[Preliminary Study on the Unique Spectroscopic Characteristics of Natural and Synthetic Diamonds].

A systematic comparative study on the natural diamond, the natural diamond treated by heat or irradiation and synthetic diamond prepared by chemical vapor deposition (CVD) or High temperature and high pressure (HTHP) were carried out by UV-Vis-NIR absorption and FTIR spectra. The results showed that: natural diamond, treated natural samples such as irradiated or annealed ones under high temperature and the HTHP synthetic diamond, the reflection coefficient is obviously variation between 200 nm and 1100 nm in UV-Vis-NIR spectra of above samples. In contrast, the reflection coefficient of CVD synthetic diamond is relatively smaller than the former. Infrared spectra showed that synthetic diamonds, especially for CVD synthetic diamonds have no obvious absorption peak between 800 and 1 600 cm(-1). In additional, the results of DiamondView detection are different for different kinds of diamonds. Generally speaking, some CVD synthetic diamonds treated by HTHP appears some parallel dislocation lines, and show light-blue fluorescence. HPHT synthetic diamonds exhibit strong blocky geometrical shapes whereas some natural diamonds exhibit more tree-ring type fluorescence patterns, the color of diamonds' fluorescence image may change after treated by HTHP or irradiation. In a word, in view of the diversity and innovation of the synthesis technologies for diamond, the natural and synthetic diamonds have some similar spectra characteristic in term of UV-Vis-NIR and FTIR spectra, some special natural diamonds without typical spectra characteristic of natural ones need to be further supplemented with DiamondView, photoluminescence spectra and other instruments.

[The unique reflection spectra and IR characteristics of golden-color seawater cultured pearl].

A comparative study on the natural-color golden seawater cultured pearls and the treated-color golden seawater cultured pearls were carried out by UV-Vis reflectance spectra. Furthermore, the frequency variations of v3, v1 , v2 and v4 bands of the aragonites (a crystal form of calcium carbonate) with the positions of nacreous layer and nucleus in natural or treated-color golden-color seawater cultured pearls were firstly systematically measured. The results showed that: (1) based on the results of UV-Vis reflectance spectra of natural or treated-color golden seawater cultured pearls, interestingly, it was firstly found that the natural-color golden one displays slight varied UV-Vis reflection spectra because of its different surface microstructure located on the outer nacreous layer. Meanwhile, according to the characteristic of UV-Vis reflectance spectra of treated-color golden ones, the treated-color ones were firstly classified to four categories. (2) The frequency of v2 band of aragonite in nacreous layer of natural-color or treated-color golden pearls was greater than the other one from theirs corresponding nucleus, namely A clear blue shift was observed in the former. But the other bands were not altered in the positions of nacreous layer and nucleus, and had the same valves with synthetic aragonites. Additionally, the location of absorption bands of aragonite in nacreous layer of natural or treated-color golden pearls had no frequency shift, which indicates that the behavior of color-treating had no effect on the crystal structure of golden pearls.

(E)-Ethyl N'-(3-hy-droxy-benzyl-idene)hydrazinecarboxyl-ate dihydrate.

The asymmetric unit of the title compound, C(10)H(12)N(2)O(3)·2H(2)O, contains two organic mol-ecules with similar conformations and four water mol-ecules. Each organic mol-ecule is close to planar (r.m.s. deviations = 0.035 and 0.108 Å) and adopts a trans conformation with respect to its C=N bond. In the crystal, the components are linked into a three-dimensional network by N-H⋯O, O-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds, some of which are bifurcated. An R(2) (2)(8) loop occurs between adjacent organic mol-ecules.

(E)-Methyl N'-(3-hy-droxy-benzyl-idene)hydrazinecarboxyl-ate dihydrate.

The title compound, C(9)H(10)N(2)O(3)·2H(2)O, crystallizes with two organic mol-ecules and four water mol-ecules in the asymmetric unit. Both organic mol-ecules adopt a trans conformation with respect to the C=N bond and are close to planar [dihedral angles between the side chain and the aromatic ring = 9.34 (8) and 4.96 (8)°]. In the crystal, the components are linked into three-dimensional network by N-H⋯O and O-H⋯O hydrogen bonds.

(E)-Methyl N'-[(1H-indol-3-yl)methyl-idene]hydrazinecarboxyl-ate 0.25-hydrate.

