The Impact of Education on Fertility During the Chinese Reform Era (1980-2018): Changes Across Birth Cohorts and Interaction with Fertility Policies.

We examined the influence of education on fertility decisions in contemporary China, drawing upon theoretical insights that emphasise the role of social institutions, gender relations, and life course dynamics in shaping family behaviour. This led us to propose a set of hypotheses that explain the differential effect of education on each parity. We used information on female cohorts born between 1960 and 1989, coming from the China Family Panel Studies for 2010-2018. We applied event history models with both independent and simultaneous equations models to account for selection and endogeneity effects. The results point to a substantial contribution of the increased educational attainment in the population in the fertility decline and current low levels of fertility, beyond the role of fertility policies. Consistent with our hypotheses, the results show that woman's educational attainment has a strong negative effect on the hazard of bearing a second or third child. Male partner's educational attainment also has a negative effect on the hazard of transition to a second or third birth, yet with a weaker intensity. We also found that the negative effect of education on second birth rates significantly declines across birth cohorts. The results show little educational differentials in the probability of bearing a first child, while the better educated postpone first births. Moreover, the effect of fertility policies, measured at the individual level, gradually increases with the level of education.

Mechanistic Study of B(C6F5)3-Catalyzed Transfer Hydrogenation of Aldehydes/Ketones with PhSiH3 and Stoichiometric Water.

A DFT study was performed on the mechanisms of B(C6F5)3-catalyzed transfer hydrogenation of aldehydes/ketones, using PhSiH3 and stoichiometric water. Path B2 includes a stepwise Piers SN2-Si process, H- transfer, and hydrolysis desilylation of siloxane, in which the hydrolysis desilylation step is rate-determining. Path C1 is first determined, involving a B(C6F5)3-catalyzed concerted addition step of 2H2O to carbonyl generating R1R2C(OH)2, a subsequent SN2-Si dehydroxylation step of R1R2C(OH)2 giving R1R2C=OH+ and (C6F5)3B-H-, and final H- transfer producing the respective alcohol R1R2CHOH. A B(C6F5)3-catalyzed H2 generation process (Path H0) is determined. Path B2 is the only mechanism for the stepwise method. Using a one-time one-pot feeding method, alkyl/aryl aldehydes, dialkyl ketones, and alkyl aryl ketones (1a-g) can be reduced into alcohols chemoselectively and effectively at room temperature. More than 1 equiv of water over substrates is necessary. Herein, Path C1 is the dominant transfer hydrogenation pathway, and the H2 generation is efficiently inhibited, by the competitive advantage of Path C1 and initial dominant existence of the complexes IM0 and IM1-x. The diaryl ketones (1h,1i) cannot be efficiently reduced into the respective alcohols using the one-time feeding one-pot method. The barriers of C-TS1-h/i are obviously higher than those of C-TS1-a-g, attributed to the electron-donating and space effects of the two aryls on carbonyl C. The possible Paths B2 and C1 of transfer hydrogenation have no competitive advantage with Path H0. The DFT results are consistent with the experiments.

From VIB- to VB-Group Transition Metal Disulfides: Structure Engineering Modulation for Superior Electromagnetic Wave Absorption.

The laminated transition metal disulfides (TMDs), which are well known as typical two-dimensional (2D) semiconductive materials, possess a unique layered structure, leading to their wide-spread applications in various fields, such as catalysis, energy storage, sensing, etc. In recent years, a lot of research work on TMDs based functional materials in the fields of electromagnetic wave absorption (EMA) has been carried out. Therefore, it is of great significance to elaborate the influence of TMDs on EMA in time to speed up the application. In this review, recent advances in the development of electromagnetic wave (EMW) absorbers based on TMDs, ranging from the VIB group to the VB group are summarized. Their compositions, microstructures, electronic properties, and synthesis methods are presented in detail. Particularly, the modulation of structure engineering from the aspects of heterostructures, defects, morphologies and phases are systematically summarized, focusing on optimizing impedance matching and increasing dielectric and magnetic losses in the EMA materials with tunable EMW absorption performance. Milestones as well as the challenges are also identified to guide the design of new TMDs based dielectric EMA materials with high performance.

