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.     

A new family of decanuclear Ln7Cr3 clusters exhibiting a magnetocaloric effect

Two dimeric Ln–Cr clusters with formula {Ln(H₂O)₈[Ln₆Cr₃(L)₆(CH₃COO)₆(μ₃-OH)₁₂(H₂O)₁₂]}·(ClO₄)₆·xH₂O (Ln = Gd, x = 35 for 1 and Ln = Dy, x = 45 for 2, HL = 2-pyrazinecarboxylic acid) were obtained by a ligand-controlled hydrolytic method with a mixed ligand system (2-pyrazinecarboxylic acid and acetate). Single crystal structure analysis showed that two trigonal bipyramids of [Gd₃Cr₂(μ₃-OH)₆]⁹⁺ worked as building blocks in constructing the metal-oxo cluster core of [Gd₆Cr₃(μ₃-OH)₁₂]¹⁵⁺ by sharing a common top – a Cr³⁺ ion. Additionally, compound 1 forms a three-dimensional framework with a one-dimensional nanopore channel along the a-axis through a hydrogen-bond interaction between the cationic cluster core and the free mononuclear cation [Gd(H₂O)₈]³⁺ and the π-bond interactions of the pyrazine groups on the two cationic cluster cores. Magnetic calculations indicated a weak ferromagnetic coupling interaction for Gd⋯Gd and Gd⋯Cr in compound 1, with its magnetic entropy change (−ΔS_m) reaching 21.1 J kg⁻¹ K⁻¹ at 5 K, 7 T, while compound 2 displayed an obvious frequency-dependency at H_dc = 2000 Oe.

Two decanuclear Ln–Cr clusters Ln₇Cr₃ were obtained, which formed a three-dimensional framework with one-dimensional nanopore channel through hydrogen-bond and π-bond interactions. Gd₇Cr₃ had a magnetic entropy change of 21.1 J kg⁻¹ K⁻¹ at 5 K, 7 T.     

Synthesis,crystal structures and magnetic properties of two heterometallic {Ln8Cr4} (Ln = Gd3+ and Tb3+) complexes with one-dimensional wave chain structure

Two isomorphic heterometallic 3d–4f cluster-based materials, formulated [Gd₈Cr₄(IN)₁₈(μ₃-O)₂(μ₃-OH)₆(μ₄-O)₄(H₂O)₁₀]·13H₂O (1) and [Tb₈Cr₄(IN)₁₈(μ₃-O)₂(μ₃-OH)₆(μ₄-O)₄(H₂O)₁₀]·13H₂O (2) (abbreviation: {Ln₈Cr₄}: Ln = Gd³⁺ (1); Tb³⁺ (2); HIN = isonicotinic acid), were achieved by hydro-/solvothermal method through using the ligand HIN. X-ray diffraction analysis illustrates eight lanthanide ions (Ln = Gd³⁺, Tb³⁺) and four transition-metal ions (Cr³⁺) of {Ln₈Cr₄} were constructed from two classical “drum-like” {Ln₄Cr₂} structures associated by organic ligands HIN, displaying a one-dimensional wave chain structure, which is rare. The magnetic properties of {Gd₈Cr₄} were inspected and showed the existence of antiferromagnetic coupling interactions between contiguous metal ions. On top of this, the magnetic entropy change of ΔS_m can attain 23.40 J kg⁻¹ K⁻¹ (44.90 mJ cm⁻³ K⁻¹) at about 3 K and ΔH = 7 T. Besides, fluorescence measurements of {Tb₈Cr₄} display typical characteristic Tb-based luminescence.

Two heterometallic cluster {Ln₈Cr₄} were constructed from two classical “drum-like” {Ln₄Cr₂} building units associated by organic ligands HIN, displaying 1D wave chain structure. The MCE values for {Gd₈Cr₄} at 3 K and 7 T is 23.40 J kg⁻¹ K⁻¹.     

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.     

