UV-Vis absorption spectroscopy performs qualitative and quantitative analysis and structural characterization through studying the absorption by molecules or ions of radiant energy in the UV and visible spectrum region. It

reflects the transition between the energy level of electrons in molecules. Molar ratio is n (OTP): n (As³⁺) = 2:1 (Figure 1), 4:1 (Figure 2), 6:1 (Figure 3).

UV-Vis spectrum detects changes of peak in conjugated system. Coordination numbers changes after the complexing of OTP and OTP-As while conjugation system remains the same. In this way UV-Vis spectrum

strongly proofs the number of moles of OTP has little influence on coordination structure of arsenic ion.

Figure 1, Figure 2 and Figure 3 shows that UV-vis absorption peak of OTP-As is not affected by different ratio of n (OTP) to n (As³⁺), the maximum value of which is in the vicinity of 267.50 nm and 220 nm shown in Table 2. Comparing three UV graphs, the maximum absorption peak wavelength is almost the same, which shows that the conjugated system is similar; it means the number of moles of OTP has little influence on coordination structure of arsenic ion and all of the complex is double-coordinated.

Infrared spectroscopy identifies compounds and determines molecular structure through collecting information about atomic relative vibration and molecular vibration information. FTIR spectrum of Figure 4. OTP-As of which the molar ratio is n (OTP):n (As³⁺) = 2:1. FTIR spectrum of Figure 5. OTP-As of three kinds of different molar ratio of n (OTP):n (As³⁺) = 2:1, 4:1, 6:1 as shown in.

The molecular vibration frequency is proportional to the group binding constant K 1/2, so when the binding force constant reduces, λ value approximates lower wave number. Figure 5 shows that the infrared feature information isomers are almost the same. Although OTP-As is a mixture, they have the same functional group and the structure is similar. Different ratio of n (OTP):n (As³⁺) does not exert much influence on infrared characteristic absorption peak of OTP-As. The structural information of the FTIR spectrum Figure 5 is consistent with that of UV spectrum.

Molecular fluorescence analysis is a quantitative method based on fluorescence intensity of material. The complexes determined by this experiment were A= (EGC)₂As or (ECG)₂As, B= (EGCG)₂As, C= (EC)₂As [the molar ratio n (OTP):n (As³⁺) = 2:1, 4:1, 6:]">1]. Experiment results show that λ value in fluorescence spectrum of OTP-As of different complexes with different concentrations is similar but the fluorescence intensity is different (Figure 6, Figure 7). We can see that EX wavelength is about 257.0 nm when OTP-As complexes are in excited state while EM wavelength is about 591.1 - 593.7.0 nm when they are in launching state. The higher the concentration of the solution is, the stronger INT intensity is. Because of the dilute concentration, when excited light intensity is constant, fluorescence intensity is proportional to the concentration of fluorescent matter—F = K × C [13] . Analyze Figure 7 we can see that maximum peak of EM graph often complex was at wavelength λ = 591.0 nm; and the higher concentration of the solution is, the stronger the intensity of EM is.

Figure 7 shows that EX spectrum (excited) λ 200 - 400 nm of OTP-As complexes of the same proportion are almost the same, the maximum peak wavelength λ nearly overlap; but their EM spectra (emission) intensity of 500 - 650 nm differentiates significantly. The increasing of the molecular conjugated structure system and the molecular plane rigidity reduce the molecular vibration, along with the interaction between the molecule and the solvent or other solute molecules, meaning external transfer loss of molecular energy in excited state reduces and favors fluorescence emission. And the increase of rigid plane can enlarge the absorption cross section of molecules, molar absorption coefficient, and fluorescence intensity. Because the larger the non-local area of π electron is, the easier it is to be excited; and molecular fluorescence efficiency will also enhances. In addition, electron-donating groups such as -OH, -OR increase the transition probability between the lowest excited singlet and ground state; and often intensify the fluorescence, λ moves to long wavelength side. Compare A, B, C curve in Figure 7, the wavelength corresponding to their maximum peak is slightly different; B curve stands for (EGCG)₂As, of which the maximum peak wavelength is 593.7 nm. Conjugation degree increases because of a lot of free phenol -OH. And since molecular weight of the complex was large, solubility low, concentration low, EM intensity was low. But the wavelength corresponding to the maximum peak of A, C curve were the same, and EM intensity of Curve A is obviously weaker than that of Curve C. Presumably it stands for (EGC)₂As or (ECG)₂As. Because free phenol -OH in molecules reduced, fluorescence λ became a bit smaller as 591.1 nm,

the solubility of the molecules is slightly enhanced; and solution concentration is quite high; the EM intensity was stronger than that of Curve B. Curve C stands for (EC)₂As, fluorescence λ is 590.3 nm, minimum molecular weight, high solubility and high concentration, all of which led to great EM intensity. In Table 3, EM spectrum revealed information about 5 kinds of OTP-As mixture generating different complex. [note] A, B, C respectively stand for 2:1, 4:1, 6:1 OTP-As dissolved in 60 mL 95% ethanol solution.

X ray is a kind of electromagnetic radiation generated by electron beam bombarding elements in the X ray tube. X-ray diffraction is an effective means of analyzing crystal structure for diffraction peak intensity and half peak width reflects amorphous degree of powder and changing information of lattice. In Table 4, 2θ stands for diffraction, D crystal grain size, B half peak width. Figure 8 is XRD for OTP-As.

According to test data in Figure 8, diffraction peak of λ/nm = 21.401 is the strongest, which shows OTP-As is polycrystal mixture. Information provided by Figure 8 XRD indicates that OTP-As is mixture.

Basing on substance’s selective absorption of light, Spectrophotometric analysis method can not only determine most inorganic ions but many organic compounds. It can not only be used as quantitative analysis but also qualitative analysis for some organic compounds and determination of physical and chemical constant as well as the composition of complex. Table 5 shows photometric value of OTP-As of different mass dissolved in 60 mL 95%

ethanol solution. Figure 9 shows that absorbance of the same substance increases along with concentration and absorbance of OTP-As synthesized under the condition of n (OTP):n (As³⁺) was = 2:1 increases along with the decrease of wavelength.

In Table 6, X stands for group of proton peaks. The whole spectrum indicates that in addition to the quite

large mass peak shift of benzene ring, proton peaks of were stronger than OTP-As, most

of the rest were repeated display.

Comparison of ¹H-NMR between OTP and OTP-As manifests that after OTP-polyol-complexed with As³⁺, ¹H-NMR-OH peaks in aromatic ring of Ph-OH shifted from 5.446 - 5.953 (quart) to 5.231 - 5.753 (quart); other -OH peaks shifted from 3.043 (OH) to 3.116 (OH). The obvious shift suggests that As³⁺ has already complexed with OTP and OTP-As was produced.