Three-Dimensional Perovskite Phase Transition Materials with Switchable Second Harmonic Generation Properties Introduced by Homochiral (1S,4S)-2,5-Diazabicyclo[2.2.1]-heptane.

Switchable second harmonic generation (SHG) materials have potential applications in information storage, signal processing, and so on because they can switch between SHG-on and SHG-off states. In this work, we designed and synthesized three organic-inorganic hybrid Rb halide three-dimensional (3D) perovskite materials [1S,4S 2,5-2.2.1-H2dabch]RbX3·0.5H2O (X = Cl, 1; Br, 2; I, 3) based on the chiral 1S,4S-2,5-diazabicyclo[2.2.1]heptane (1S,4S-2,5-2.2.1-dabch). The selection of homochiral organic cations ensures that the compounds 1∼3 crystallize in the noncentrosymmetric and chiral space group P212121, which further leads to reversible SHG responses of the three compounds. Through differential scanning calorimetry (DSC) and dielectric measurements, it revealed that the phase transition point of the compounds 1∼3 increased with RbCl, RbBr, and RbI. This is because the hydrogen interaction H···X between the inorganic framework [RbX3]n and the organic cation [1S,4S-2,5-2.2.1-H2dabch]2+ is increased with the order of I > Br > Cl. This study can provide an effective molecular design strategy for the exploration and construction of temperature-tunable SHG switching materials.

Two metal-free perovskite molecules with different 3D frameworks show reversible phase transition, dielectric anomaly and SHG effect.

Three-dimensional (3D) hybrid organic-inorganic perovskites (HOIPs) have attracted tremendous research interest due to their unique structure and promising applications. However, research on the design, synthesis and properties of this kind of metal-free crystalline material is still in the exploratory stage. Herein, two 3D perovskite molecules [1,4-3.2.2-dabcn]NH4Br3 (1) and [1,4-3.2.2-dabcn]NH4I3·0.5H2O (2) were obtained by reacting 1,4-diazabicyclo[3.2.2]nonane (1,4-3.2.2-dabcn) with NH4X (X = Br and I) in the corresponding concentrated halogen acids. The single X-ray diffraction results demonstrated that the inorganic framework structures in compounds 1 and 2 constructed with NH4Br and NH4I are completely different, caused by the radius of the bromide ion being smaller than that of the iodide ion. The 3D framework of compound 1 is constructed with a coplanar dimer [(NH4)2Br6]2- as the basic building unit, leading to the expanded 3D perovskite framework structure with a larger cavity to accommodate the 1,4-3.2.2-dabcn molecule. Nevertheless, compound 2 adopts a familiar 3D crystal framework structure with corner-sharing [(NH4)I6] octahedra, where the [1,4-3.2.2-dabcn] cations and water solvent molecule are confined in the cavities enclosed by the octahedra. Notably, both compounds exhibit reversible phase transition, dielectric anomaly and the second harmonic generation (SHG) effect. From the perspective of molecular design, this work is of great significance to guide the construction of new 3D metal-free perovskite molecular materials with reversible properties.

Two host-guest grown ether supramolecules show switchable phase transition, dielectric and second-harmonic generation effect.

The excellent properties of host-guest crown ether inclusions in phase transition, dielectric and second-order nonlinear optical properties have attracted much attention. In this paper, we successfully designed and prepared two novel host-guest crown ether supramolecules [(DFBA)(15-crown-5)]X (X = ClO4-, 1; ReO4-, 2) by reactions of 2,6-difluorobenzylamine (DFBA) with 1,4,10,13-pentaoxacyclopentadecane (15-crown-5) in HClO4, or HReO4 aqueous solution. By the introduction of difluoro-substituted benzylamine as a guest cation, the phase transition temperatures are greatly increased to 377 K for 1 and 391 K for 2. More importantly, the space group of 1 has changed from centrosymmetric (CS) P2/c to the non-centrosymmetric (NCS) Pca21 in 2 when substituting perchlorate (ClO4-) with the larger and heavier perrhenate (ReO4-), which leads to 2 showing a switchable and stable second-harmonic generation (SHG) effect. According to the principle of momentum matching between a cation and anion, the perrhenate group increases the energy barrier of the molecular thermal motion, which not only significantly increases the phase transition temperature of 2 but also causes it to be frozen and crystallized in a NCS space group at room temperature. This research demonstrates that a polar molecule can adjust the suitability of anions and cations inside the crystal by practical chemical means.