High-resolution X-ray diffraction determination of the electron density of 1-(8-PhSC10H6)SS(C10H6SPh-8′)-1′ with the QTAIM approach: evidence for S4 σ(4c–6e) at the naphthalene peri-positions

An extended hypervalent S₄ σ(4c–6e) system was confirmed for the linear ^BS-∗-^AS-∗-^AS-∗-^BS interaction in 1-(8-Ph^BSC₁₀H₆)^AS–^AS(C₁₀H₆^BSPh-8′)-1′ (1) via high-resolution X-ray diffraction determination of electron densities. The presence of bond critical points (BCPs; ∗) on the bond paths confirms the nature and extent of this interaction. The recently developed QTAIM dual functional analysis (QTAIM-DFA) approach was also applied to elucidate the nature of the interaction. Total electron energy densities H_b(r_c) were plotted versus H_b(r_c) − V_b(r_c)/2 for the interaction at the BCPs, where V_b(r_c) represents the potential energy densities at the BCP. The results indicate that although the data for an interaction in the fully optimized structure corresponds to a static nature, the data obtained for the perturbed structures around it represent the dynamic nature of the interaction in QTAIM-DFA. The former classifies the interaction and the latter characterises it. Although ^AS-∗-^AS in 1 is classified by a shared shell interaction and exhibits weak covalent character, ^AS-∗-^BS is characterized as having typical hydrogen-bond nature with covalent properties in the region of the regular closed shell interactions. The experimental results are supported by matching theoretical calculations throughout, particularly for the extended hypervalent E₄ σ(4c–6e) (E = S) interaction.

The nature of S₄ σ(4c–6e) at the 1,8-positions of naphthalene is elucidated via a high-resolution X-ray method with the QTAIM approach.     

Development of rapid and selective epoxidation of α-pinene using single-step addition of H2O2 in an organic solvent-free process

This study reports substantial improvement in the process for oxidising α-pinene, using environmentally friendly H₂O₂ at high atom economy (∼93%) and selectivity to α-pinene oxide (100%). The epoxidation of α-pinene with H₂O₂ was catalysed by tungsten-based polyoxometalates without any solvent. The variables in the screening parameters were temperatures (30–70 °C), oxidant amount (100–200 mol%), acid concentrations (0.02–0.09 M) and solvent types (i.e., 1,2-dichloroethane, toluene, p-cymene and acetonitrile). Screening the process parameters revealed that almost 100% selective epoxidation of α-pinene to α-pinene oxide was possible with negligible side product formation within a short reaction time (∼20 min), using process conditions of a 50 °C temperature in the absence of solvent and α-pinene/H₂O₂/catalyst molar ratio of 5 : 1 : 0.01. A kinetic investigation showed that the reaction was first-order for α-pinene and catalyst concentration, and a fractional order (∼0.5) for H₂O₂ concentration. The activation energy (E_a) for the epoxidation of α-pinene was ∼35 kJ mol⁻¹. The advantages of the epoxidation reported here are that the reaction could be performed isothermally in an organic solvent-free environment to enhance the reaction rate, achieving nearly 100% selectivity to α-pinene oxide.

Products obtained from the oxidation of α-pinene with hydrogen peroxide (H₂O₂) in the presence of tungsten-based polyoxometalates (α-pinene 1, α-pinene oxide 2, pinanediol 3, campholenic aldehyde 4, sobrerol 5, verbenol 6 and verbenone 7).     

Copper coordination compounds with (5Z,5Z′)-2,2′-(alkane-α,ω-diyldiselenyl)-bis-5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones. Comparison with sulfur analogue

A series of new organic ligands (5Z,5Z′)-2,2′-(alkane-α,ω-diyldiselenyl)-bis-5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones (L) consisting of two 5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-one units linked with polymethylene chains of various lengths (n = 2–10, where n is the number of CH₂ units) have been synthesized. The reactions of these ligands with CuCl₂·2H₂O and CuClO₄·6H₂O gave Cu²⁺ or Cu¹⁺ containing mono- and binuclear complexes with Cu₂LCl_x (x = 2–4) or CuL(ClO₄)_y (y = 1, 2) composition. It was shown that the agents reducing Cu²⁺ to Cu¹⁺ in the course of complex formation can be both a ligand and an organic solvent in which the reaction is carried out. This fundamentally distinguishes the selenium-containing ligands L from their previously described sulfur analogs, which by themselves are not capable of reducing Cu²⁺ during complexation under the same conditions. A higher cytotoxicity and reasonable selectivity to cancer cell lines for synthesized complexes of selenium-containing ligands was shown; unlike sulfur analogs, ligands L themselves demonstrate a high cytotoxicity, comparable in some cases to the toxicity of copper-containing complexes.

