甲苯溶液中轴向含三苯基膦的硝基钴（III）四苯基卟啉的结构与光化学

Structure and photochemistry of nitrocobalt(III) tetraphenylporphyrin with axial triphenylphosphine in toluene solutions.

作者信息

Adachi Haruna, Suzuki Hiroyuki, Miyazaki Yoshio, Iimura Yasuhiro, Hoshino Mikio

机构信息

The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan.

出版信息

Inorg Chem. 2002 May 6;41(9):2518-24. doi: 10.1021/ic0108686.

DOI:10.1021/ic0108686

PMID:11978120

Abstract

Thermal and photochemical reactions of nitroaquacobalt(III) tetraphenylporphyrin, (NO(2))(H(2)O)Co(III)TPP, have been investigated in toluene solutions containing triphenylphosphine, P phi(3). It is found that Pphi(3) thermally abstracts an oxygen atom from the NO(2) moiety of (NO(2))(H(2)O)Co(III)TPP with a rate constant 0.52 M(-1) s(-1), resulting in the formation of nitrosylcobalt porphyrin, (NO)CoTPP. The 355-nm laser photolysis of (NO(2))(H(2)O)Co(III)TPP at low concentrations of P phi(3) (<1.0 x 10(-4) M) gives Co(II)TPP and NO(2) as intermediates. The recombination reaction of Co(II)TPP and NO(2) initially forms the coordinately unsaturated nitritocobalt(III) tetraphenylporphyrin, (ON-O)Co(III)TPP, which reacts with P phi(3) to yield nitro(triphenylphosphine)cobalt(III) tetraphenylporphyrin, (NO(2))(P phi(3))Co(III)TPP. Subsequently, the substitution reaction of the axial P phi(3) with H(2)O leads to the regeneration of (NO(2))(H(2)O)Co(III)TPP. From the kinetic studies, the substitution reaction is concluded to occur via a coordinately unsaturated nitrocobalt(III) porphyrin, (NO(2))Co(III)TPP. At higher concentrations of P phi(3) (>4 x 10(-3) M), (NO(2))(H(2)O)Co(III)TPP reacts with P phi(3) to form (NO(2))(P phi(3))Co(III)TPP: the equilibrium constant is obtained as K = 4.3. The X-ray structure analysis of (NO(2))(P phi(3))Co(III)TPP reveals that the P-Co-NO(2) bond angle is 175.0(2) degrees and the bond length Co-NO(2) is 2.000(7) A. In toluene solutions of (NO(2))(H(2)O)Co(III)TPP containing P phi(3) (>4 x 10(-3) M), the major light-absorbing species is (NO(2))(P phi(3))Co(III)TPP, which yields (NO)CoTPP by continuous photolysis. The laser photolysis of (NO(2))(P phi(3))Co(III)TPP gives Co(II)TPP, NO(2), and P phi(3) as initial products. The NO(2) molecule is suggested to be reduced by P phi(3) to yield NO, and the reaction between NO and Co(II)TPP gives (NO)CoTPP. The quantum yield for the photodecomposition of (NO(2))(P phi(3))Co(III)TPP is determined as 0.56.

摘要

在含有三苯基膦（Pφ₃）的甲苯溶液中，对硝基水合钴（III）四苯基卟啉（(NO₂)(H₂O)Co(III)TPP）的热反应和光化学反应进行了研究。发现Pφ₃能从(NO₂)(H₂O)Co(III)TPP的NO₂部分热夺取一个氧原子，速率常数为0.52 M⁻¹ s⁻¹，生成亚硝酰钴卟啉（(NO)CoTPP）。在低浓度Pφ₃（<1.0×10⁻⁴ M）下，(NO₂)(H₂O)Co(III)TPP的355 nm激光光解产生Co(II)TPP和NO₂作为中间体。Co(II)TPP与NO₂的重组反应最初形成配位不饱和的亚硝酸根钴（III）四苯基卟啉（(ON - O)Co(III)TPP），它与Pφ₃反应生成硝基（三苯基膦）钴（III）四苯基卟啉（(NO₂)(Pφ₃)Co(III)TPP）。随后，轴向的Pφ₃被H₂O取代反应导致(NO₂)(H₂O)Co(III)TPP再生。通过动力学研究得出，取代反应是通过配位不饱和的硝基钴（III）卟啉（(NO₂)Co(III)TPP）发生的。在较高浓度Pφ₃（>4×10⁻³ M）下，(NO₂)(H₂O)Co(III)TPP与Pφ₃反应形成(NO₂)(Pφ₃)Co(III)TPP：得到平衡常数K = 4.3。(NO₂)(Pφ₃)Co(III)TPP的X射线结构分析表明，P - Co - NO₂键角为175.0(2)°，Co - NO₂键长为².000(7) Å。在含有Pφ₃（>4×10⁻³ M）的(NO₂)(H₂O)Co(III)TPP的甲苯溶液中，主要的吸光物种是(NO₂)(Pφ₃)Co(III)TPP，通过连续光解产生(NO)CoTPP。(NO₂)(Pφ₃)Co(III)TPP的激光光解产生Co(II)TPP、NO₂和Pφ₃作为初始产物。推测NO₂分子被Pφ₃还原生成NO，NO与Co(II)TPP反应生成(NO)CoTPP。(NO₂)(Pφ₃)Co(III)TPP光分解的量子产率测定为0.56。