Two 3D Rubidium Halide Organic-Inorganic Hybrid Perovskite Ferroelectrics Templated by Quasi-Spherical Organic Amine 1,4-Diazabicyclo[3.2.2]nonane.

The emergence of (CH3 NH3 )PbI3 has brought the development of three-dimensional (3D) organic-inorganic hybrid perovskite (OIHP) structures with ABX3 type to a higher level; however, most 3D frameworks are constructed by corner-sharing of BX6 octahedra. Herein, we substituted the spherical molecule 1,4-diazabicyclo[2.2.2]octane (2.2.2-dabco) with 1,4-diazabicyclo[3.2.2]nonane (1,4-3.2.2-dabcn) as a template to react with RbX (X=Br, I) in the corresponding HX acids under the consideration of reducing the molecular symmetry. Two 3D OIHP compounds [1,4-3.2.2-H2 dabcn]RbI3 ⋅H2 O (1) and [1,4-3.2.2-H2 dabcn]RbBr3 (2) crystallized in non-centrosymmetric point group mm2 before the phase transition point were isolated. Among them, the 3D inorganic framework of 1 is constructed by sharing the corner of [RbI6 ] octahedra, while that of 2 is constructed by sharing the corner and face of [RbBr6 ] octahedra to acquire large cavities to accommodate the organic amine cation [1,4-3.2.2-H2 dabcn]2+ ; this 3D framework type is unprecedented in the OIHPs. As expected, compounds 1 and 2 exhibit reversible phase transition, dielectric and second harmonic generation (SHG) and ferroelectric properties, in which the phase transition temperature of 2 at 374 K is much higher than compound 1 at 280 K.

The Role of Fluorine-Substituted Positions on the Phase Transition in Organic-Inorganic Hybrid Perovskite Compounds.

Although research on organic-inorganic hybrid perovskites (OIHPs) has grown exponentially in the past two decades, the high phase transition temperature of OIHP materials is still one of the insurmountable difficulties. Herein, a series of A2BX4 type OIHP materials [(2,n-DFBA)2PbCl4] (n = 3, for 1; n = 4, for 2; n = 5, for 3; n = 6, for 4) have been prepared by reactions of double-substituted difluorobenzylamine (difluorobenzylamine = DFBA) with lead chloride in concentrated HCl aqueous solution. It was found the OIHP compounds 1-3 proceed a switchable phase transition with phase transition temperatures (Tc) at 449 K (1), 462 K (2) and 500 K (3), higher than that of the parent compound [(BA)2PbCl4] (BA = benzylammonium) at 438 K, but compound 4 exhibits no phase transition. A crystal structure analysis elucidated that the organic template ligands DFBA lead in the inorganic part in compounds 1-3 to a two-dimensional (2D) perovskite structure, while that in compound 4 leads to a one-dimensional (1D) chain structure. The different double-substituted positions of fluorine atoms on benzylamine have important influences on the phase transition in compounds 1-4.

Tin based organic-inorganic hybrid semiconductors with reversible phase transition and dielectric anomaly.

Organic-inorganic hybrid materials with perovskite structure have recently attracted tremendous interest due to their structural tunability and rich functional properties, such as phase transition and photoelectric properties. Within this context, two discrete tin-based organic-inorganic hybrid compounds [(FMBA)2SnCl6] (1) and [(FMBA)2SnBr6] (2) were prepared by the reaction of 3-fluoro-N-methylbenzylamine (FMBA) with SnX4 (X = Cl, Br) in the corresponding concentrated halogen acids HX. Differential scanning calorimetry (DSC) and dielectric measurements showed that both compounds underwent reversible phase transition and dielectric anomaly at a phase transition point above 400 K. Crystal structure analyses revealed that the phase transition mainly originated from the order and disorder of a fluorine-substituted organic amine structure at low and high temperatures. Meanwhile, both compounds showed a semiconducting property with optical bandgaps of 4.24 eV for 1 and 2.58 eV for 2. This finding of two Sn(iv)-based metal halides with prominent phase transition and semiconducting behaviors will expand an executable pathway for designing multifunctional perovskite-type switchable materials.

Designed self-assembled hybrid Au@CdS core-shell nanoparticles with negative charge and their application as highly selective biosensors.

