This article describes the design rationale for highly electron-rich dipyrrolonaphthyridinedione (DPND) derivatives bearing substituted amino groups at the 3 and 9 positions, which exhibit absorption in the red and emission in the red/NIR region of the spectrum. These novel dyes are easily synthesized through a two-step protocol consisting of bromination of the DPND molecule followed by Buchwald-Hartwig amination. We demonstrated that the diamino-dipyrrolonaphthyridinediones have high ionization energies (∼4.7 eV) and that the spectroelectrochemical properties can be rationally tuned by altering the nature of the peripheral substituted amino groups. All amino-DPNDs exhibit solvatofluorochromism, which has not been previously reported for dyes possessing this core. Theoretical calculations reveal that in all cases, the strongest absorption is exhibited by the S states which clearly correlate with the HOMO-LUMO orbital transition. As all higher states have lower oscillator strengths, it is clear that fluorescence is completely dominated by the excitation/deexcitation sequence S → S, S → S and that there are no contributions to the fluorescence from excitations to higher states.

A reformulation of the combined density functional theory and multireference configuration interaction method (DFT/MRCI) is presented. Expressions for ab initio matrix elements are used to derive correction terms for a new effective Hamiltonian. On the example of diatomic carbon, the correction terms are derived, focusing on the doubly excited 1 Δ g state, which was problematic in previous formulations of the method, as were double excitations in general. The derivation shows that a splitting of the parameters for intra-and interorbital interactions is necessary for a concise description of the underlying physics. Results for 1 L a and 1 L b states in polyacenes and 1 A u and 1 A g states in mini-β-carotenoids suggest that the presented formulation is superior to former effective Hamiltonians. Furthermore, statistical analysis reveals that all the benefits of the previous DFT/MRCI Hamiltonians are retained. Consequently, the here presented formulation should be considered as the new standard for DFT/MRCI calculations.