Wide spectral range nonlinear optical crystals of one-dimensional coordination solids [Et4N][Cd(SCN)3] and [Et4N][Cd(SeCN)3] and the general design criteria for [R4N][Cd(XCN)3] (Where R = Alkyl and X = S, Se, Te) as NLO crystals

Targeted regulation and optimization of multifunctional phase transition materials by novel void occupancy engineering

As an innovative form of stimulus-response materials, organic-inorganic hybrid phase transition materials have become a wonderful contender in the field of functional electronic equipment due to their versatile structure, intensive functions and straightforward preparation. However, the targeted regulation and optimization of the electrical/optical response, along with the establishment of regular structure-performance relationships, pose significant challenges in meeting the diverse demands of practical applications over an extended period. Herein, we conducted a systematic investigation into the role of lattice void occupancy in regulating phase transition temperature (Tp) and related optical/electrical bistability. By taking hybrid material [TMEA][Cd(SCN)3] featuring a flexible ammonium cation [TMEA]+ (TMEA = ethyltrimethylammonium) as the prototype, we successfully synthesized three phase transition materials, namely [DEDMA][Cd(SCN)3], [TEMA][Cd(SCN)3] and [TEA][Cd(SCN)3] (DEDMA = diethyldimethylammonium, TEMA = triethylmethylammonium, and TEA = tetraethylammonium), and the excellent regulation of the physical properties of these compounds was achieved through subtle engineering of void occupancy. More strikingly, [TEA][Cd(SCN)3] exhibits remarkable bistable properties in terms of dielectric and nonlinear optical responses (with second-harmonic generation intensity reaching 2.5 times that of KDP). This work provides a feasible avenue to reasonably customise organic-inorganic hybrid phase transition materials and finely adjust their intriguing functionalities.

Synthesis, crystal structure and luminescence properties of one inorganic-organic hybrid compound [FTMA]2[Co(NCS)4] (FTMA = ferrocenylmethyltrimethylammonium cation)

A new inorganic-organic hybrid compound [FTMA](2)[Co(NCS)(4)] (FTMA = ferrocenylmethyltrimethylammonium cation) has been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Co(II) atom has a distorted tetrahedral environment with four N atoms of four NCS(-) anions. In the solid state there are C-H⋯π interactions between adjacent ferrocenyl cations, which generate one-dimensional (1-D) supramolecular chain, and C-H⋯S hydrogen bonds between [FTMA](+) cations and cobalt thiocyanate anions. The title compound shows strong purple fluorescence emission in the solid state at room temperature.

Synthesis, crystal structure and luminescent properties of one new inorganic-organic hybrid compound [O2NBzQL]4[Cd(SCN)4(NCS)2] (O2NBzQL=1-(4'-NO2-benzyl)quinolinium cation)

A new inorganic-organic hybrid compound [O2NBzQL]4[Cd(SCN)4(NCS)2] (O2NBzQL=1-(4'-NO2-benzyl)quinolinium cation) has been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Cd(II) atom has an distorted octahedral environment with an N4S2 donor set. In solid state there are three types of face-to-face π-π interactions between adjacent cations and multiform C-H⋯S and C-H⋯N hydrogen bonds between [O2NBzQL]+ cations and cadmium thiocyanate anions. The luminescent properties of the title compound were both investigated in H2O solution and in solid state at room temperature, respectively.

Synthesis of a series of 4-pyridyl-1,2,4-triazole-containing cadmium(ii) luminescent complexes

Using two 4-substitued triazole ligands, 4-(pyrid-2-yl)-1,2,4-triazole (L(1)) and 4-(pyrid-3-yl)-1,2,4-triazole (L(2)), a series of novel triazole-cadmium(II) complexes varying from zero- to three-dimensional have been prepared and their crystal structures determined via single-crystal X-ray diffraction. [Cd(2)(micro(2)-L(1))(3)(L(1))(2)(NO(3))(mu(2)-NO(3))(H(2)O)(2)](NO(3))(2).1.75H(2)O (1) is a binuclear complex containing bidendate, monodedate and free nitrate anions. When the bridging anions SCN(-) and dca (dca = N(CN)(2)(-)) were added to the reaction system of 1, one-dimensional (1D) [Cd(L(1))(2)(NCS)(2)](n) (2) and two-dimensional (2D) [Cd(L(1))(2)(dca)(2)](n) (3) were isolated, respectively. When L(2) instead of L(1) was used, [Cd(L(2))(2)(NCS)(2)(H(2)O)(2)] (4) and 1D [Cd(L(2))(2)(dca)(2)](n) (5) were obtained. When the ratio of Cd to L(2) was changed from 1:2 to 1:1 in the reaction system of 5, three-dimensional (3D) {[Cd(3)(micro(2)-L(2))(3)(dca)(6)].0.75H(2)O}(n) (6) with 1D microporous channels along the a direction was isolated. Further investigations on other Cd(ii) salts and the L(2) ligand in a Cd to L(2) ratio of 1:1, an unexpected complex [Cd(mu(2)-L(2))(mu(3)-SO(4))(H(2)O)](n) (7) with a 3D open framework was obtained. All of the complexes exhibit strong blue fluorescence emission bands in the solid state at ambient temperature, of which the excitation and emission maxima are red-shifted to longer wavelength as compared to those in water. Powder X-ray diffraction and thermal studies were used to investigate the bulk nature of the 3D coordination polymers 6 and 7.