Mechanistic insight into B(C6F5)3 catalyzed imine reduction with PhSiH3 under stoichiometric water conditions.

A DFT and experimental study on the mechanism of B(C6F5)3 catalyzed imine reduction is performed using PhSiH3 as reductant under stoichiometric water conditions. Ingleson's path B is reconfirmed here. And four novel (C6F5)3B-OH2 induced pathways (paths C2, C3, D2 and D3) entirely different from all the previous mechanisms were determined for the first time. They are all B(C6F5)3 and water/amine catalyzed cycles, in which the nucleophilic water or amine catalyzed addition step between PhSiH3 and the N-silicon amine cation is the rate-determining step of paths C2/D2 and C3/D3 with activation Gibbs free energy barriers of 23.9 and 18.3 kcal mol-1 in chloroform, respectively, while the final desilylation of the N-silicon amine cation depends on an important intermediate, (C6F5)3B-OH-. The competitive behavior of the 5 paths can explain the experimental facts perfectly; if all the reactants and catalysts are added into the system simultaneously, water amount and nucleophiles (excess water and produced/added amine) provide on-off selectivity of the pathways and products. 1 eq. water leads to quick formation of (C6F5)3B-OH-, leading to B-II being turned off, and nucleophiles like excess water and produced/added amine switch on CD-II, leading to production of the amine. B-I' of Ingleson's path B is the only mechanism for anhydrous systems, giving N-silicon amine production only; B-I and C-I are competitive paths for systems with no more than 1 eq. water, producing the N-silicon amine and the [PhHC[double bond, length as m-dash]NHPh]+[(C6F5)3B-OH]- ion pair; and paths C2, C3, D2 and D3 are competitive for systems with 1 eq. water and nucleophiles like excess water or added/produced amine, directly giving amination products.

Trichlorido(1,3-dimethyl-2,3-di-hydro-1H-imidazol-2-yl-idene-κC (2))aluminium(III).

The title compound, [Al(C5H8N2)Cl3], was prepared by a thermolytic decomposition under high-vacuum conditions and presents a formal adduct of an Arduengo carbene, 1,3-dimethyl-1H-imidazol-2-yl-idene, and aluminium trichloride. The Al atom adopts a pseudo-tetra-hedral CCl3 coordination environment. All N and C atoms, the Al atom, one of the Cl atoms, and all aromatic H atoms of the mol-ecule lie on a mirror plane. As a result of the mirror symmetry of the mol-ecule, the H atoms of all methyl groups are disordered between symmetry-equivalent positions.

Bis(1,3-dimethyl-1H-imidazolium) hexa-fluoro-silicate methanol 0.33-solvate.

The title compound, 6C5H9N2 (+)·3SiF6 (2-)·CH3OH, (I), was prepared by recrystallization of the crude salt from methanol along with solvent-free 2C5H9N2 (+)·SiF6 (2-) (II). Crystals of these solvatomorphs can be separated manually. The solvate (I) crystallizes in a rare hexa-gonal space group P6/mcc. Its asymmetric unit comprises one half of an imidazolium cation bis-ected by the crystallographic m-plane, one-sixth and one-twelfth of two crystallographically independent SiF6 (2-) dianions (Si atoms are located on the 3.2 and 6/m inversion centres), and one-twelfth of a methanol mol-ecule (C atoms are situated on the 622 inversion centres, other atoms are disordered between general positions). In (I), all F atoms of 3.2-located SiF6 (2-) dianions participate in the formation of symmetry-equivalent contacts to the H atoms of imidazolium fragments, thus forming rod-type ensembles positioned on the -6 axes. These 'pillar' rods are, in turn, F⋯H inter-linked through SiF6 (2-) dianions disordered around the 6/m centres. The twelvefold disordered methanol mol-ecules are appended to this array by O-H⋯F hydrogen bonds to the 6/m located SiF6 (2-) dianions. In terms of graph-set notation, the first and second level networks in (I) are N 1 = C 2 (2)(7)[3R 4 (4)(14)]D 2 (2)(4) and N 2 = D 2 (2)(5) (C-H⋯O hydrogen bonds are not considered). After locating all symmetrically independent atoms in the cation and anions, there remained a strong (> 3 e Å(-3)) residual electron density peak located at the 622 inversion centre. Treatment of this pre-refined model with the SQUEEZE procedure in PLATON [Spek (2009). Acta Cryst. D65, 148-155] revealed two voids per unit cell, indicative of the presence of the solvent methanol mol-ecule disordered about the 622 inversion centre.

