Homoleptic, Four-Coordinate Azadipyrromethene Complexes of d10 Zinc and Mercury

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• 作者：Thomas S. Teets ; David V. Partyka ; James B. Updegraff III ; Thomas G. Gray
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：April 7, 2008
• 年：2008
• 卷：47
• 期：7
• 页码：2338 - 2346
• 全文大小：2427K
• 年卷期：v.47,no.7(April 7, 2008)
• ISSN：1520-510X

文摘

Tetraarylazadipyrromethenes, and especially their boron chelates, are a growing class of chromophores that are photoactive toward red light. The coordination chemistry of these ligands remains to be explored. Reported here are four-coordinate zinc(II) and mercury(II) complexes of tetraarylazadipyrromethene ligands. The new complexes contain two azadipyrromethenes bound per d¹⁰ metal center and are characterized by ¹H NMR, optical absorption spectroscopy, X-ray diffraction crystallography, and elemental analysis. Solid-state structures show that these bis-chelate complexes distort significantly from idealized D_2d symmetry. AM1 geometry optimizations indicate relaxation energies in the range of 6.8–15.2 kcal mol⁻¹; interligand π-stacking provides an added energetic impetus for distortion. The absorption spectra show a marked increase in the absorption intensity in the red region and, in the case of the zinc(II) complexes, the development of a second distinct absorption band in this region, which is red-shifted by ca. 40–50 nm relative to the free ligand. Semiempirical INDO/S computations indicate that these low-energy optical absorptions derive from allowed excitations among ligand-based orbitals that derive from the highest occupied molecular orbital and lowest unoccupied molecular orbital of the free azadipyrromethene.