Syntheses, Properties and Photocatalytic Hydrogen Evolution Efficiency of Cyclometalated Pt(Ⅱ) Complexes Bearing S-methylphenyl Group†

doi:10.7503/cjcu20140294

Abstract

Abstract:

Two new ligands 4-(p-thioacetic-S-methylphenyl)-6-phenyl-2,2'-bipyridine[HC^N^NPh·(CH₂SCOCH₃), L3] and 6-(p-thioacetic-S-methylphenyl)-2,2'-bipyridine [HC^N^N(CH₂SCOCH₃), L5] as well as their platinum(Ⅱ) complexes ClPtC^N^N(PhCH₂SCOCH₃)(C3) and ClPtC^N^N·(CH₂SCOCH₃)(C5) were synthesized and characterized by ¹H nuclear magnetic resonance(¹H NMR), electrospray ionization mass spectra(ESI-MS) and X-ray diffraction(XRD) analysis. Photophysical and electrochemical properties of the complexes were studied based on the UV-Vis absorption and emission spectra, excited-state lifetime measurements. It was found that photogenerated hydrogen efficiencies of [ClPtC^N^N(CH₃)(PhCH₃)](C1), [ClPtC^N^N(PhCH₃)](C2), C3, [ClPtC^N^N(CH₃)](C4) and C5 are in accordance with their emission lifetimes, and are arranged in the order C4>C1>C5>C2>C3.

Key words: Thio-polypyridine ligand, Pt(Ⅱ) complex, Photophysical property, Colloidal Pt, Photocatalytic hydrogen production(Ed.: S, Z, M)

CLC Number:

O642
O621

TrendMD:

ZHAO Weiliang, LI Cong, HAN Xu, LI Tingting, ZHANG Guiju, GAN Xin, LI Fumin, FU Wenfu. Syntheses, Properties and Photocatalytic Hydrogen Evolution Efficiency of Cyclometalated Pt(Ⅱ) Complexes Bearing S-methylphenyl Group^†[J]. Chem. J. Chinese Universities, 2014, 35(10): 2214.

Figures/Tables 8

Fig.1 Chemical structures of ligands L1—L5(A) and their corresponding Pt(Ⅱ) complexes C1—C5(B)

Table 1 Selected crystallographic data and collection parameters for complex C3*

Formula	C₂₅H₁₉ClN₂OPtS	V/nm³	4.2972(15)
Formula weight	626.02	Z	8
T/K	113(2)	D_c/(g·cm^-3)	1.935
Crystal size	0.08 mm×0.06 mm×0.06 mm	2θ_max/(°)	50.04
Crystal system	Orthorhombic	μ/mm^-1	6.733
Space group	Pbca	Reflections collected/unique	26865/3787
a/nm	1.0302(2)	Parameter	290
b/nm	1.5959(3)	R_int	0.0768
c/nm	2.6136(5)	Goodness of fit	1.053
α/(°)	90.00	R₁, wR₂(all data)	0.0454, 0.0874
β/(°)	90.00	R₁, wR₂[I>2σ(I)]	0.0338, 0.0805
γ/(°)	90.00	Residual electron density/(e·nm^-3)	-1492/1567

Table 2 Selected bond lengths(nm) and bond angles(°) for complex C3

Pt1—N2	0.1940(3)	Pt1—C16	0.2032(4)
Pt1—N1	0.2083(3)	Pt1—Cl1	0.2307(1)
N2—Pt1—C16	81.3(2)	C16—Pt1—N1	161.2(2)
N2—Pt1—N1	80.0(1)	N2—Pt1—Cl1	179.2(1)
C5—N1—Pt1	113.0(3)	C10—N2—Pt1	118.6(3)
C1—N1—Pt1	128.2(3)	C6—N2—Pt1	119.4(3)

Fig.2 ORTEP view of complex C3 with atom labeling scheme Perspective view with thermal ellipsoids at 30% probability and hydrogen atoms are omitted for clarity.

Fig.3 Absorption spectra of complexes C1—C5 in CH3CN(4.4×10-5 mol/L) a. C1; b. C2; c. C3; d. C4; e. C5.

Fig.4 Normalized emission spectra of complexes C1—C5 in CH3CN(λex=365 nm) a. C1; b. C2; c. C3; d. C4; e. C5.

Table 3 Photophysical data and electrochemical properties of complexes C1—C5

Complex	$λ abs a$ /nm[ε/(mol^-1·dm³·cm^-1)]	λ_em/nm	$τ 0 b$ /ns	Oxidation $E pa c$ /V	Reduction $E pc c$ /V
C1	293(27682), 332(14068), 424(3250)	563	145	1.01	-0.83, -1.32
C2	286(30636), 329(16885), 426(3285)	533	59	0.99	-0.86, -1.35
C3	286(31794), 329(14983), 426(3289)	559	50	0.85	-0.89
C4	276(35159), 328(14045), 420(2181)	567	151	1.06	-0.80, -1.33
C5	278(31272), 327(13575), 419(1800)	556	69	1.06	-0.78, -1.35

Table 3 Photophysical data and electrochemical properties of complexes C1—C5

Complex	$λ abs a$ /nm[ε/(mol^-1·dm³·cm^-1)]	λ_em/nm	$τ 0 b$ /ns	Oxidation $E pa c$ /V	Reduction $E pc c$ /V
C1	293(27682), 332(14068), 424(3250)	563	145	1.01	-0.83, -1.32
C2	286(30636), 329(16885), 426(3285)	533	59	0.99	-0.86, -1.35
C3	286(31794), 329(14983), 426(3289)	559	50	0.85	-0.89
C4	276(35159), 328(14045), 420(2181)	567	151	1.06	-0.80, -1.33
C5	278(31272), 327(13575), 419(1800)	556	69	1.06	-0.78, -1.35

Fig.5 Hydrogen production from system containing TEOA(2.2×10-2 mol/L), complexes C1—C5(4.4×10-5 mol/L) and colloidal Pt(8.7×10-5 mol/L) with CH3CN/H2O(1∶1, volume ratio) as the solvent at pH=7.5 upon irradiation(λ>390 nm) TONs are calculated based on the Pt(Ⅱ) photosensitizer. (A) Without MV2+; (B) with MV2+.

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