The asymmetric unit of the title compound, C(11)H(11)N(3)O(2)·0.25H(2)O, contains two independent organic mol-ecules and a water mol-ecule, which lies on a twofold rotation axis. The side chains of the two mol-ecules have slightly different orientations, the C=N-N-C torsion angle being -163.03 (15)° in one and -177.52 (14)° in the other, with each adopting a trans configuration with respect to the C=N bond. In the crystal, mol-ecules are linked into chains extending along b by N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds and in addition, four inter-molecular C-H⋯π inter-actions are present.

(E)-Methyl N'-(2,4,5-trimeth-oxy-benzyl-idene)hydrazinecarboxyl-ate.

The title mol-ecule, C(12)H(16)N(2)O(5), adopts a trans configuration with respect to the C=N bond. In the crystal, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into chains in [001], and weak inter-molecular C-H⋯O inter-actions further link the chains into corrugated layers parallel to the bc plane.

N'-(4-Hydr-oxy-3-methoxy-benzyl-idene)acetohydrazide monohydrate.

In the title compound, C(10)H(12)N(2)O(3)·H(2)O, the Schiff base mol-ecule is approximately planar [within 0.189 (1) Å]. The inter-planar angle between the benzene and acetohydrazide planes is 8.50 (10)°. In the crystal, mol-ecules are linked into a three-dimensional network by strong and weak O-H⋯O and strong N-H⋯O hydrogen bonds. The hydr-oxy H atom deviates from the 4-hydr-oxy-3-methoxy-phenyl mean plane by 0.319 (2) Å, probably due to the involvement of this H atom in the O-H⋯O hydrogen bond. The weak O-H⋯O hydrogen bond is involved in a bifurcated hydrogen bond with R(1) (2)(4) motif. A weak C-H⋯π inter-action is also present.

N'-(3,4-Dihydroxy-benzyl-idene)acetohydrazide.

In the title compound, C(9)H(10)N(2)O(3), the Schiff base mol-ecule is approximately planar, the dihedral angle between the benzene ring and the acetohydrazide group (r.m.s. deviation = 0.034 Å) being 8.81 (7)°. An intra-molecular O-H⋯O hydrogen bond is observed. In the crystal, mol-ecules are linked into a three-dimensional network by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds.

N'-[4-(Dimethyl-amino)benzyl-idene]acetohydrazide.

The title compound, C(11)H(15)N(3)O, crystallizes with two independent mol-ecules per asymmetric unit which differ slightly in their side-chain orientations: the C=N-N-C torsion angle is -176.2 (3)° in one of the mol-ecules and -179.83 (3)° in the other. Each independent mol-ecule adopts a trans configuration with respect to the C=N bond. The two independent mol-ecules are related by a pseudo-inversion center and they exist as a N-H⋯O hydrogen-bonded dimer. The dimers are linked into zigzag chains along [100] by C-H⋯O hydrogen bonds.

(E)-Methyl N'-(3-methoxy-benzyl-idene)hydrazinecarboxyl-ate.

The title compound, C(10)H(12)N(2)O(3), crystallizes with two independent mol-ecules in the asymmetric unit which differ in the orientation of the meth-oxy group. Each independent mol-ecule adopts a trans configuration with respect to the C=N bond. In the crystal structure, mol-ecules are linked into chains running along [001] by N-H⋯O and N-H⋯N hydrogen bonds. In addition, an inter-molecular C-H⋯π inter-action is observed.

N'-(2-Furylmethyl-ene)acetohydrazide.

In the title mol-ecule, C(7)H(8)N(2)O(2), the acetohydrazide group is planar within 0.014 (2) Šand forms a dihedral angle of 5.35 (8)° with the furan ring. The mol-ecule adopts a trans configuration with respect to the C=N bond. In the crystal, molecules are linked into a chain along the a axis by N-H⋯O hydrogen bonds.

(E)-Methyl N'-(2-hydr-oxy-3-methoxy-benzyl-idene)hydrazinecarboxyl-ate.

The title compound, C(10)H(12)N(2)O(4), adopts a trans configuration with respect to the C=N double bond. The non-H atoms of the mol-ecule are essentially coplanar, with a maximum deviation of 0.015 (2) Å. An intra-molecular O-H⋯N inter-action is observed. In the crystal structure, the mol-ecules are linked into a two-dimensional network parallel to the ac plane by N-H⋯O hydrogen bonds involving the meth-oxy O atom and by two C-H⋯O hydrogen bonds involving the carbonyl O atom. In addition, an intermolecular C-H⋯π inter-action is observed.

Ethyl (E)-2-(2-furyl-idene)hydrazine-carboxyl-ate.

