Synthesis, crystal structures and photoluminescence properties of Sm-based enantiomeric pair

Novel Sm-based enantiomeric pair, generally formulated Sm(DBM)₃L (L_R,R in 1, L_S,S in 2, DBM = dibenzoylmethanate) have been successfully prepared via the reaction of Sm(DBM)₃·2H₂O with chiral ligands L_R,R (−)-4,5-pinene bipyridine and L_S,S (+)-4,5-pinene bipyridine (Scheme 1), respectively. The crystal structure analysis of 1 and 2 reveal that they crystallize in chiral space group P2₁ of monoclinic system. The central Sm(III) ion is octacoordinate with six β-diketonate oxygen atoms and two chiral pinene bipyridine nitrogen atoms, forming a coordination polyhedron best described as the distorted square antiprism (SA). The CD spectra (Fig. S1) further confirm that 1 and 2 are enantiomers. The photoluminescence investigations of 1 and 2 demonstrate that they display deep-red luminescence characteristic of the Sm³⁺_.     

Synthesis and characterization of macrocyclic nickel(II) complexes with α-methylbenzyl groups as chiral pendants

Novel nickel(II) hexaaza macrocyclic complexes, [Ni(L^R,R)](ClO₄)₂ (1) and [Ni(L^S,S)](ClO₄)₂ (2), containing chiral pendant groups have been synthesized by an efficient one-pot template condensation and characterized (L^R,R/S,S = 1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. Each complex has a square-planar coordination environment for the nickel(II) ion, and is either an R or an S enantiomorph depending on the pendant groups. The circular dichroism spectrum of 1 showed a negative, positive and negative peak at 345, 440, and 492 nm, respectively, and that of 2 exhibited an enantiomeric pattern.     

Reactions of benzophenone imine complex [Tp(NH═CPh2)(PPh3)Ru–Cl] with alkyne and dimerization of terminal alkynes in the presence of Et3N

Treatment of benzophenone imine complex [Tp(PPh₃)(NH═CPh₂)Ru–Cl] (1) {Tp═HB(pz)₃, pz = pyrazolyl} with 4-Ethynyltoluene in the presence of H₂O in distilled ethanol afforded the chelate alkenyl ketone complex [Tp(PPh₃)RuCCH₂(p-MeC₆H₄)═CHC(O)(p-MeC₆H₄)] (2). On the other hand, reaction of 1 with HC≡C(O)OR₁ in R₂OH produced the chelate vinyl ether complexes [Tp(PPh₃)Ru–C(OR₂)═CHC(O)OR₁] (3a, R₁ = Me, R₂ = Me; 3b, R₁ = Et, R₂ = Me; 3c, R₁ = Et, R₂ = Et; 3d, R₁ = Me, R₂ = Et), respectively. Preliminary results on the catalytic activity of 1 are also presented. Intriguingly, complex 1 is found to catalyze the dimerization of terminal alkynes HC≡CR (R = p-MeC₆H₄, C(O)OCH₃) in the presence of Et₃N to give eynes. The structures of 3c and 3d have been determined by X-ray diffraction analysis.     

Fluorescence sensors based on chiral polymer for highly enantioselective recognition of phenylglycinol

Chiral polymer P-1 incorporating (R,R)-salen-type unit was synthesized by the polymerization of (R,R)-1,2-diaminocyclohexane with 2,5-dibutoxy-1,4-di(5-tert-butylsalicyclaldehyde)-phenylene (M-1) via nucleophilic addition-elimination reaction, and chiral polymer P-2 incorporating (R,R)-salan-type unit could be obtained by the reduction reaction of P-1 with NaBH₄. The fluorescence response of two chiral polymers P-1 and P-2 on (R)- or (S)-phenylglycinol were investigated by fluorescence spectra. The fluorescence intensities of two chiral polymers P-1 and P-2 show gradual enhancement upon addition of (R)- or (S)-phenylglycinol and keeps nearly linear correlation with the concentration molar ratios of (R)- or (S)-phenylglycinol. But both P-1 and P-2 exhibited more sensitive response signals for (S)-phenylglycinol. The values of enantiomeric fluorescence difference ratio (ef) are 1.84 and 2.05 for P-1 and P-2, respectively. The results also showed that two chiral polymers P-1 and P-2 can also be used as fluorescence sensors for enantiomer composition determination of phenylglycinol.     