A novel and general strategy for the synthesis of a monodispersed Au@CdS core-shell structure with uniform morphology and size through a self-assembly process is proposed here. The obtained negatively charged Au@CdS hybrid core-shell nanoparticles (NPs) are highly selective to dopamine (DA), in the presence of oxidation of ascorbic acid (AA) and uric acid (UA), based on electrostatic interaction. The fabricated biosensor shows a wide linear range from 0.002 to 800 µmol L-1, with a lower detection limit of 0.55 nmol L-1 (n = 5, S/N = 3), revealing the high-sensitivity properties. Electrostatic charge plays an important role in the selective electrocatalytic activity of Au@CdS hybrid core-shell nanoparticles, that is the formation of an electrostatic system between the negatively charged Au@CdS hybrid core-shell NPs and the DA cation. The modified electrode is used to achieve the real-time quantitative detection of DA for biological applications, and satisfactory results are obtained. Due to the advantages of the biosensor, its selectivity, sensitivity and stability, it will have a bright future in the field of medical diagnosis.

Fabrication of metal-organic single crystalline nanowires and reduced graphene oxide enhancement for an ultrasensitive electrochemical biosensor.

A novel strategy is first presented here to design and construct a good selective and highly sensitive dopamine (DA) biosensor based on single-crystalline CuPc nanowires with a reduced graphene oxide-Nafion film (rGON/CuPcNWs). Metal-organic semiconductor single-crystalline CuPc nanowires with excellent electronic properties and large surface-to-volume ratios were prepared using a physical vapor transport technique and modified onto a glassy carbon electrode (GCE), and exhibited high electrocatalytic activity for DA detection by immobilizing it onto a GCE with a film of the rGON composite. The introduction of a rGO-Nafion film can significantly improve the electrochemical signal of the CuPcNWs. The relevant detection limit toward dopamine is 0.3 nM with a wide linear range from 0.001 µM to 200 µM. The results of the demonstrated biosensor could provide important enlightenment for the design of more sensitive electrochemical biosensors.

4,10-Bis(pyridin-2-ylmeth-yl)-1,7-dithia-4,10-diazo-niacyclo-dodecane bis(perchlorate).

The asymmetric unit of the title compound C(20)H(30)N(4)S(2) (+). 2ClO(4) (-) comprises one macrocyclic cation and two perchlorate anions. In the cation, one of the protonated H atoms bound to the amide N atom is involved in an intra-molecular N-H⋯N hydrogen bond. The O atoms in the two perchlorate anions are disordered over two sets of sites with occupancy ratios of 0.65 (3):0.35 (3) and 0.640 (15):0.360 (15).

Two W/Cu/S clusters: tetraethylammonium bromidodi-µ2-sulfido-sulfido[tris(3,5-dimethylpyrazol-1-yl)borato]copper(I)tungsten(VI) and tetraethylammonium dibromido-µ3-sulfido-di-µ2-sulfido-[tris(3,5-dimethylpyrazol-1-yl)borato]dicopper(I)tungsten(VI).

The reaction of (Et(4)N)[Tp*WS(3)] [Tp* = hydrogen tris(3,5-dimethylpyrazol-1-yl)borate] with one or two equivalents of CuBr afforded the [1 + 1] and [1 + 2] addition products (Et(4)N)[Tp*WS(µ-S)(2)(CuBr)] {or (C(8)H(20)N)[CuWBr(C(15)H(22)BN(6))S(3)], (I)} and (Et(4)N)[Tp*W(µ(3)-S)(µ-S)(2)(CuBr)(2)] {or (C(8)H(20)N)[Cu(2)WBr(2)(C(15)H(22)BN(6))S(3)], (II)}. The anion of (I) contains a [W(µ-S)(2)Cu] core formed by the addition of one CuBr unit to the [Tp*WS(3)] species. The anion of (II) has a butterfly-shaped [W(µ(3)-S)(µ-S)(2)Cu(2)] core formed by the addition of two CuBr units to the [Tp*WS(3)] species. The [Tp*WS(3)] sections of each complex exhibit approximate C(3v) point symmetry and have closely comparable geometry. In (II), both the anion and cation lie on a crystallographic mirror plane. The structure of (I) is noncentrosymmetric and polar.

Tetra-ethyl-ammonium dicyanidobis(ethane-1,2-dithiol-ato)tetra-µ(3)-sulfido-dimolybdenum(V)dicopper(I).

