Strength of the Zn-N Coordination Bond in Zinc Porphyrins on the Basis of Experimental Thermochemistry
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- 作者：Rodrigo Patiñ ; o ; Myriam Campos ; Luis Alfonso Torres
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：October 29, 2007
- 年：2007
- 卷：46
- 期：22
- 页码：9332 - 9336
- 全文大小：70K
- 年卷期：v.46,no.22(October 29, 2007)
- ISSN：1520-510X
文摘
The compound, 5,10,15,20-tetrakis(4-methoxyphenyl)porphine zinc(II) (ZnTMPP), was prepared, and its thermochemical properties were experimentally established. The standard molar energy of combustion (cUm) wasdetermined from oxygen rotating-bomb combustion calorimetry experiments. The standard molar enthalpies ofcombustion (cHm) and formation (fHm) were derived. The enthalpy of sublimation (crgHm) was determinedby Knudsen effusion at high temperatures. With these results, the standard molar enthalpies of formation andatomization (atHm) in the gas state were calculated. A summary of the results at T = 298.15 K (p = 0.1 MPa)is shown in Table 1. Using these results and those previously obtained for the free ligand, 5,10,15,20-tetrakis(4-methoxyphenyl)porphine, the mean dissociation enthalpy for the Zn-N coordination bond is obtained as D(Zn-N)= (160 ± 9) kJ·mol-1. This value is consistent with the results obtained using the same experimental approachin a similar system (5,10,15,20-tetraphenylporphine, TPP/ZnTPP) reported elsewhere. A discussion of the strengthfor the Zn-N coordination bond is made in terms of the structural and electronic features of the molecules involved.