第 109 回フロンティア材料研究所講演会
7 月 29 日（月）14 時～

R3 棟 1 階会議室にてTransition Elements inspired Inorganic Pigments:
The Importance of Coordination Geometry
Srinivasan Natarajan*Framework Solids Laboratory, Solid State and Structural Chemistry Unit, Indian Institute of Science,
Bangalore 560 012, India.
* snatarajan@iisc.ac.in

Crystalline inorganic oxides displaying bright colours attracted much attention from early days forapplication as gemstones and pigments. Ruby (Cr3+ doped Al2O3) and Emerald (Cr3+ doped
Be3Al2(SiO3)6) and Azurite (Cu3(CO3)2(OH)2), Han blue (BaCuSi2O6) and Turquoise(CuAl6(PO4)4(OH)8·4H2O) for example found application as gemstones and pigments since ancienttimes.[1] In addition to the naturally occurring gemstones and pigments, several man-made (synthetic)
coloured solids were also developed to meet the demand.[1] Y2BaCuO5, copper substituted apatites,Mn(III) substituted YInO3 and CaTaO2N – LaTaON2 pervoskites are some of the more recent pigment
materials for green, blue, red-yellow colours.[2,3] A scientific inquiry into the origin of colours ofinorganic solids is essential for a rational design and synthesis of coloured materials. While there areseveral causes for the colour of solids, the main factor that causes colour in an inorganic oxide
containing transition metal ion is the electronic transitions within the partially filled d-states arisingfrom the ligand field effects around the transition metal ion. Octahedral and tetrahedral are the mostcommon geometries where the colour and optical absorption spectra of all the transition metal ions havebeen well-documented. Transition metal ions in less symmetric geometries such as distorted octahedral
and five-fold coordinated (square pyramidal and trigonal bipyramidal) geometries produce colours
different from those in regular octahedral and tetrahedral geometries in materials. The present talkwould address some of these issues and our efforts towards identifying new chromophores employing
transition metal chemistry.[4-6]

Li2MnO3

YGa1-xMnxO3 Ca3Sb2GaFeCoO12[1] P. Ball, Bright Earth: Art and the Invention of Color, The University of Chicago Press, Chicago, 2001.
[2] P.E. Kazin, M.A. Zykin,Y.V. Zubavichus, O.V. Magdysyuk, R.E. Dinnebier, and M. Jansen, Chem. –European J., 2014,20,165; M. Jansen, H. P. Letschert, Nature, 2000, 404, 980.
[3] A. E. Smith, H. Mizoguchi, K. Delaney, N. A. Spaldin, A. W. Sleight, M. A. Subramanian, J. Am. Chem. Soc., 2009, 131,17084.
[4] S. Tamilarasan, D. Sarma, S. Natarajan and J. Gopalakrishnan, Inorg. Chem., 2013, 52, 5757; S. Tamilarasan, D. Sarma,
M.L.P. Reddy, S. Natarajan, J. Gopalakrishnan, RSC Advances, 2013, 3, 3199; S Tamilarasan, S Laha, S Natarajan, J
Gopalakrishnan, J. Mater. Chem. C, 2015, 3, 4794; S. Tamilarasan, S. Laha, S. Natarajan and J. Gopalakrishnan, Eur. J. Inorg.
Chem., 2016, 288; S. Tamilarasan, S. Natarajan and J. Gopalakrishnan, Chemistry – An Asian J. (2016), 11, 3234.
[5] S. Laha, S. Tamilarasan, S. Natarajan and J. Gopalakrishnan, Inorg. Chem., 2016, 55, 3508; S. Laha, S. Natarajan and J.
Gopalakrishnan, Eur. J. Inorg. Chem., 2016, 288 – 293.
[6] A. Bhim, S. Laha, J. Gopalakrishnan and S. Natarajan, Chemistry – An Asian J, 2017, 12, 2734 – 2743; Eur. J. Inorg.
Chem., 2018, 2277, Inorg. Chem., (2019) in press.

連絡先：東・山本 研究室（5315）