红外与拉曼光谱 案例教学

Table 1.8 Results for FT-IR and Raman spectra of hydrated alkali tetraborates (cm-1)

Rb2Ca[B4O5(OH)4]2·8H2O FT-IR Raman

Cs2Ca[B4O5(OH)4]2·8H2O FT-IR Raman

K2Sr[B4O5(OH)4]2·10H2O FT-IR Raman

Rb2[B4O5(OH)4]·3.6H2O FT-IR Raman

Cs2[B4O5(OH)4]·3H2O FT-IR Raman 3608.41m 3358.55bvw 3200.00bw

3603.61m 3549.97m 3348.89bw 3147.69bw

Assignment

3614.72s 3611.71s 3614.28s 3611.90s 3488.89bw 3588.32s 3598.33m 3593.65m 3439.92w 3443.02bw 3439.22w 3465.40bw 3293.33bm 3434.93s 3362.13bw 3533.16m 3319.61vw 3275.19vw 3296.30vw 3293.58vw 3207.41bw 3185.72bvw 3200.00vw 3210.47vw 3185.19vw 3200.23vw 2607.41vw 2597.95vw 2592.20m 2437.04vw 2442.35vw 2406.00bvw 2429.63bvw 2359.95vw 2363.63vw 1680.45m 1669.76m 1653.55m 1678.52w 1632.61m 1629.02m 1645.47w 1453.70bw 1432.58bw 1423.00bm 1453.94bvw 1345.45m 1349.68m 1343.71m 1350.89m 1348.42m 1341.42m 1290.39w 1282.68w 1249.83bw 1232.63bm 1264.67w 1229.34w 1152.03m 1147.94bm 1157.98bm 1148.61bm 1125.39w 1120.55w 1067.94w 1063.55w 1052.35bvw 1050.35bvw 1001.76m 1021.45bw 1001.57m 1004.08bw 999.93s 1000.50s 998.45m 945.22s 943.11w 943.04s 940.45w 943.55vs 940.55vs 941.71w 833.08m 831.06m 828.30s 825.33s 830.55bw 772.68m 770.95m 781.08m 771.38m 707.90m 703.00m 707.69m 706.70w 659.06bm 661.92bw 680.83w 606.93bw 653.56w 590.92bm 576.47vw 586.47bw 576.71vw 572.26bw 573.45s 566.28w 568.26vs 532.05m 530.06m 518.22w 519.33m 464.09m 461.75m 464.20m 576.71vw 459.66m 458.12m b=broad m=middle s=strong v=very w=weak, B(3)-O means three coordinate boron; B(4)-O means four coordinate boron

ν(O-H)

2585.19w 2432.65bw

1646.75bm 1457.50m 1342.51m 1220.35bm 1143.37bm

1344.38bw

δ(H-O-H)

νas(B3-O)

1050.80w 998.64m 939.30vs 819.42s

1002.54m 938.83w

δ(BO-H)

νas(B4-O)

νs(B3-O)

712.39 668.53m 640.18w

518.24w 462.84m

771.10m

572.03vs

459.83m

νs(B4-O)

γ(B3-O)

νp(tetraborate anion)

δ(B4-O)

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1.3.3. Pentaborate

Infrared and Raman spectra of Rb[B5O6(OH)4]?2H2O and Cs[B5O6(OH)4]?2H2O

are shown in Fig.3 and 4, respectively, and the band assignments are listed in Table 3. The [B5O6(OH)4]- consists of a central BO4 tetrahedral with two opposite

tetrahedral edges shared with B2O3(OH)2 groups. A series of borate compounds M[B5O6(OH)4]?xH2O(M=Li,Na,K,Rb,Cs and NH4) reported are isotypic or homeotypic. IR and Raman spectra of Rb[B5O6(OH)4]?2H2O and Cs[B5O6(OH)4]?2H2O are similar to those of M[B5O6(OH)4]?xH2O(M=Li,Na,K and NH4). The characteristic peaks of infrared spectra of borates containing pentaborate anion [B5O6(OH)4]- exhibit at around 1090,1025,925,780 and 690cm-1. In the Raman spectra, the very sharp strong band observed at 550cm-1 is assigned to the pulse vibration of pentaborate anion [B5O6(OH)4]- according to the work of Janda and Heller[9]. The middle band at 914.81(905.76) and 764.57(767.48)cm-1 is characteristic for the symmetric stretching modes of B3-O and B4-O, respectively. Two weak bands observed at 507.51(503.57) and 454.61(459.59)cm-1 are attributed to the bending modes of B4-O.