Mono- and binuclear Cu(+1/+2) complexes of bis-5-(2-pyridyimethylene)-2-selenohydantoins were obtained by the reactions of corresponding ligands with copper(+2) chloride or perchlorate in BuOH/DCM mixtures.     

Synthesis,spectroscopic, thermal,antimicrobial and electrochemical characterization of some novel Ru(iii), Pt(iv) and Ir(iii) complexes of pipemidic acid

Three new solid complexes of pipemidic acid (Pip–H) with Ru³⁺, Pt⁴⁺ and Ir³⁺ were synthesized and characterized. Pipemidic acid acts as a uni-dentate chelator through the nitrogen atom of the –NH piperazyl ring. The spectroscopic data revealed that the general formulas of Pip–H complexes are [M(L)_n(Cl)_x]·yH₂O ((1) M = Ru³⁺, L: Pip–H, n = 3, x = 3, y = 6; (2) M = Pt⁴⁺, L: Pip–NH₄, n = 2, x = 4, y = 0 and (3) M = Ir³⁺, L: Pip–H, n = 3, x = 3, y = 6). The number of water molecules with their locations inside or outside the coordination sphere were assigned via thermal analyses (TG, DTG). The DTG curves refer to 2–3 thermal decomposition steps where the first decomposition step at a lower temperature corresponds to the loss of uncoordinated water molecules followed by the decomposition of Pip–H molecules at higher temperatures. Thermodynamic parameters (E*, ΔS*, ΔH* and ΔG*) were calculated from the TG curves using Coats–Redfern and Horowitz–Metzeger non-isothermal models. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were carefully used to assign properly the particle sizes of the prepared Pip–H complexes. The biological enhancement of Pip–H complexes rather than free chelate were assessed in vitro against four kinds of bacteria G(+) (Staphylococcus epidermidis and Staphylococcus aureus) and G(−) (Klebsiella and Escherichia coli) as well as against the human breast cancer (MCF-7) tumor cell line.

Three new solid complexes of pipemidic acid (Pip–H) with Ru³⁺, Pt⁴⁺ and Ir³⁺ were synthesized and characterized. Pipemidic acid acts as a uni-dentate chelator through the nitrogen atom of the –NH piperazyl ring.     

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.     

Catalytic effect of (H2O)n (n = 1–3) clusters on the HO2 + SO2 → HOSO + 3O2 reaction under tropospheric conditions

The HO₂ + SO₂ → HOSO + ³O₂ reaction, both without a catalyst and with (H₂O)_n (n = 1–3) as a catalyst, has been investigated using CCSD(T)/CBS//M06-2X/aug-cc-pVTZ methods, and canonical variational transition state theory with small curvature tunneling (CVT/SCT). The calculated results show that H₂O exerts the strongest catalytic role in the hydrogen atom transfer processes of HO₂ + SO₂ → HOSO + ³O₂ as compared with (H₂O)₂ and (H₂O)₃. In the atmosphere at 0 km altitude within the temperature range of 280.0–320.0 K, the reaction with H₂O is dominant, compared with the reaction without a catalyst, with an effective rate constant 2–3 orders of magnitude larger. In addition, at 0 km, it is worth mentioning that the relevance of the HO₂ + SO₂ → HOSO + ³O₂ reaction with H₂O depends heavily on its ability to compete with the primary loss mechanism of HO₂ radicals (such as the HO₂ + HO₂ and HO₂ + NO₃ reactions) and SO₂ (such as the SO₂ + HO reaction). The calculated results show that the HO₂ + SO₂ → HOSO + ³O₂ reaction with H₂O cannot be neglected in the primary loss mechanism of the HO₂ radical and SO₂. The calculated results also show that for the formation of HOSO and ³O₂, the contribution of H₂O decreases from 99.98% to 27.27% with an increase in altitude from 0 km to 15 km, due to the lower relative concentration of water. With the altitude increase, the HO₂ + SO₂ → HOSO + ³O₂ reaction with H₂O cannot compete with the primary loss mechanism of HO₂ radicals. The present results provide new insight into (H₂O)_n (n = 1–3) catalysts, showing that they not only affect energy barriers, but also have an influence on loss mechanisms. The present findings should have broad implications in computational chemistry and atmospheric chemistry.

