Experimental and Computational Investigation of the Photophysical Properties of a Series of Luminescent D−A−D’ and D−A−A’ Pyrimidines

Pyrimidines, a prominent isomer class of diazines, are promising molecular constituents of electron‐deficient luminescent and hole‐transport materials. Here, we report the fluorescence lifetimes and describe the electronic structures and character of low‐lying emissive excited states of a series of synthetically accessible donor‐acceptor‐donor (D−A−D′) and donor‐acceptor‐acceptor (D−A−A′) type pyrimidines, including both all‐organic and hybrid organic‐organometallic analogues. We find that strategically varying the aryl substituents on a pyrimidine enables tuning of the character of the luminescent excited states from charge‐transfer (CT) to locally excited (LE) states, which then differ in their sensitivity to their environment. This study suggests structural handles for controlling the photophysics of arylpyrimidines relevant to a variety of applications for luminescent materials.