Electronic states of alkali metal-NTCDA complexes: A DFT study

• DFT calculations were carried out for Alkali metal-NTCDA system
• Effects of Alkali metals on the band gap of NTCDA were examined.
• It was found that the band gap is red-shifted.
• Mechanism of specific band gap feature was discussed.

Structures and electronic states of organic–inorganic compound of 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA) with alkali metals, Mn(NTCDA) (MLi and Na, n = 0–2), have been investigated by means of hybrid density functional theory (DFT) calculations. From the DFT calculations, it was found that the electronic state of the complex at the ground state is characterized by a charge-transfer state expressed by (M)+(NTCDA)−. The alkali metals were bound equivalently to the carbonyl oxygen and ether oxygen atoms of NTCDA. The CO double bond character of NTCDA was changed to a C–O single bond like character by the strong interaction of M to the CO and O sites. This change was the origin of the red-shift of the IR spectrum. The UV–vis absorption spectra of Mn(NTCDA) were theoretically predicted on the basis of theoretical results.

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