Noncentrosymmetric organic solids with very strong harmonic generation response.

Determination of kryptoracemic compound frequency in the Cambridge Structural Database using CCDC Python API script.

We propose to use the concept of chiral space groups used by crystallography science to define and design lattice robots. Chiral space groups are of great interest because they give all possible sets of discrete displacements having a group structure and a translational symmetry. We explain the analogy between lattice robot kinematics and crystal symmetry, and identify three fundamental properties of lattice robots: (1) discreteness; (2) translational symmetry; and (3) composition. Then we give the possible connector symmetries and orientations into a chiral space group, and the possible sliding and hinge joint locations and orientations compatible with the displacements in the groups. We present a framework for the design of lattice robots by assembling compatible joints and connectors into a chiral space group. Several two-dimensional and three-dimensional examples of designs are given to illustrate the framework. Moreover, we list the symmetries of the two chiral space groups P432 and P622 because they contain the symmetries of all the 65 chiral space groups and allow the design of any lattice system.

Herein, a novel mechano-responsive luminescent (MRL) material based on crystal-to-crystal phase transitions between crystals of a chiral and those of a centrosymmetric space group, accompanied by a change of emission properties, is described. Initially, a gold complex containing a biphenyl moiety, which exhibits an achiral structure in solution, afforded an orange-emitting amorphous phase together with a viscous isotropic oil after evaporation of the solvent. Upon pricking, the orange-emitting oil spontaneously crystallized either in a centrosymmetric or in a chiral space group while simultaneously changing the emission properties. Remarkably, grinding the chiral crystals induced a solid-state phase transition to the achiral crystals under concomitant changes of the emission properties.

Nine compounds based on o-carboxylphenoxyacetate acid (H2OCPA) ligand: [Cu(OCPA)(4,4′-bipy)0.5]n (1), {[Cu2(OCPA)2(4,4′-bipy)2(H2O)]·H2O}n (2), [Co2(OCPA)2(4,4′-bipy)(H2O)4] (3), {[Co(OCPA)(4,4′-bipy)0.5(H2O)]·H2O}n (4), {[Co(OCPA)(4,4′-bipy)1.5]·0.5H2O}n (5), [Ni2(OCPA)2(4,4′-bipy)(H2O)4] (6), {[Ni(OCPA)(4,4′-bipy)1.5]·2H2O}n (7), {[Zn(OCPA)(4,4′-bipy)0.5(H2O)]·H2O}n (8), and [Mn(OCPA)(H2O)]n (9) (4,4′-bipy = 4,4′-bipyridine) were synthesized by hydrothermal methods. The results of structural analyses reveal that the giant structural divergence of the compounds with same metal ions mainly originated from the different amounts of 4,4′-bipy used in syntheses. For Cu-containing compounds, the structural divergences are from one-dimensional (1D) chain 1 to two-dimensional (2D) network 2; for Co, through binuclear 3 to 1D ladder-like 4, and to another different 1D ladder-like chain 5; for Ni, from binuclear 6 to 1D chain 7. But for Zn and Mn, 1D chain 8 and 2D network 9 are obtained with the presence of excess 4,4′-bipy. Compound 9 crystallizes in chiral space group P21 with a second harmonic generation (SHG) efficiency of 0.8 times that of urea. The magnetic studies show that compounds 1 and 9 have antiferromagnetic coupling between the adjacent metallic ions. Compound 4 is a weak ferromagnet based on antiferromagnetic interaction and spin canting. Both the bifurcation temperature of the field-cooled (FC) and zero-field-cooled (ZFC) and the peaks of the real χM′ and the imaginary χM″ parts of alternating current (AC) magnetic susceptibilities are observed at 2.2 K, indicated that the critical temperature Tc is 2.2 K. A very little hysteresis loop is observed with a small coercive field of 20 Oe.