The HO₂ + SO₂ → HOSO + ³O₂ reaction without and with (H₂O)_n (n = 1–3) have been investigated using CCSD(T)/CBS//M06-2X/aug-cc-pVTZ methods, and canonical variational transition state theory with small curvature tunneling.     

Experimental and computational preference for phosphine regioselectivity and stereoselective tripodal rotation in HOs3(CO)8(PPh3)2(μ-1,2-N,C-η1,κ1-C7H4NS)

The site preference for ligand substitution in the benzothiazolate-bridged cluster HOs₃(CO)₁₀(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (1) has been investigated using PPh₃. 1 reacts with PPh₃ in the presence of Me₃NO to afford the mono- and bisphosphine substituted clusters HOs₃(CO)₉(PPh₃)(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (2) and HOs₃(CO)₈(PPh₃)₂(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (3), respectively. 2 exists as a pair of non-interconverting isomers where the PPh₃ ligand is situated at one of the equatorial sites syn to the edge-bridging hydride that shares a common Os–Os bond with the metalated heterocycle. The solid-state structure of the major isomer establishes the PPh₃ regiochemistry at the N-substituted osmium center. DFT calculations confirm the thermodynamic preference for this particular isomer relative to the minor isomer whose phosphine ligand is located at the adjacent C-metalated osmium center. 2 also reacts with PPh₃ to give 3. The locus of the second substitution occurs at one of the two equatorial sites at the Os(CO)₄ moiety in 2 and gives rise to a pair of fluxional stereoisomers where the new phosphine ligand is scrambled between the two equatorial sites at the Os(CO)₃P moiety. The molecular structure of the major isomer has been determined by X-ray diffraction analysis and found to represent the lowest energy structure of the different stereoisomers computed for HOs₃(CO)₈(PPh₃)₂(μ-1,2-N,C-η¹,κ¹-C₇H₄NS). The fluxional behavior displayed by 3 has been examined by VT NMR spectroscopy, and DFT calculations provide evidence for stereoselective tripodal rotation at the Os(CO)₃P moiety that serves to equilibrate the second phosphine between the two available equatorial sites.

The site preference for PPh₃ substitution in HOs₃(CO)₁₀(PPh₃)₂(μ-1,2-N,C-η¹,κ¹-C₇H₄NS) (1) has been investigated.     

Catalytic effect of (H2O)n (n = 1–3) on the HO2 + NH2 → NH3 + 3O2 reaction under tropospheric conditions

The effects of (H₂O)_n (n = 1–3) clusters on the HO₂ + NH₂ → NH₃ + ³O₂ reaction have been investigated by employing high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods, and canonical variational transition (CVT) state theory with small curvature tunneling (SCT) correction. The calculated results show that two kinds of reaction, HO₂⋯(H₂O)_n (n = 1–3) + NH₂ and H₂N⋯(H₂O)_n (n = 1–3) + HO₂, are involved in the (H₂O)_n (n = 1–3) catalyzed HO₂ + NH₂ → NH₃ + ³O₂ reaction. Due to the fact that HO₂⋯(H₂O)_n (n = 1–3) complexes have much larger stabilization energies and much higher concentrations than the corresponding complexes of H₂N⋯(H₂O)_n (n = 1–3), the atmospheric relevance of the former reaction is more obvious with its effective rate constant of about 1–11 orders of magnitude faster than the corresponding latter reaction at 298 K. Meanwhile, due to the effective rate constant of the H₂O⋯HO₂ + NH₂ reaction being respectively larger by 5–6 and 6–7 orders of magnitude than the corresponding reactions of HO₂⋯(H₂O)₂ + NH₂ and HO₂⋯(H₂O)₃ + NH₂, the catalytic effect of (H₂O)_n (n = 1–3) is mainly taken from the contribution of the water monomer. In addition, the enhancement factor of the water monomer is 10.06–13.30% within the temperature range of 275–320 K, which shows that at whole calculated temperatures, a positive water effect is obvious under atmospheric conditions.