Bis(1,3-dimethyl-1H-imidazolium) hexa-fluoro-silicate: the second monoclinic polymorph.

The title compound, 2C5H9N2 (+)·SiF6 (2-), (I), crystallized as a new polymorph, different from the previously reported one (Ia) [Light et al. (2007 ▶) private communication (refcode: NIQFAV). CCDC, Cambridge, England]. The symmetry [space groups P21/n for (I) and C2/c for(Ia)] and crystal packing patterns are markedly different for this pair of polymorphs. In (I), all imidazolium cations in the lattice are nearly parallel to each other, whereas a herringbone arrangement can be found in (Ia). In (I), each SiF6 (2-) dianion forms four short C-H⋯F contacts with adjacent C5H9N2 (+) cations, resulting in the formation of layers parallel to the ac plane. In (Ia), the C-H⋯F contacts are generally longer and result in the formation of layers along the bc plane.

Trichlorido(tetra-hydro-furan){(1,2,3,3a,7a-η)-1-[2-(1-trimethyl-silyl-1H-imidazol-2-yl-κN)-1-methyl-prop-yl]inden-yl}zirconium(IV).

The title compound, [ZrCl(3)(C(19)H(25)N(2)Si)(C(4)H(8)O)], was prepared from bis-(N,N-dimethyl-amido-κN)(2-{2-[(1,2,3,3a,7a-η)-inden-yl]-2-methyl-prop-yl}-1H-imidazolido-κN(1))zirconium(IV) [(C(16)H(16)N(2))Zr(NMe(2))] by reaction with excess Me(3)SiCl in tetra-hydro-furan (THF) at elevated temperature. The crystal studied contained a minor non-merohedral twin contaminant [6.3 (4)%] which was taken into account during the refinement. The coordination polyhedron of the Zr(IV) atom is a distorted octa-hedron [assuming that the five-membered ring of the indenyl group (Cp) occupies one coordination site], with the Cp group and a THF O atom at the apical positions and the three Cl and ligating N atoms at the equatorial positions. The Zr, Si and the methyl-ene C atoms deviate noticeably from the imidazole ring plane [by -0.197 (5), -0.207 (5) and 0.119 (6) Å, respectively]. The THF ligand adopts an envelope conformation.

{2-[(η-Cyclo-penta-dien-yl)diphenyl-meth-yl]-1H-imidazolido-κN}bis-(N,N-diethyl-amido)-titanium(IV).

The chemically achiral title mol-ecule, [Ti(C(4)H(10)N)(2)(C(21)H(16)N(2))], crystallizes in the chiral space group P2(1). All three N atoms coordinating to the Ti(IV) atom adopt planar environments [sums of valence angles = 359.5 (6), 360.0 (7) and 360.0 (6)°], which is indicative of pπ-dπ donation from all of these N atoms to the metal and, thus, of the formal 18 e(-) nature of the complex. The overall coordination about the Ti(IV) atom is distorted tetra-hedral, assuming the cyclo-penta-dienyl ring occupies one coordination site. The Ti-N(imidazole) amide-type bond is longer by approximately 0.16 Šthan the other two Ti-N(amide) bonds.

rac-(OC-6-33)-bis-[2-(N-Benzyl-methyl-imino-meth-yl-κN)-1H-imidazol-1-ido-κN]bis(ethyl-amido)-titanium(IV).