The dimeric complex acetato(η4‐cycloocta‐1,5‐diene)rhodium(I), [Rh(O2CMe)(η4‐cod)]2 (cod = cycloocta‐1,5‐diene), reacts with amino acids [HAA = L‐alanine, (S)‐2‐amino‐2‐phenylacetic acid (L‐phenylglycine), N‐methylglycine, and N‐phenylglycine] and with the amino alcohol (S)‐2‐amino‐2‐phenylethanol to afford the aminocarboxylato(η4‐cycloocta‐1,5‐diene)rhodium(I) complexes [Rh(AA)(η4‐cod)] (AA = deprotonated amino acid = aminocarboxylato ligand) and [(S)‐2‐amino‐2‐phenylethanol](η4‐cycloocta‐1,5‐diene)rhodium(I) acetate, [Rh{(S)‐HOCH2–CH(Ph)‐NH2}(η4‐cod)](O2CMe) (V). The complexes are characterized by IR, UV/Vis, 1H/13C NMR and mass spectroscopy. The achiral N‐phenylglycine ligand gives a chiral N‐phenylglycinato complex [Rh(O2C–CH2–NHPh)(η4‐cod)] (IV) with the amine nitrogen atom becoming the stereogenic center upon metal coordination. Complex IV crystallizes in the tetragonal, chiral space group P43 and the crystal structure reveals twofold spontaneous resolution of a racemic mixture into homochiral helix‐enantiomers. The investigated crystal contained only one type of helix, namely (left‐handed or M‐) 43‐helical chains. This is traced first to an intermolecular N–H···O hydrogen bonding from the stereogenic amino group to a neighboring unligated carboxyl oxygen atom that connects only molecules of the same (R)‐configuration into (left‐handed or M‐) 43‐helical chains. This intrachain homochirality is supplemented, secondly, by the interlocking of adjacent chains with their corrugated van der Waals surface to allow for an interchain transmission of the sense of helicity, building the single crystal from the same homochiral helix‐enantiomer. The enantiomeric amino alcohol complex V crystallizes in the monoclinic, noncentrosymmetric (Sohncke) space group P21. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

1,2-Naphthoquinone-2-semicarbazone (i.e., naftazone) has been characterized by structural analysis (single-crystal X-ray diffraction, powder X-ray diffraction) and by thermal analysis (differential scanning calorimetry, DSC). Although this molecule has no chiral center, the two forms crystallize in chiral space groups: the stable form I (P212121, Z = 4, a = 5.1187(7) Å, b = 5.6092(7) Å, c = 34.847(5) Å; V = 1000.5(2) Å3) and the metastable form II (P21, Z = 2, a = 6.3349(1) Å, b = 3.9263(1) Å, c = 19.790(5) Å, β = 92.424(4)°; V = 491.8(2) Å3). At high concentration (c = 30 g·L−1), the pure stable form I crystallizes regardless of the antisolvent (water) addition rate. At low concentration (c = 15 g·L−1), the pure metastable form II crystallizes at low water addition rate (ψ = 100 mL·h−1); however, the structurally pure form I is also obtained with a high water addition rate (ψ = 72 × 103 mL·h−1). Concomitant polymorphs crystallize at intermediate antisolvent addition rate and concentration. Therefore in the majority of the operative conditions, these results appear to be in contradiction with Ostwald's rule of stages.

The exploration of nonlinear-/linear-optical crystal materials with high performance is an extremely difficult research project. Herein, the two new lead tellurite crystals BaPbTe2O6 and PbVTeO5F were successfully obtained through a facile hydrothermal synthesis strategy. BaPbTe2O6 lies in the noncentrosymmetric (NCS) and chiral orthorhombic space group P212121, featuring a unique ∞1[PbTe2O6] chain consisting of the PbO4 and TeO3 building units, while PbVTeO5F belonging to the centrosymmetric (CS) orthorhombic space group Pbca manifests a 2D layer made up of ∞1[PbO4F2] chains and novel [V2Te2O10F2] clusters. Further, a systematic analysis of lead tellurites finds that the coordination geometries of the Pb atom exert a considerable influence on the connection modes of Pb-O and Te-O building units. BaPbTe2O6 shows a great second-harmonic-generation (SHG) effect of ∼5× the benchmark KH2PO4 (KDP) and a large optical birefringence of 0.086 at 590 ± 3 nm. PbVTeO5F demonstrates a remarkably larger birefringence of 0.142 at 590 ± 3 nm, benefiting from the introduction of the VO5F octahedral unit. Theoretical studies reveal that the large SHG and birefringence in BaPbTe2O6 can be attributed to TeO3 and PbO4 polyhedra with active lone pairs, while the remarkably enlarged birefringence in PbVTeO5F is attributable to the highly distorted octahedral VO5F. The functional orientations of active building units may offer a practical insight into the design of the desired optical functional materials.