The catalytic effect of (H₂O)_n (n = 1−3) on the HO₂ + NH₂ → NH₃ + ³O₂ is mainly taken from the contribution of a single water vapor.     

The unique sandwich K6Be2B6H6 cluster with a real borozene B6H6 core

Theoretical evidence is reported for a boron-based K₆Be₂B₆H₆ sandwich cluster, showing a perfectly D_6h B₆H₆ ring, being capped by two tetrahedral K₃Be ligands. Due to the comfortable charge transfer, the sandwich is viable in [K₃Be]³⁺[B₆H₆]⁶⁻[BeK₃]³⁺ ionic complex in nature. The [B₆H₆]⁶⁻ core with 6π aromaticity vividly imitates the benzene (C₆H₆), occurring as a real borozene. In contrast, the tetrahedral [K₃Be]³⁺ ligand is 2σ three-dimensional aromatic, acting as the simple superatom. Thus, this complex possesses a collectively three-fold 2σ/6π/2σ aromaticity. The interlaminar interaction is governed by the robust electrostatic attraction. The unique chemical bonding gives rise to interesting dynamic fluxionality.

The fascinating sandwich K₆Be₂B₆H₆ cluster with a real borozene ring, being stabilized collectively by three-fold 2σ/6π/2σ aromaticity.     

Cation dynamics by 1H and 13C MAS NMR in hybrid organic–inorganic (CH3CH2NH3)2CuCl4

To understand the dynamics of the cation in layered perovskite-type (CH₃CH₂NH₃)₂CuCl₄, the temperature-dependent chemical shifts and spin–lattice relaxation times T_1ρ in the rotating frame have been measured using ¹H magic angle spinning nuclear magnetic resonance (MAS NMR) and ¹³C cross-polarization (CP)/MAS NMR techniques. Each proton and carbon in the (CH₃CH₂NH₃)⁺ cation is distinguished in MAS NMR spectra. The Bloembergen–Purcell–Pound (BPP) curves for ¹H T_1ρ in CH₃CH₂ and NH₃, and for the ¹³C T_1ρ in CH₃ and CH₂ are revealed to have minima at low temperatures. This implies that the curves represent the CH₃ and NH₃⁺ rotational motions. The amplitude of the cationic motion is enhanced at the C-end, that is, the N-end of the organic cation is fixed to the inorganic layer through N–H⋯Cl hydrogen bonds, and T_1ρ becomes short with larger-amplitude molecular motions.

To understand the dynamics of the cation in layered perovskite-type (CH₃CH₂NH₃)₂CuCl₄, the temperature-dependent chemical shifts and spin–lattice relaxation times T_1ρ have been measured using ¹H MAS NMR and ¹³C CP/MAS NMR techniques.     

Structural and thermal properties of Na2Mn(SO4)2·4H2O and Na2Ni(SO4)2·10H2O

The title compounds were prepared via a wet chemistry route and their crystal structures were determined from single crystal X-ray diffraction data. Na₂Mn(SO₄)₂·4H₂O crystallizes with a monoclinic symmetry, space group P2₁/c, with a = 5.5415(2), b = 8.3447(3), c = 11.2281(3) Å, β = 100.172(1)°, V = 511.05(3) ų and Z = 2. Na₂Ni(SO₄)₂·10H₂O also crystallizes with a monoclinic symmetry, space group P2₁/c, with a = 12.5050(8), b = 6.4812(4), c = 10.0210(6) Å, β = 106.138(2)°, V = 780.17(8) ų and Z = 2. Na₂Mn(SO₄)₂·4H₂O is a new member of the blödite family of compounds, whereas Na₂Ni(SO₄)₂·10H₂O is isostructural with Na₂Mg(SO₄)₂·10H₂O. The structure of Na₂Mn(SO₄)₂·4H₂O is built up of [Mn(SO₄)₂(H₂O)₄]²⁻ building blocks connected through moderate O–H⋯O hydrogen bonds with the sodium atoms occupying the large tunnels along the a axis and the manganese atom lying on an inversion center, whereas the structure of Na₂Ni(SO₄)₂·10H₂O is built up of [Ni(H₂O)₆]²⁺ and [Na₂(SO₄)₂(H₂O)₄]²⁻ layers. These layers which are parallel to the (100) plane are interconnected through moderate O–H⋯O hydrogen bonds. The thermal gravimetric- and the powder X-ray diffraction-analyzes showed that only the nickel phase was almost pure. At a temperature above 300 °C, all the water molecules evaporated and a structural phase transition from P2₁/c-Na₂Ni(SO₄)₂·10H₂O to C2/c-Na₂Ni(SO₄)₂ was observed. C2/c-Na₂Ni(SO₄)₂ is thermally more stable than Na₂Fe(SO₄)₂ and therefore it would be suitable as the positive electrode for sodium ion batteries if a stable electrolyte at high voltage is developed.