In the title compound, C(8)H(10)N(2)O(3), the hydrazinecarboxyl-ate group is twisted from the furan ring by 6.98 (17)°. In the crystal, the mol-ecules are linked into one-dimensional chains running along the c axis by N-H⋯O hydrogen bonds.

Methyl 2-[(E)-3-hydr-oxy-4-methoxy-benzyl-idene]hydrazinecarboxyl-ate.

The title compound, C(10)H(12)N(2)O(4), adopts a trans configuration with respect to the C=N bond. The hydrazinecarboxyl-ate group is twisted from the benzene ring by 6.62 (5)° and an intramolecular O-H⋯O hydrogen bond occurs. In the crystal structure, mol-ecules are linked into a two-dimensional network parallel to (100) by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds. In addition, weak C-H⋯π inter-actions are observed.

Methyl (E)-N'-[1-(2,4-dihydroxy-phen-yl)ethyl-idene]hydrazinecarboxyl-ate.

The mol-ecule of the title compound, C(10)H(12)N(2)O(4), adopts a trans configuration with respect to the C=N bond. The dihedral angle between the benzene ring and the methyl hydrazinecarboxyl-ate plane is 3.01 (6)°. An intra-molecular O-H⋯N hydrogen bond is observed. In the crystal, mol-ecules are linked into a two-dimensional network parallel to (10) by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds.

N'-(3,4-Dihydroxy-benzyl-idene)acetohydrazide monohydrate.

In the title compound, C(9)H(10)N(2)O(3)·H(2)O, the Schiff base mol-ecule is approximately planar, the dihedral angle between the benzene and acetohydrazide planes being 5.40 (7)°. An intra-molecular O-H⋯O hydrogen bond is observed. In the crystal, mol-ecules are linked into a two-dimensional network parallel to (100) by O-H⋯O, N-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds, and by π-π inter-actions between symmetry-related benzene rings [centroid-centroid distance = 3.543 (2) Å].

N'-(3,4-Dimethoxy-benzyl-idene)aceto-hydrazide.

The asymmetric unit of the title compound, C(11)H(14)N(2)O(3), contains two independent mol-ecules with close conformations; the C=N-N-C torsion angle is 176.4 (1)° in both mol-ecules. In the crystal, inter-molecular N-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into chains running along the [01] direction.

N'-(3,4-Dimethoxy-benzyl-idene)acetohydrazide.

In the title mol-ecule, C(11)H(14)N(2)O(3), the acetohydrazide group is planar 0.084 (1) Šand forms a dihedral angle of 19.7 (1)° with the benzene ring. One of the meth-oxy groups is coplanar with the attached benzene ring within 0.052 (3) Å, whereas the other is slightly twisted [C-O-C-C = 6.3 (3)°]. The mol-ecule adopts a trans configuration with respect to the C=N bond. In the crystal, the mol-ecules are linked into chains along the a axis by N-H⋯O hydrogen bonds and the chains are cross-linked into a three-dimensional network by C-H⋯O hydrogen bonds.

N'-(3-Methoxy-benzyl-idene)aceto-hydrazide.

In the title mol-ecule, C(10)H(12)N(2)O(2), the acetohydrazide group is planar within 0.012 (1) Šand forms a dihedral angle of 5.25 (8)° with the benzene ring. The meth-oxy group is coplanar with the attached benzene ring [C-O-C-C = 0.1 (2)°]. The mol-ecule adopts a trans configuration with respect to the C=N double bond. In the crystal, mol-ecules are linked into centrosymmetric dimers by N-H⋯O hydrogen bonds and these dimers are linked into a ribbon-like structure along [110] by C-H⋯O hydrogen bonds. In addition, an inter-molecular C-H⋯π inter-action is observed.

N'-(4-Hydroxy-benzyl-idene)aceto-hydrazide monohydrate.

In the title compound, C(9)H(10)N(2)O(2)·H(2)O, the mol-ecular skeleton of the acetohydrazide mol-ecule is nearly planar [within 0.014 (1) Å]. The mol-ecule adopts a trans configuration with respect to the C=N bond, while the side chain is slightly twisted away from the attached ring, forming a dihedral angle of 9.975 (8)°. The crystal packing exhibits a three-dimensional network composed from alternating acetohydrazide mol-ecules and uncoordinated water mol-ecules, which inter-act via N-H⋯O, O-H⋯O and O-H⋯N hydrogen bonds. A C-H⋯π inter-action is also present.