Syntheses, structures and properties of three cluster-based coordination polymers: influence of the metal ions on the ligand coordination mode and crystal chirality

We report the use of second harmonic generation (SHG) and temperature resolved second harmonic generation (TR-SHG) for in situ probing and monitoring the structural purification of m-hydroxybenzoic acid (MHBA). Pure and mixtures of the two polymorphic forms of MHBA (metastable Pna21 and stable P21/c) and commercial MHBA were analysed by: DSC, XRPD and SHG. Results obtained with these three techniques are compared and demonstrate for that particular component, the high sensitivity and accuracy of SHG in assessing the polymorphic purity of MHBA. The SHG detection threshold for the metastable polymorph is circa 2 ppm and is several orders of magnitude better than the sensitivity of XRPD (1 wt%) and DSC (only 17 wt%). The proportion of the metastable phase in the commercial MHBA was evaluated to 1 wt% by SHG. Results of TR-SHG measurements performed on commercial MHBA at 5 K min−1 heating rate show that TR-SHG is a good technique for an in situ monitoring of the structural purity. The present study clearly demonstrates that SHG and TR-SHG are relevant and accurate techniques for probing the structural purity and for the monitoring of solid–solid phase transitions provided one of the two varieties crystallizes in a non-centrosymmetric space group.

Organic-inorganic hybrid chiral small-molecule materials combine the inherent properties of both components; however, studies integrating chirality with rare-earth double-perovskite materials are limited. In this work, we synthesized two enantiomers of three-dimensional (3D) hybrid rare-earth double-perovskites, [R-3-HDMP]2CsEu(NO3)6 (1) and [S-3-HDMP]2CsEu(NO3)6 (2), by reacting R-3-HDMP and S-3-HDMP (where 3-HDMP = 3-hydroxy-N,N-dimethylpyrrole) with CsNO3 and Eu(NO3)3 in a 2:1:1 ratio within an acidic solution. Both R-3-HDMPI and S-3-HDMPI crystallize in the chiral space group P212121 at room temperature, exhibiting a transition from SHG-on to SHG-off (SHG = second harmonic generation) upon heating and cooling. The temperature-dependent X-ray single-crystal diffraction analysis carried out on compound 1 and compound 2, before and after the phase transition, disclosed the transformation of their space groups from noncentrosymmetric to centrosymmetric. Additionally, the incorporation of rare-earth elements as hybrid B-site cations imparts exceptional fluorescence properties to the compounds. These materials effectively merge the unique characteristics of chiral molecules with the exceptional luminescence of double-perovskite structures, paving the way for innovative optical devices and advanced information processing technologies.