Two compounds were prepared via a supersaturation method. Their crystal structures were solved and compared to Na₂M(SO₄)₂·nH₂O (M = Mn, Ni and n = 0, 1, 2, 3, 4, 5, 6, 10, 16). Furthermore, phase transitions as a function of temperature were observed.     

Metal ion size profoundly affects H3glyox chelate chemistry

The bisoxine hexadentate chelating ligand, H₃glyox was investigated for its affinity for Mn²⁺, Cu²⁺ and Lu³⁺ ions; all three metal ions are relevant with applications in nuclear medicine and medicinal inorganic chemistry. The aqueous coordination chemistry and thermodynamic stability of all three metal complexes were thoroughly investigated by detailed DFT structure calculations and stability constant determination, by employing UV in-batch spectrophotometric titrations, giving pM values (pM = −log[Mⁿ⁺]_free when [Mⁿ⁺] = 1 μM, [L] = 10 μM at pH 7.4 and 25 °C) – pCu (25.2) > pLu (18.1) > pMn (12.0). DFT calculated structures revealed different geometries and coordination preferences of the three metal ions; notable was an inner sphere water molecule in the Mn²⁺ complex. H₃glyox labels [^52gMn]Mn²⁺, [⁶⁴Cu]Cu²⁺ and [¹⁷⁷Lu]Lu³⁺ at ambient conditions with apparent molar activities of 40 MBq μmol⁻¹, 500 MBq μmol⁻¹ and 25 GBq μmol⁻¹, respectively. Collectively, these initial investigations provide insight into the effects of metal ion size and charge on the chelation with the hexadentate H₃glyox and indicate that further investigations of the Mn²⁺–H₃glyox complex in ^52g/55Mn-based bimodal imaging might be worthwhile.

The bisoxine hexadentate chelating ligand, H₃glyox was investigated for its affinity for Mn²⁺, Cu²⁺ and Lu³⁺ ions; all three metal ions are relevant with applications in nuclear medicine and medicinal inorganic chemistry.     

Nitrogen versus carbon in planar pentacoordinate environments supported by Be5Hn rings

NBe₅H_nⁿ⁻³ (n = 0–5) (0A–5A) species with a novel planar pentacoordinate nitrogen (ppN) were designed by the isoelectronic substitution of the C atom in planar pentacoordinate carbon (ppC) species CBe₅H_nⁿ⁻⁴ (n = 0–5) with an N atom. The highly flexible H atoms found in ppC species CBe₅H₂²⁻ and CBe₅H₃⁻ were fixed upon the nitrogen substitution, as mirrored by the non-flexible H atoms in their ppN analogues NBe₅H₂⁻ (2A) and NBe₅H₃ (3A). Moreover, the N atom was found to fit the H-surrounded Be₅ rings better than the C atom because the ppC species CBe₅H₄ and CBe₅H₅⁺ adopted non-planar structures due to size-mismatch between the C atom and the H-surrounded Be₅ ring, but their ppN analogues NBe₅H₄⁺ (4A) and NBe₅H₅²⁺ (5A) adopted perfect planar structures. The electronic structure analyses revealed that the N atoms in 0A–5A were involved in four doubly occupied orbitals, including three six-center two-electron (6c-2e) σ bonds and one 6c-2e π bond. Therefore, these ppN species not only obey the octet rule, but also possess the interesting σ and π double aromaticity, which contributes to the stabilization. Consequently, 2A, 4A, and 5A are charged kinetically viable global energy minima, and are suitable for the gas phase generation and spectroscopic characterization.