Zirconium phosphonate immobilized chiral amino alcohol for heterogeneous enantioselective addition of diethylzinc to benzaldehyde

The chiral (1R,2S)-(−)-2-amino-1,2-diphenylethanol and (1S,2R)-(+)-2-amino-1,2-diphenylethanol had been immobilized on the layered frame of zirconium phosphate to obtain zirconium phosphonates (1R,2S)-(−)-4a and (1S,2R)-(+)-4b. The enantioselective addition of Et₂Zn to benzaldehyde using zirconium phosphonates (1R,2S)-(−)-4a and (1S,2R)-(+)-4b as heterogeneous catalysts yielded secondary alcohol in 80.1% yield and e.e. values of up to 54.3%, which was only 7.6% e.e. lower than that using the corresponding ligands (1R,2S)-(−)-2a and (1S,2R)-(+)-2b as homogeneous catalysts. The zirconium phosphonates (1R,2S)-(−)-4a and (1S,2R)-(+)-4b were characterized by IR, SEM, XRD and TG analysis. SEM and XRD data showed that the catalysts (1S,2R)-(+)-4b and (1R,2S)-(−)-4a were in aggregate and mesopore structure with the same interlayer spacing 2.48 nm and pore diameter 5.6 nm.     

Experimental and theoretical study of the ferroelectric and piezoelectric behavior of strontium-doped PZT

Theoretical data using ab initio perturbed ion calculation were compared with ferroelectric and piezoelectric experimental data of strontium doped PZT. Various concentrations of SrO in PZT at constant temperature and sintering time were carried out. Experimental results, such as the remanent polarization, P_R of 6.9–8.9 μC/Cm², the coercive field, E_C of 6.6–7.8 kVcm, and the planar coupling factor, Kp of 0.45–0.53, were compared with the energy of Zr⁴⁺ and Ti⁴⁺ ion dislocation and the lattice interaction energy which show that strontium increment in PZT alter the energies and increase the values of piezoelectric and ferroelectric variables. Calculations of lattice energy of the rhombohedral phase show that a phase non-stability is coincident with increasing experimental values of the P_R, E_C and Kp.     

Azocoupling products. V. Electronic spectroscopy study of two azocoupling products of 1-(4-hydroxy-6-methyl-pyrimidin-2-yl)-3-methyl-pyrazolin-5-one

A systematic study of the effect of solvent, sample concentration, time and acid or alkali addition, respectively of pH′, upon the electronic absorption spectra of two dyes 7 and 8, as well as the pK_a′ determination of these dyes was carried out. In C₆H₆, CHCl₃, DMSO, and acidic media (AcOH, acidified EtOH) these dyes that theoretically may be involved in azo–hydrazone tautomerism have been detected only as hydrazone tautomers 7c and 8c. In exchange, in neutral and alkalized EtOH, respectively in DMF, in concentration range 10⁻⁴–10⁻⁶ mol L⁻¹ these tautomers are in equilibrium with monodeprotonated (9, 10) and twice deprotonated (13, 14) species. By increase of pH, or by dilution, the equilibrium shifts increasingly towards the deprotonated species. The monodeprotonated species, correspond also to a hydrazone structure 9, 10, whilst the doubly deprotonated species represent a common dianion that should be predominantly azo in character (13, 14).     

Zirconium phosphonate immobilized chiral amino alcohol for heterogeneous enantioselective addition of diethylzinc to benzaldehyde

The chiral (1R,2S)-(−)-2-amino-1,2-diphenylethanol and (1S,2R)-(+)-2-amino-1,2-diphenylethanol had been immobilized on the layered frame of zirconium phosphate to obtain zirconium phosphonates (1R,2S)-(−)-4a and (1S,2R)-(+)-4b. The enantioselective addition of Et₂Zn to benzaldehyde using zirconium phosphonates (1R,2S)-(−)-4a and (1S,2R)-(+)-4b as heterogeneous catalysts yielded secondary alcohol in 80.1% yield and e.e. values of up to 54.3%, which was only 7.6% e.e. lower than that using the corresponding ligands (1R,2S)-(−)-2a and (1S,2R)-(+)-2b as homogeneous catalysts. The zirconium phosphonates (1R,2S)-(−)-4a and (1S,2R)-(+)-4b were characterized by IR, SEM, XRD and TG analysis. SEM and XRD data showed that the catalysts (1S,2R)-(+)-4b and (1R,2S)-(−)-4a were in aggregate and mesopore structure with the same interlayer spacing 2.48 nm and pore diameter 5.6 nm.     