Four new inorganic-organic hybrid manganese frameworks, formulated as [Mn(Am-Hip)2]·3H2O (1), [Mn2(ip)2(H2O)]·CH3OH (2), [Mn2(OH-ip)2(DMF)]·DMF (3), and (Me2NH2)[Mn4(sdba)4(Hsdba)(H2O)]·3H2O·2DMF (4) (Am-H2ip = 5-aminoisophthalic acid, H2ip = isophthalic acid, OH-H2ip = 5-hydroxyisophthalic acid, and H2sdba = 4,4'-sulfonyldibenzoic acid), have been prepared by solvothermal reactions of Mn(II) ions with different polycarboxylate acids in the presence of LiNO3 or NH4NO3. Single-crystal X-ray diffraction studies reveal that the frameworks of 1-4 contain diverse Mn(II)-oxygen inorganic magnetic chain's sequences, -J1J1J1J1- for 1, -J1J2J1J2- for 2, -J1J1J2J2- for 3, and -J1J2J3J3- for 4. The sequence in 4 has never been seen for the magnetic chain compounds and is a new type of magnetic alternating sequence. Magnetic investigations indicate that these compounds all show weak antiferromagnetic couplings between the adjacent Mn(II) ions. Magnetostructural analyses based on the data of 1-4 and other related Mn(II) chain compounds imply that the magnitude of the magnetic coupling has some relationship with the Mn-O-Mn angle of the μ2-O bridge and the average Mn-O-C-O torsion angle of the carboxylate bridges. Compounds 2 and 4 crystallize in chiral and acentric space groups, and they both exhibit powder second harmonic generation (SHG) efficiencies approximately 0.6 and 0.9 times, respectively, that of the standard potassium dihydrogen phosphate (KDP) powder. In addition, the dielectric properties of 2 and 4 were also investigated.

Alkene migration to the end-terminal carbon bearing a phenyl group over a chiral siloxy carbon center in Heck reaction

The two acentric aluminoborates (ABOs) [M(dap)3]2{Al[B5O7(OH)3][B5O8(OH)2][B6O9(OH)2]} (M and dap represent Co(1)/Ni(2) and 1,2-diaminopropane, respectively) templated by chiral metal complexes (CMCs) have been solvothermally synthesized. The isostructural 1 and 2 crystallize in the chiral space group P21. Both feature unprecedented 2D wavelike layers built by three kinds of oxoboron (B-O) clusters ([B5O7(OH)3]2-, [B5O8(OH)2]3-, and [B6O9(OH)2]2-) and AlO4 tetrahedra. In the frameworks of 1 and 2, AlO4 and [B6O9(OH)2]2- units are strictly alternating into 1D chains. Further, [B5O8(OH)2]3- clusters link adjacent chains to form 2D wavelike layers. In addition, the [B5O7(OH)3]2- units as the hanging clusters are supported on two sides of the wavelike layers through AlO4 groups, resulting in the first example of a wavelike layer ABO composed of three kinds of B-O clusters and four types of channels. 1 and 2 display second-harmonic generation (SHG) signals about ∼1.3 and ∼0.93 times that of KH2PO4 (KDP) and belong to the class of wide-band-gap semiconductors.

Coordination compound [Os(SC6F4H-4)2(SC6F3H-4(SC6F4H)-2)(C6H5)] is obtained during the thermolysis of [Os(SC6F4H-4)4(PPh3)] in non-dried toluene, as a product of C–F bond cleavage. The complex presents the expected trigonal–bipyramidal coordination geometry, with a thiolate-sulfanyl κ2 S,S’-ligand chelating the metal center in axial and equatorial sites. The complex was crystallized in the centrosymmetric space group C2/c and in the non-centrosymmetric space group Pna21. In both forms, the crystal is a RS racemate, with the chiral center being the axially coordinated sulfanyl S atom. In the case of the non centrosymmetric space group, the asymmetric unit retained for the refinement consists of two independent molecules related by a pyramidal sulfur inversion at the stereogenic center. Cell parameters: form I, C2/c, a = 20.8459(14) A, b = 12.2646(12) A, c = 25.253(3) A, β = 91.582(7)°; form II, Pna21, a = 16.208(2) A, b = 16.500(3) A, c = 23.604(3) A. An Os(IV) coordination complex bearing a thiolate-sulfanyl κ2 S,S’-ligand was crystallized in two spaces groups, C2/c with one molecule in the asymmetric unit, and Pna21 with two enantiomeric molecules in the asymmetric unit.

Supramolecular assembly based on a series of meso-tetrakis( p-methoxyphenyl)porphrin complexes