Charge Transfer or J-Coupling? Assignment of an Unexpected Red-Shifted Absorption Band in a Naphthalenediimide-Based Metal鈥揙rganic Framework

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• 作者：Brian D. McCarthy ; Eric R. Hontz ; Shane R. Yost ; Troy Van Voorhis ; Mircea Dinc膬
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2013
• 出版时间：February 7, 2013
• 年：2013
• 卷：4
• 期：3
• 页码：453-458
• 全文大小：300K
• 年卷期：v.4,no.3(February 7, 2013)
• ISSN：1948-7185

文摘

We investigate and assign a previously reported unexpected transition in the metal鈥搊rganic framework Zn₂(NDC)₂(DPNI) (1; NDC = 2,6-naphthalenedicarboxylate, DPNI = dipyridyl-naphthalenediimide) that displays linear arrangements of naphthalenediimide ligands. Given the longitudinal transition dipole moment of the DPNI ligands, J-coupling seemed possible. Photophysical measurements revealed a broad, new transition in 1 between 400 and 500 nm. Comparison of the MOF absorption spectra with that of a charge transfer (CT) complex formed by manual grinding of DPNI and H₂NDC led to the assignment of the new band in 1 as arising from an interligand CT. Constrained density functional theory utilizing a custom long-range-corrected hybrid functional was employed to determine which ligands were involved in the CT transition. On the basis of relative oscillator strengths, the interligand CT was assigned as principally arising from 蟺-stacked DPNI/NDC dimers rather than the alternative orthogonal pairs within the MOF.

Keywords:

charge transfer; constrained DFT; Koopman鈥檚 theorem; J-coupling; metal鈭抩rganic frameworks