The title compound, [[Ti(C(2)H(10)N)(2)(C(11)H(10)N(3))(2)] or Ti(C(11)H(10)N(3))(2)(NEt(2))(2)], was prepared by direct reaction of 2-(N-phenyl-methyl-imino-meth-yl)-1H-imidazole and [Ti(NEt(2))(4)]. The Ti(IV) atom is in a pseudo-octa-hedral coordination environ-ment with the imidazolido-group N-atoms occupying apical positions and amido- and imino-N-atoms cis-located in the equatorial plane. The presence of two bidentate chelating ligands determines the chirality of the Ti(IV) atom. The crystallographically independent unit, except for its phenyl rings, adopts nearly pseudo-C(2) symmetry (rotation around a twofold axis passing through the Ti atom and the centre of the imino-N⋯imino-N segment). The Ti-N(amido), Ti-N(imidazolido), and Ti-N(imino) bond lengths essentially differ, increasing by approximately 0.2 Šin the series. All ligating N atoms are in a nearly planar environment, which is indicative of additional pπ-dπ donations towards the metal atom. The two diaza-metallacyclic units are planar within 0.03 and 0.05 Å.

2-{(E)-N-[2-(1H-Inden-3-yl)eth-yl]imino-meth-yl}-1H-imidazole.

The asymmetric unit of the title compound, C(15)H(15)N(3), contains two crystallographically independent mol-ecules with very similar geometries. The imidazole and indenyl planes are approximately orthogonal, making dihedral angles of 88.21 (9) and 83.08 (9)%deg; in the two independent molecules. In the crystal, the imidazole units are linked by N-H⋯N hydrogen bonds into chains parallel to the 101) plane stretched in the diagonal direction [translation vector ([Formula: see text],1,0); C(4) motif]. Within a chain, there are two types of symmetrically non-equivalent alternating H-bonds which slightly differ in their parameters.

Detection of carbohydrates using a pre-column derivatization reagent 1-(4-isopropyl) phenyl-3-methyl-5-pyrazolone by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry.

A reagent, 1-(4-isopropyl) phenyl-3-methyl-5-pyrazolone (PPMP) has been synthesized and used for high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) determination of pre-column labeled carbohydrates. Monosaccharides have been quantitatively converted into mono-PPMP-labeled derivatives with 28% aqueous ammonia as a catalyst at 80 degrees C during 70 min. Mono-PPMP derivatives have been demonstrated to exhibit better chemical stability than bis-PMP ones. PPMP-labeled mixture of twelve monosaccharides (galactosamine, glucosamine, galacturonic acid, glucuronic acid, galactose, glucose/N-acetylgalactosamine, N-acetylglucosamine, xylose, arabinose, mannose, fucose, and rhamnose) has been well separated by a reverse-phase HPLC and detected by on-line ESI-MS method under optimized conditions. The data on characteristic fragment ions of the 13 PPMP-labeled monosaccharides with MS(2) data have been collected. The suggested method exhibits good linearity (correlation coefficients > 0.9975) between the peak areas and the concentration of monosaccharides in a broad concentration range and good reproducibility (RSD < 3.19%). The developed method has been successfully applied to analyze the monosaccharide composition of natural Spirulina polysaccharide SPPB-1.

Trichlorido{2-[2-(η-cyclo-penta-dien-yl)-2-methyl-prop-yl]-1-trimethyl-silyl-1H-imidazole-κN}titanium(IV) tetra-hydro-furan hemisolvate.