Nitrogen is a better fit for Be₅H_n rings, both geometrically and electronically, than carbon, leading to the viable planar pentacoordinate nitrogen species.     

Mixed Tb/Dy coordination ladders based on tetra(carboxymethyl)thiacalix[4]arene: a new avenue towards luminescent molecular nanomagnets

The macrocyclic ligand calix[4]arene (L1) and its sulphur-containing analogue thia[4]calixarene (L2) are promising precursors for functional molecular materials as they offer rational functionalization with various organic groups. Here, we present the first example of lanthanide-based coordination polymers built from the macrocyclic thiacalix[4]arene backbone bearing four carboxylic moieties, namely, ligand H₄L3. The combination of H₄L3 with the Tb³⁺ and Dy³⁺ cations led to the formation of 1D ladder-type coordination polymers with the formula [Ln^IIIHL3DMF₃]·(DMF) (where DMF = dimethylformamide and Ln = Tb or Dy, denoted as HL3–Tb and HL3–Dy), which resulted from the coordination of the lanthanide cations with the partially deprotonated ligand HL3³⁻ that behaved as a T-shape connector. The coordination sphere around the metal was completed by the coordinated DMF solvent molecules. By combining both Tb³⁺ and Dy³⁺ cations, isostructural heterobimetallic solid solutions HL3–Tb_1−xDy_x were also prepared. HL3–Tb and HL3–Dy showed visible light photoluminescence originating from the f–f electronic transitions of pale green emissive Tb³⁺ and pale yellow emissive Dy³⁺ with efficient sensitization by the functionalized thia[4]calixarene ligand HL3. In the HL3–Tb_1−xDy_x solid solutions, the Tb/Dy ratio governed both the emission colour as well as the emission quantum yield, which reached even 28% at room temperature for HL3–Tb. Moreover, HL3–Dy exhibited a slow magnetic relaxation effect related to the magnetic anisotropy of the dodecahedral Dy³⁺ complexes, which were well isolated in the crystal lattice by expanded organic spacers.

The single crystals of the two isostructural Tb³⁺- and Dy³⁺-based coordination polymers (HL3–Tb and HL3–Dy) were structurally characterized, and their photophysical properties were investigated, together with their corresponding solid solutions.     

Naphthalimide based smart sensor for CN−/Fe3+ and H2S. Synthesis and application in RAW264.7 cells and zebrafish imaging

Achieving selective detection of target analytes in aqueous media continues to be an arduous proposition. Herein, we report the conceptualization and synthesis of a novel tailor-fit molecular probe R based on 1,8-naphthalimide which acts as a trifunctional molecular sensor for CN⁻, Fe³⁺ and H₂S. R shows colorimetric and fluorometric “on–off” relay recognition for CN⁻ (red colour and orange emission) and Fe³⁺ (no colour and no emission) in 5% H₂O + DMSO medium which is experimentally ascertained to be a tandem deprotonation–protonation process and is supported by ¹H-NMR titration. Among all RSS (Reactive Sulphur Species), R shows selectivity for H₂S through red colouration. Other coexistent anions, cations and RSS cause no discernible perturbation to the detection process. The detection of H₂S is attributed to a chemodosimetric reduction of the nitro to amino group as evidenced by a potentiometric titration assay. The experimental observations are well supported by DFT theoretical calculation. The K_a for CN⁻/Fe³⁺ are 1.4 × 10⁴ M⁻¹, 6.07 × 10⁴ M⁻¹ respectively and photochemical yield of R + CN⁻ is 0.86. Limit of detections for CN⁻, Fe³⁺ and H₂S are 17.5 nM, 8.69 μM and 8.1 μM respectively. Receptor R is effective for real time applications, bio-compatible and has been successfully employed for confocal fluorescence imaging of RAW264.7 cell and zebrafish.

Probe R designed as tailor-fit triple action smart chemosensor for the sequential detection of CN⁻ and Fe³⁺via colorimetric and fluorometric ‘on–off’ method and H₂S through colorimetric method in semi-aqueous conditions.