H, F₃–C–X and F–T–F₃ (where X = F, Cl, Br and I; and T = C, Si, Ge and Sn) and three π-systems as Lewis bases: benzene (BZN), 1,3,5-trifluorobenzene (TFB) and hexafluorobenzene (HFB). Quantum mechanical calculations, including geometrical optimization, molecular electrostatic potential (MEP), maximum positive electrostatic potential (V_s,max), Point-of-Charge (PoC), potential energy surface (PES), quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) calculations, were carried out at the MP2/aug cc-pVDZ level of theory. The binding energies were additionally benchmarked at the CCSD(T)/CBS level. The results showed that: (i) the binding energies of the X₃–C–H⋯π-system complexes were unexpectedly inversely correlated with the V_s,max values on the hydrogen atom but directly correlated with the X atomic sizes; (ii) the binding energies for the F₃–C–X⋯π-system and F–T–F₃⋯π-system complexes were correlated with the σ-hole magnitudes of the X and T atoms, respectively; and (iii) for the F₃–C–F⋯π-system complexes, the binding energy was as strong as the π-system was electron-deficient, indicating the dominating nucleophilic character of the fluorine atom. NCI analysis showed that the unexpected trend of X₃–C–H⋯π-system binding energies could be attributed to additional attractive interactions between the X atoms in the X₃–C–H molecule and the carbon atoms of the π-system. Furthermore, the I₃–Sn–H molecule was employed as a case study of hydrogen, halogen and tetrel interactions with π-systems. It was found that hydrogen and halogen interactions of the I₃–Sn–H molecule correlated with the electron-richness of the π-system. In contrast, tetrel interactions correlated with the electron deficiency of the π-system.

Three seminal types of noncovalent interaction, namely: hydrogen, halogen and tetrel interactions with π-systems, were investigated using quantum mechanical calculations.     

Four new Zn(ii) and Cd(ii) coordination polymers using two amide-like aromatic multi-carboxylate ligands: synthesis,structures and lithium–selenium batteries application

Four new coordination polymers, {[Zn(3-PBI)(H₂O)]·2DMF}_n (1), [Cd(3-PBI)(DMF)]_n (2), {[Zn₄(μ₄-O)(4-PBI)₃]·3DMF}_n (3), {[Cd₄(4-PBI)₄(H₂O)₆]·13H₂O}_n (4), have been constructed from two isomeric flexible multi-carboxylate ligands, 3-H₂PBI = 5-(3-(pyridin-3-yl)benzamido)isophthalic acid and 4-H₂PBI = 5-(3-(pyridin-4-yl)benzamido)isophthalic acid. Structural analysis reveals that compound 1 is a one-dimensional (1D) ladder-like chain assembled by Zn(ii) ions and 3-PBI²⁻ ligands, which further extend into a 3D supramolecular structure through π⋯π stacking and interlayer (O–H⋯O) hydrogen bonding interactions. In compound 2, Cd²⁺ metal ions are connected by carboxylate groups to form [Cd₂(COO)₄] secondary building units (SBUs). The whole framework possesses a quadrilateral channel and constitutes a unique 3D (3,6)-connected rutile net with the Schläfli symbol of (4²·6¹⁰·8³)(4·6²)₂. As for 3, Zn(ii) ions are bridged by one μ₄-O and six carboxylate groups to form a tetranuclear [Zn₄(μ₄-O)(COO)₆] cluster, resulting in a rare (3,9)-connected 3D network. Compound 4 has an appealing 2D layered architecture involving two distinct topologies in the crystal structure, stacking in an unusual ABBABB mode (where A represents (4·8²) topology and B denotes kgd topology). Moreover, compound 2 is prepared as a support for active selenium through a melt-diffusion method. The obtained Cd-CP/Se electrode can be tested for lithium–selenium batteries and shows an initial capacity of 514 mA h g⁻¹ and a reversible capacity of 200 mA h g⁻¹ at 1C after 500 cycles. The good storage performance of Cd-CP/Se demonstrates it to be a prospective cathode material for lithium–selenium batteries.

Four new coordination polymers were constructed and compound 2 was used as a host to active selenium for Li–Se batteries.     

Four 3D coordination polymers based on layers with single syn–anti carboxylate bridges: synthesis,structures, and magnetic properties

Four novel coordination polymers (CPs) based on a new 4-(3,5-dicarboxylphenyl) picolinic acid ligands (H₃L), [M₃(L)₂(H₂O)₆]·4H₂O (M₃ = Mn₃, 1; Co₃, 2; Ni₃, 3, Co_1.01Ni_1.99, 4), have been hydrothermally synthesized, and structurally and magnetically characterized. In these isomorphous CPs, octahedrally coordinated metal ions are linked by the single syn–anti carboxylate bridge (μ-COO) to give linear trinuclear motifs. The motifs are connected through the other single syn–anti carboxylate bridge (μ-COO) to give a 2D (4,4) layer, and the layers are interlinked by the L ligands into 3D frameworks. Magnetic measurement indicates that antiferromagnetic interactions between metal ions are mediated through the single syn–anti carboxylate bridges in 1 and 2, while the same carboxylate bridges in 3 transmit ferromagnetic couplings. The bimetallic CP 4 shows interesting complicated magnetic behaviors due to the competition effect of Co(ii) and Ni(ii) ions.

Four 3D carboxylate-bridged metal(II) compounds were prepared. Mn(II) and Co(II) compounds show AFM interactions, while FM coupling is found in Ni(II) compound. The bimetallic shows interesting competition effect of FM and AFM interactions.