The title compound, [Ti(C(15)H(23)N(2)Si)Cl(3)]·0.5C(4)H(8)O, has been prepared from {2-[2-(η(5)-cyclo-penta-dien-yl)-2-methyl-prop-yl]-1H-imidazolyl-κN(1)}bis-(N,N-diethyl-amido-κN)titanium(IV), (C(12)H(14)N(2))Ti(NEt(2))(2), by reaction with excess of Me(3)SiCl in tetra-hydro-furan (THF) at 353 K. The crystal structure contains THF as adduct solvent, disordered around a center of inversion. The presence of THF and the adduct ratio has been independently supported by (1)H NMR spectroscopy. The coordination polyhedron of the Ti atom is distorted square-pyramidal, assuming the cyclo-penta-dienyl (Cp) ring occupies one coordination site. The Ti, Si and CH(2) group C atoms only deviate slightly from the imidazole ring plane [by 0.021 (4), 0.133 (4) and 0.094 (4) Å, respectively]. Comparison of the principal geometric parameters with those of the few known structurally characterized analogues reveal small differences in bond lengths and angles at the Ti atom. The title complex is only stable in THF-d(8) in the presence of excess Me(3)SiCl, otherwise it exists in an equilibrium with equimolar amounts of dichlorido{2-[2-(η(5)-cyclo-penta-dien-yl)-2-methyl-prop-yl]-1H-imidazolyl-κN(3)}titanium(IV) and chloro-trimethyl-silane.

2-[(Cyclo-penta-1,3-dien-2-yl)diphenyl-meth-yl]-1-methyl-1H-imidazole.

The title compound, C(22)H(20)N(2), (Ib), forms along with 2-[(cyclo-penta-1,3-dien-1-yl)diphenyl-meth-yl]-1-methyl-1H-imid-azole, (Ia), which differs with respect to the position of the double-bonds in the C(5)H(5) ring, in an approximately 3:7 ratio (Ia:Ib; NMR spectroscopy data). However, in a single crystal, only compound (Ib) is present. H atoms of the CH(2) group (C(5)H(5) ring) were found from the difference Fourier synthesis and refined isotropically using the riding model. Hypothesis on possible presence of the (Ia) isomer in crystal lattice (model with a C(5)H(5) ring disordered between two positions) was especially checked and rejected due to its inconsistency. In the crystal structure, no significant hydrogen-bonding inter-actions between the CH(2) groups of the C(5)H(5) rings and nonsubstituted N-atoms of the imidazole rings were observed. Despite the fact that the chemically achiral compound (I) crystallizes in a chiral space group P2(1)2(1)2(1), neither the absolute structure determination nor assignment of the inversion twinning was possible in the absence of a heavy atom.

Two 18e Ti(IV) eta5-Cp-tris(sec-amido)-type complexes derived from 1H-imidazol-2-yl side-chain functionalized cyclopentadienes.

Achiral {2-[2-(eta(5)-cyclopentadienyl)-2-methylpropyl]-1H-imidazolyl-kappaN(1)}bis(N,N-diethylamido-kappaN)titanium(IV), [Ti(C(4)H(10)N)(2)(C(12)H(14)N(2))], (I), and closely related racemic (SR)-{2-[(eta(5)-cyclopentadienyl)(phenyl)methyl]-1H-imidazolyl-kappaN(1)}bis(N,N-diethylamido-kappaN)titanium(IV), [Ti(C(4)H(10)N)(2)(C(15)H(12)N(2))], (II), have been prepared by direct reactions of Ti(NEt(2))(4) and the corresponding 1H-imidazol-2-yl side-chain functionalized cyclopentadienes. In compound (II), there are two crystallographically independent molecules of very similar geometries connected by a noncrystallographic pseudosymmetry operation akin to a 2(1) screw axis. All Ti-ligating N atoms in both (I) and (II) are in planar environments, which is indicative of an additional N-->Ti ppi-dpi donation. This fact and the 18e nature of both (I) and (II) are additionally supported by quantum chemical single-point density functional theory (DFT) computations.

(Diethyl ether){1-[2-(1-methyl-1H-imidazol-2-yl-κN)-1,1-diphenyl-ethyl]-(1,2,3,3a,7a-η)-inden-yl}lithium(I).

In the title compound, [Li(C(27)H(23)N(2))(C(4)H(10)O)], the Li atom possesses a nearly planar trigonal coordination environment (assuming the cyclo-penta-dienyl ring of the indenyl group occupies one coordination place). The diethyl ether ligand adopts a nearly planar W-type conformation.