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In this combined experimental and theoretical study, a computational protocol is reported to predict the excited states in D‐π‐A compounds containing the B(FXyl)2 (FXyl = 2,6‐bis(trifluoromethyl)phenyl) acceptor group for the design of new thermally activated delayed fluorescence (TADF) emitters. To this end, the effect of different donor and π‐bridge moieties on the energy gaps between local and charge‐transfer singlet and triplet states is examined. To prove this computationally aided design concept, the D‐π‐B(FXyl)2 compounds 1–5 were synthesized and fully characterized. The photophysical properties of these compounds in various solvents, polymeric film, and in a frozen matrix were investigated in detail and show excellent agreement with the computationally obtained data. Furthermore, a simple structure–property relationship is presented on the basis of the molecular fragment orbitals of the donor and the π‐bridge, which minimize the relevant singlet–triplet gaps to achieve efficient TADF emitters. [ABSTRACT FROM AUTHOR]

It is shown, quantum chemically, how structural distortion of an aromatic dye molecule can be leveraged to rationally tune its optoelectronic properties. By using a quantitative Kohn–Sham molecular orbital (KS‐MO) approach, in combination with time‐dependent DFT (TD‐DFT), the influence of various structural and electronic tuning parameters on the HOMO–LUMO gap of a benzenoid model dye have been investigated. These parameters include 1) out‐of‐plane bending of the aromatic core, 2) bending of the bridge with respect to the core, 3) the nature of the bridge itself, and 4) π–π stacking. The study reveals the coupling of multiple structural distortions as a function of bridge length and number of bridges in benzene to be chiefly responsible for a decreased HOMO–LUMO gap, and consequently, red‐shifting of the absorption wavelength associated with the lowest singlet excitation (λ≈560 nm) in the model cyclophane systems. These physical insights together with a rational approach for tuning the oscillator strength were leveraged for the proof‐of‐concept design of an intense near‐infrared (NIR) absorbing cyclophane dye at λ=785 nm. This design may contribute to a new class of distortion‐controlled NIR absorbing organic dye molecules. [ABSTRACT FROM AUTHOR]

The unusually fast Diels–Alder reactions of [5]cyclophanes were analyzed by DFT at the BLYP‐D3(BJ)/TZ2P level of theory. The computations were guided by an integrated activation‐strain and Kohn–Sham molecular orbital analysis. It is revealed why both [5]metacyclophane and [5]paracyclophane exhibit a significant rate enhancement compared to their planar benzene analogue. The activation strain analyses revealed that the enhanced reactivity originates from 1) predistortion of the aromatic core resulting in a reduced activation strain of the aromatic diene, and/or 2) enhanced interaction with the dienophile through a distortion‐controlled lowering of the HOMO–LUMO gap within the diene. Both of these physical mechanisms and thus the rate of Diels–Alder cycloaddition can be tuned through different modes of geometrical distortion (meta versus para bridging) and by heteroatom substitution in the aromatic ring. Judicious choice of the bridge and heteroatom in the aromatic core enables effective tuning of the aromatic Diels–Alder reactivity to achieve activation barriers as low as 2 kcal mol−1, which is an impressive 35 kcal mol−1 lower than that of benzene. [ABSTRACT FROM AUTHOR]

Principles are presented for the design of functional near‐infrared (NIR) organic dye molecules composed of simple donor (D), spacer (π), and acceptor (A) building blocks in a D‐π‐A fashion. Quantitative Kohn–Sham molecular orbital analysis enables accurate fine‐tuning of the electronic properties of the π‐conjugated aromatic cores by effecting their size, including silaaromatics, adding donor and acceptor substituents, and manipulating the D‐π‐A torsional angle. The trends in HOMO–LUMO gaps of the model dyes correlate with the excitation energies computed with time‐dependent density functional theory at CAMY‐B3LYP. Design principles could be developed from these analyses, which led to a proof‐of‐concept linear D‐π‐A with a strong excited‐state intramolecular charge transfer and a NIR absorption at 879 nm. © 2018 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc. Capturing the Lost Photons: near‐infrared (NIR)‐absorbing D‐π‐A organic dyes are rare and often discovered via laborious exploration and serendipity. Herein, based on quantitative Kohn–Sham MO and time‐dependent density functional theory analyses, the authors develop a toolbox of generic design principles that support a more rational and efficient approach toward such dyes. The authors provide a proof of principle for their approach by in‐silico rational design of a NIR‐absorbing dye molecule. [ABSTRACT FROM AUTHOR]