The Pyreno‐Triazinyl Radical – Magnetic and Sensor Properties

We report the first example of a stable pyrenotriazinyl radical, 1,3‐diphenyl‐1,2,4‐pyrenotriazin‐4‐yl ( PyT ). Magnetic susceptibility measurements of the radical PyT show a transition from a paramagnetic state to an antiferromagnetic state. The pyrene moiety has a strong influence via ππ interactions in 1D chain stacks that result in the observed magnetic properties. Unexpectedly, the pyrene unit has essentially no effect on the electronic structure of the triazinyl core. Chemical sensing studies on various nitrophenol‐based compounds showed that the radical PyT exclusively senses picric acid ( PA ), as a pH sensor, with a detection limit of 5.0×10 −6 M.