Novel Triazole-Bridged Cadmium Coordination Polymers Varying from Zero- to Three-Dimensionality

Cadmium salts with different triazole ligands have led to a series of novel triazole-cadmium compounds varying from zero- to three-dimensionality. [Cd(2)(deatrz)(2)(H(2)O)Br(4)] (1) (deatrz = 3,5-diethyl-4-amino-1,2,4-triazole) is a zero-dimensional complex which uses a triazole ligand together with micro-OH(2) as bridges to form a 1D chain via hydrogen-bonding contacts. [[Cd(3)(deatrz)(2)Cl(6)(H(2)O)(2)].2H(2)O](n) (2), [[Cd(dmtrz)Cl(2)].1.5H(2)O](n)(3) (dmtrz = 3,5-dimethyl-1,2,4-triazole), and [[Cd(3)(deatrz)(4)Cl(2)(SCN)(4)].2H(2)O](n)(4) are polymeric 1D chains. 2 and 4 were constructed via trinuclear cadmium units bridged by triazole ligands and chloride atoms, while 3 consists of micro(2)-Cl, micro(3)-Cl, and triazole bridges, cross-linked by hydrogen bonding to give a 3D framework. [[Cd(3)(dmatrz)(4)(SCN)(6)]](n)(5) (dmatrz = 3,5-dimethyl-4-amino-1,2,4-triazole) shows a two-dimensional structure whose fundamental units are trinuclear metal cations bridged via triazole ligands. The complex [[Cd(dmtrz)(SCN)(2)]](n)(6) is the first three-dimensional example in N1,N2-didentate-bridged triazole-metal compounds. Six complexes exhibit six types of bridging modes of N1,N2-triazole in combination with single-atom bridges. 2, 4, and 5 are the unprecedented examples of polymeric chains and planes constructed via trinuclear metal ion clusters, whereas 3 is the first example of the micro(3)-Cl bridging mode in triazole-metal complexes. We have briefly discussed the variety of dimensionalities based on the tuning of different organic ligands and anions.

Synthesis and Structure of [DB24C8)Na][Cd(SCN)3. Formation of a novel linear Cd...Cd...Cd chain with a mer-CdN3S3 coordination confirmation and new coiled [(DB24C8)Na]+ cation

We report herein a novel coordination solid, [(DB24C8)Na][Cd(SCN)3] (6) (DB24C8 denotes dibenzo-24-crown-8), which exhibits a new type of [Cd(SCN)3-]infinity chain with two unusual stereochemical characteristics: (1) a mer-CdN3S3 coordination and (2) a linear Cd chain with a Cd...Cd...Cd angle of 180 degrees. In addition, the [(DB24C8)Na]+ monocation adopts a new structural type-a coiled structure-for the combination of crown ether DB24C8 and alkali metal Na+. The title compound crystallizes in a monoclinic unit cell of C2/c space group symmetry with lattice parameters a = 16.110(8) A, b = 20.380(5) A, c = 11.01(1) A, beta = 119.87(3) degrees, and Z = 4. The arrangement of the [Cd(SCN)3-](infinity) chains in the crystal lattice in the title compound is approximately hexagonal, creating triangular channels which are filled with [(DB24C8)Na]+ monocations. It was previously reasoned by us that the coiled [(DB24C8)Na]+ monocation, which lacks inversion or mirror symmetries, should enhance the tendency for the formation of the noncentrosymmetric space group of the title crystal, making it a potential second-order nonlinear optical crystal. Interestingly, however, the title compound crystallizes in a centrosymmetric space group (C2/c) and gives rise to no second harmonic generation (SHG). Previously known [Cd(SCN)3-](infinity) chains adopt fac-CdN3S3 coordination and a zigzag Cd chain configuration with a Cd...Cd...Cd angle of 165 degrees. The zigzag chains can align in either parallel or antiparallel fashion, resulting in efficient or no SHG effects, respectively. The linear Cd.Cd.Cd chain configuration observed in the title compound, on the other hand, makes it indistinguishable between parallel and antiparallel alignments. It is concluded that, to ensure the formation of noncentrosymmetric space groups, it is necessary to employ optically pure chiral cations as spacers and/or controllers. Furthermore, to enhance the nonlinear optical responses, [Cd(SCN)3-]infinity chains with fac-CdN3S3 coordination and parallel alignments of the zigzag Cd chains should be used.