The title compound, (C(8)H(20)N)(2)[Cu(2)Mo(2)(C(2)H(4)S(2))(2)(CN)(2)S(4)], is a sulfide-bridged tetranuclear complex in which the complex anion comprises one [(edt)(2)Mo(2)S(2)(µ-S)(2)](2-) unit (edt = ethanedithiol-ate) and two CuCN units joined through six Cu-µ(3)-S bonds, thus forming a cubane-like [Mo(2)S(4)Cu(2)] core. There are two independent cation-anion complex entities in the asymmetric unit. Bond distances are normal for this type of complex [ranges: Mo-S = 2.193 (2)-2.390 (2); Cu-S = 2.266 (2)-2.470 (2); Cu-C = 1.899 (7)-1.911 (9) Å]. One of the thiol-ato C atoms is disordered over two sites in a 0.52 (3):0.48 (3) ratio.

Bis[µ(2)-bis-(diphenyl-phosphino)methane]bis-(µ(2)-ethane-1,2-dithiol-ato)-µ(4)-sulfido-µ(2)-sulfido-disulfidodimolybdenum(V)disilver(I) dimethyl-formamide tris-olvate.

Treatment of [Et(4)N](2)[(edt)(2)Mo(2)S(2)(µ-S)(2)] (edt = ethane-dithio-l-ate) with two equivalents of Ag(CH(3)CN)(4)ClO(4) in the presence of bis-(diphenyl-phosphino)methane (dppm) ligand gives rise to the title tetra-nuclear cluster, [Ag(2)Mo(2)(C(2)H(4)S(2))(2)S(4)(C(25)H(22)P(2))(2)]·3C(3)H(7)NO. The complex mol-ecule and one of the dimethyl-formamide (DMF) solvent mol-ecules occupy special positions on a mirror plane. The mol-ecular structure of the complex may be visualized as being built of [Mo(2)S(2)(µ-S)(2)(edt)(2)](2-) dianions and [Ag(2)(dppm)(2)](2+) dications connected by two Ag-µ-S(edt) and two Ag-µ(4)-S bonds.

Di-µ-sulfato-bis-{[bis-(3,5-dimethyl-pyrazol-1-yl)methane]copper(II)}.

The mol-ecule of the title compound, [Cu(2)(SO(4))(2)(C(11)H(16)N(4))(2)], sits on a center of symmetry. The Cu(II) atom has a distorted trigonal-bipyramidal coordination geometry comprising three O atoms of the two symmetry-related SO(4) (2-) anions and two N atoms from one bis-(3,5-dimethyl-pyrazol-1-yl)methane ligand.

catena-Poly[[(nitrato-κO,O')silver(I)]-µ-1,2-bis-(diphenyl-phosphino)ethane-κP:P'].

In the title chain compound, [Ag(NO(3))(C(26)H(24)P(2))](n), the bis-(diphenyl-phosphino)ethane (dppe) units link the Ag(+) ions into chains along [001]. A nitrate anion is coordinated to the Ag atom. There is a centre of symmetry at the mid-point of the ethane C-C bond and a twofold rotation axis passes through the Ag, N and terminal O atoms. Each Ag atom is four-coordinated in a distorted tetra-hedral geometry by two O atoms of the nitrate anion and two P atoms of dppe ligands. The two aromatic rings are oriented at a dihedral angle of 73.77 (3)°.

C-H...pi, pi-pi and C-H...Cl interactions in chloro-substituted Schiff bases and 4-chloro-N-[4-(dimethylamino)benzylidene]aniline.

Molecular packing analyses were carried out on 15 crystal data sets of chloro-substituted Schiff bases, including that of the title compound, C15H15ClN2. C-H...pi and pi-pi interactions play a major role in the molecular self-assembly in the crystal. The former interactions favor molecules assembling into a screw, with a non-centrosymmetric crystal structure. When the molecular dipole is small, pi-pi interactions favor a parallel, but not usually antiparallel, mode of packing. Weak C-H...X hydrogen bonds (X = Cl or Br) and X...X interactions seem to be a secondary driving force in packing. The title molecule takes the trans form and the two benzene rings are twisted around the central linkage in opposite directions. In the crystal structure, molecules interact through C-H...pi and pi-pi interactions, forming a 'dimer' and further forming double chains along [001]. The double chains are extended along [101] through C-H...Cl hydrogen bonds, forming double layers in (010). In the third direction, there are only ordinary, weaker, van der Waals interactions, which explains the crystal habit (i.e. thin plate).