Supported organometallic complexes. Part 37: synthesis and structures of diamine-bis(methoxyethyldimethylphosphine)ruthenium(II) complexes

The first two examples of diamineruthenium(II) complexes containing the hemilabile methoxyethyldimethylphosphine ligand, Cl₂Ru(en)(η¹-Me₂PCH₂CH₂OMe)₂ (2a) and Cl₂Ru[(R,R)-dpen](η¹-Me₂PCH₂CH₂OMe)₂ (2b) (en=1,2-diaminoethane, (R,R)-dpen=1R,2R-1,2-diamino-1,2-diphenylethane) have been synthesized and structurally characterized.     

Synthesis and properties of helical polyacetylenes containing carbazole

Novel acetylene monomers containing carbazole with chiral menthyl and bornyl groups, 9-(1R,2S,5R)-menthyloxycarbonyl-2-ethynylcarbazole (1), 9-(1S,2R,5S)-menthyloxycarbonyl-2-ethynylcarbazole (2), 9-(1R,2S,5R)-menthyloxycarbonyl-3-ethynylcarbazole (3) and 9-(1S)-bornyloxycarbonyl-2-ethynylcarbazole (4) were synthesized and polymerized with a Rh catalyst to give the corresponding polymers [poly(1)-poly(4)] with moderate M_n value of (11.5-92.2) × 10³ in good yields (77-89%). CD spectroscopic studies revealed that poly(1), poly(2) and poly(4) took predominantly one-handed helical structure in CHCl₃, THF, toluene, and CH₂Cl₂, while poly(3) did not. Addition of methanol to CHCl₃ solutions of poly(1) and poly(2) resulted in the formation of aggregates showing smaller CD signals at 275 and 320 nm. The helical structure of poly(1) and poly(2) was very stable against heating. The polymers emitted fluorescence in 0.40-2.90% quantum yields. Poly(4) exhibited an obvious oxidation peak at 1.10 V. The polymers were thermally stable below 300 °C.     

Coordination modes in zirconium β-diketiminate complexes

Reaction of β-diketiminate lithium salts, nacnac^RLi(THF) (R = 2,6-xylyl (1a), R-CH(Me)Ph (1b)), with ZrCl₄ or ZrCl₄·THF yielded the mono-diketiminate complexes nacnac^RZrCl₃(THF), 2a and 2b. Complex 2a did not react further with a second equivalent of 1a, but with CpLi or IndLi to form pseudo-tetrahedral complexes 3 and 4. No product could be isolated from reaction of 2b with CpLi. Coordination of the diketiminate ligand in 2a is best described as a distorted κ²-, in-plane coordination. Complexes 3 and 4, however, display a haptotropic shift of the diketiminate ligand and its coordination is best described as κ²,η²-coordination. Although not previously described, analyses of available structures in the literature reveal that non-symmetric κ²,η²-coordination is an independent coordination mode, which exists next to the previously described “η⁵-like” coordination.     

Synthesis, structure and ethylene (co)polymerization behavior of new nonbridged half-metallocene-type titanium complexes based on bidentate β-enaminoketonato ligands

A series of novel half-metallocene-type titanium complexes CpTiCl₂[PhNC(R₂)CHC(R₁)O] (2a, R₁ = Cy, R₂ = CF₃; 2b, R₁ = ^tBu, R₂ = CF₃; 2c, R₁ = Ph, R₂ = CF₃; 2d, R₁ = Ph, R₂ = CH₃) have been synthesized by treating CpTiCl₃ with the corresponding bidentate β-enaminoketonato ligands PhNC(R₂)CHC(R₁)OH in the presence of triethylamine. Single crystal X-ray diffraction revealed that complex 2b adopts distorted square-pyramid geometry around the titanium center. The complexes 2a-d were investigated as the catalysts for ethylene polymerization and the copolymerization of ethylene with norbornene. All the complexes were active towards ethylene (co)polymerization in the presence of modified methylaluminoxane, and produced high molecular weight (co)polymers. The catalytic activity and the norbornene incorporation were highly dependent upon catalyst and reaction conditions employed. Among four complexes, 2c exhibited both high catalytic activity and efficient norbornene incorporation under the same conditions, affording high molecular weight copolymers with unimodal molecular weight distributions.     

