10.1021/jz302076s.s001 Brian D. McCarthy Brian D. McCarthy Eric R. Hontz Eric R. Hontz Shane R. Yost Shane R. Yost Troy Van Voorhis Troy Van Voorhis Mircea Dincă Mircea Dincă Charge Transfer or J‑Coupling? Assignment of an Unexpected Red-Shifted Absorption Band in a Naphthalenediimide-Based Metal–Organic Framework American Chemical Society 2015 DPNI interligand CT charge MOF absorption spectra 2NDC NDC alternative orthogonal pairs transition 2015-12-16 22:23:17 Journal contribution https://acs.figshare.com/articles/journal_contribution/Charge_Transfer_or_J_Coupling_Assignment_of_an_Unexpected_Red_Shifted_Absorption_Band_in_a_Naphthalenediimide_Based_Metal_Organic_Framework/2022282 We investigate and assign a previously reported unexpected transition in the metal–organic framework Zn<sub>2</sub>(NDC)<sub>2</sub>(DPNI) (<b>1</b>; 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 <b>1</b> 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 H<sub>2</sub>NDC led to the assignment of the new band in <b>1</b> 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 π-stacked DPNI/NDC dimers rather than the alternative orthogonal pairs within the MOF.