Wavenumber(cm-1) Fig.1.3 FT-IR spectra of pentaborates A: Cs[B5O6(OH)4]·2H2O B: Rb[B5O6(OH)4]·2H2O Raman shift(cm-1) Fig.1.4 Raman spectra of pentaborates A: Cs[B5O6(OH)4]·2H2O B: Rb[B5O6(OH)4]·2H2O

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Table 1.9 Results for FT-IR and Raman spectra of hydrated pentaborates (cm-1)

Assignment

FT-IR Raman FT-IR Raman 3442.07s 3441.74s 3390.06s 3083.99s 3075.05m 3131.00s 3121.61s ν(O-H) 2454.80m 2420.88m 2167.79w 2189.15w 1647.77m 1642.71m δ(H-O-H) 1427.25bvw 1488.15w 1430.95bvw 1474.28w νas(B3-O) 1357.62bvw 1363.61bvw 1238.18m 1219.35m δ(BO-H) 1087.40s 1085.69w 1077.64m 1063.57w νas(B4-O) 1023.38m 1023.57m 922.95s 914.81m 925.11s 905.76m νs(B3-O) 780.82s 785.69w 779.64s νs(B4-O) 745.50w 764.57m 747.51m 767.48m 691.05s 691.66s 639.94m 637.85w γ(B3-O) 597.00w 609.00w 553.31vs 542.84m 547.81vs νp(hexaborate anion) 501.24m 507.51w 501.12m 503.57w δ(B4-O) 457.94m 454.61w 457.94m 459.59w

b=broad m=middle s=strong v=very w=weak, B3-O means three coordinate boron; B4-O means four coordinate boron Rb[B5O6(OH)4]?2H2O

Cs[B5O6(OH)4]?2H2O

1.3.4. Hexaborate and triborate

Infrared and Raman spectra of two alkali cobalt hexaborates and one triborate are shown in Fig.5 and 6, respectively, and the band assignments are listed in Table 4.

The [B6O7(OH)6]2- ion contains three triangular and three tetrahedral boron group and is unique in that one oxygen atom is common to all three rings. The hexaborate K2Co[B6O7(OH)6]2·4H2O is isotypic with Rb2Co[B6O7(OH)6]2·4H2O and their vibrational spectra show very similar. For each band found in the spectrum of K2Co[B6O7(OH)6]2·4H2O a corresponding band is observed in the Rb2Co[B6O7(OH)6]2·4H2O with frequencies differing at most by +4cm-1. Infrared spectra of alkali cobalt hexaborate occur in range 3500 to 3100cm-1 because of hydrogen bonding, with decreasing strength going towards lower frequencies, and the middle band at 1641.66(1639.51)cm-1 is related to H-O-H bonding mode. The three weak peaks at 1443.75(1443.35), 1412.87(1412.18) and 1363.89(1362.77)cm-1 are attributed to the asymmetric stretching modes of B3-O. Two alkali cobalt hexaborates show two sharp characteristic bands at 947.61(945.28) and 809.39(805.15) cm-1, and those peaks are assigned as the symmetric stretching modes of B3-O and B4-O,

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respectively. In the Raman spectra, the strong band observed at 620.19(616.79)cm-1 are assigned to the symmetric pulse vibration of hexaborate anion. Compared with alkaline-earth metal borates reported by Li Jun, infrared and Raman spectra of alkali cobalt hexaborates show a resemblance to those of alkaline-earth metal borates and the difference lies in the shifting of bands.

The triborate K3[B3O4(OH)4]2·2H2O was built up from six-membered rings formed from alternate boron and oxygen by concern sharing among two BO4 tetrahedral and one BO3 triangle. Infrared and Raman spectra of this compound is similar to those of hydrated potassium(rubidium) cobalt hexaborate because the structure of hydrated triborate K3[B3O4(OH)4]·2H2O also contains six-membered rings. In addition, it is noted that the symmetric pulse vibration of triborate and hexaborate anions is closed to 620cm-1.

Wavenumber(cm-1) Fig.1.5 FT-IR spectra of borates A: K3[B3O4(OH)4]·2H2O B: Rb2Co[B6O7(OH)6]2?4H2O C: K2Co[B6O7(OH)6]2?4H2O Raman shift(cm-1) Fig.1.6 Raman spectra of borates A: K3[B3O4(OH)4]·2H2O B: Rb2Co[B6O7(OH)6]2?4H2O C: K2Co[B6O7(OH)6]2?4H2O 12