Linked macrocyclic systems. Interaction of copper(I) with tris-ring N2S2-donor macrocycles and their single-ring analogues

The interaction of two tri-linked N₂S₂-donor macrocyclic ligands, 1 (R = H) and 2 (R = H), and their related single ring derivatives, 3 (R = H) and 4 (R = CH₂C₆H₅), with copper(I) is reported. Solid 3:1 (metal:ligand) complexes of type [Cu₃L](PF₆)₃ (L = 1 and 2, R = H) and single ring derivatives of type [CuL]PF₆ (L = 3, R = H; L = 4, R = CH₂C₆H₅) were isolated; the X-ray structure of [CuL]PF₆ (L = 3, R = H) showed that the four macrocyclic donor atoms coordinate to the copper(I) in a quasi-tetrahedral manner (Cu–N 2.089, 2.096(4); Cu–S 2.239, 2.264(2) Å, X–Cu–Y 104.5(1)–115.4(1))°.     

(R,R)-salen/salan-based polymer fluorescence sensors for Zn detection

(R,R)-salen-based polymer fluorescence sensor P-1 could be synthesized by the polymerization of 5,5′-(isoquinoline-5,8-diylbis(ethyne-2,1-diyl))-bis(3-tert-butyl-2-hydroxybenzaldehyde) (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via nucleophilic addition-elimination reaction, and (R,R)-salan-based polymer sensor P-2 could be obtained by the reduction reaction of P-1 with NaBH₄. The fluorescence response behaviors of two chiral polymers P-1 and P-2 on Zn²⁺ were investigated by fluorescence spectra. The fluorescence intensities of P-1 and P-2 can exhibit gradual enhancement upon addition of Zn²⁺. Compared with other cations, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Cd²⁺, Cr³⁺ and Pb²⁺, Zn²⁺ can lead to the pronounced fluorescence enhancement as high as 22.8-fold for P-1 and 3.75-fold for P-2, respectively. The results show that P-1 and P-2 incorporating (R,R)-salen/salan moieties as receptors in the polymer main chain backbone can exhibit high sensitivity and selectivity for Zn²⁺ detection.     

Eu5(μ4-OH)(μ3-OH)4(μ-DBM)4(DBM)6 (DBM=dibenzoylmethide): a novel Eu5 square-pyramid polynuclear complex with a rare μ4-OH bridging mode

The reaction of EuOCl (EuCl₃) with dibenzoylmethane (HDBM) in the presence of N-methylmorpholine yields a novel Eu₅ square-pyramid polynuclear complex with a rare μ₄-OH bridging mode, Eu₅(μ₄-OH)(μ₃-OH)₄(μ-DBM)₄(DBM)₆ (1). The compound was characterized by elemental analysis, IR, fluorescence and Mössbauer spectra as well as by an X-ray single crystal structure determination. Crystallographic data for 1, C₁₅₀H₁₁₅Eu₅O₂₅, monoclinic, P2₁/c, a=22.223(5), b=17.427(1), c=35.708(5) Å, β=100.11(2)°, V=13614(4) ų, Z=4, R₁=0.0979, wR₂=0.1695.     

Homo- and R/S-copolymerizations of chiral methylpropargyl esters carrying pyrene moieties, and optical properties of the formed polymers

Pyrene-functionalized chiral methylpropargyl esters, (R)-3-butyn-2-yl-1-pyrenebutyrate [(R)-1], (S)-3-butyn-2-yl-1-pyrenebutyrate [(S)-1], (R)-3-butyn-2-yl-1-pyrenecarboxylate [(R)-2], and 3-butyn-2-yl-1-pyrenecarboxylate [(R,S)-2] were polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] to obtain the corresponding polymers with moderate molecular weights (M_n: 10?500-66?500) in good yields (82-97%). All the polymers were soluble in CHCl₃, CH₂Cl₂, and THF. The polarimetric and CD spectroscopic data indicated that poly[(R)-1], poly[(S)-1], and poly[(R)-2] existed in a helical structure with predominantly one-handed screw sense in these solvents. The helical structure of poly[(R)-1] and poly[(S)-1] was stable upon heating and addition of MeOH, while that of poly[(R)-2] changed upon MeOH addition. The copolymerization of (R)-1 with (S)-1 was also conducted to obtain the copolymers satisfactorily. Poly[(R)-1], poly[(S)-1], and poly[(R)-2] emitted fluorescence smaller than the corresponding racemic copolymers. The fluorescence intensity was tuned by the addition of MeOH to THF solutions of the polymers.     

New bis-o-iminosemiquinonate aluminium(III) complexes

The first aluminium(III) complexes based on sterically hindered 4,6-di-tert-butyl-N-(2,6-di-iso-propyl-phenyl)-o-iminobenzoquinone (imQ) of general formula imSQ₂AlR (where imSQ — is a radical anion of imQ, R = I (1), NCS (2) and N₃ (3)) were synthesized. Compounds 1–3 demonstrate biradical X-band EPR spectra in frozen toluene matrix. The crystalline samples of 1–3 were characterized using magnetic susceptibility measurements. The antiferromagnetic coupling between spins of o-iminosemiquinonate radicals in 1–3 is predominant and, as the result, the singlet ground state for pentacoordinated biradical compounds is observed. The molecular structures of all the complexes obtained have been established by the single crystal X-ray analysis.     

Facile C–N cleavage reactions of secondary and tertiary alkyl amines by P,O chelating rhodium and iridium complexes

The reactions of Cp*MCl(MDMPP-P,O) (1: M=Rh; 3: M=Ir; MDMPP-P,O=PPh₂(C₆H₃-2-O-6-MeO)) with secondary or tertiary alkyl amine (R₂NH or R₃N) in the presence of KPF₆ underwent a C–N cleavage of amine to afford primary amine complex [Cp*M(MDMPP-P,O) (RNH₂)](PF₆) (2: M=Rh; 4: M=Ir).     

Networking chiral coordination polymers through amide hydrogen bond interactions: Thermal stability and optical SHG investigations

Complementary amide H-bond interactions of chiral C₂-symmetric bis(amide) ligand BINDC, (N,N′-bis(isonicotinoyl)-(1R,2R)-diaminocyclohexane) in Zn(BINDC)Cl₂ (1), Zn(BINDC)Br₂ (2) and Ag(BINDC)NO₃ (3) metal-organic frameworks (MOFs) lead to the formation of hierarchical network structures. The strong H-bond interactions coupled with coordinate bond leads to enhanced thermal stability to the materials. Moreover, the MOFs show solid state second harmonic generation (SHG) and good optical transparency in the visible range.     

Ethylene/hexene living copolymerization and ethylene/methyl 10-undecenoate copolymerization by titanium complexes bearing phenoxy-phosphine or thiophenoxy-phosphine ligands

Several non-metallocene-type titanium(IV) complexes containing phenoxy-phosphine or thiophenoxy-phosphine ligands of type, (2-R₁-4-R₂-6-PPh₂-C₆H₂X)₂TiCl₂ (2a: X = O, R₁ = R₂ = t-Bu; 2b: X = O, R₁ = R₂ = cumyl; 2c: X = S, R₁ = SiMe₃, R₂ = H) have been synthesized by treating TiCl₄ with the corresponding ligands 2-R₁-4-R₂-6-PPh₂-C₆H₂XH in the presence of n-BuLi. The complexes 2a-c were investigated as the catalysts for ethylene with 1-hexene and/or polar alkenes copolymerizations. The catalytic activity and the comonomer incorporation were highly dependent upon catalyst and reaction conditions employed. Among these complexes, 2a can not only promote ethylene/1-hexene living copolymerization at room temperature, but also can utilize ethylene with methyl 10-undecenoate copolymerization.