Push-pull chromophores with low singlet-triplet gaps

Had I known how much work it would be, I might have said no when a colleague from organic synthesis asked me to do some calculations for him. But then, the difficult projects are usually also the interesting ones. The question we wanted to answer is why a set of isomeric molecules, that looked very similar on paper, had completely different emission properties and solvatochromic shifts.

First it took quite a while to find an appropriate density functional that could properly reproduce the data. And once I had one, I noticed that the solvatochromic shifts were completely off. That's when I realized that I had to ask someone who actually knows something about solvation. This is where my colleague Jan came into play. He made the smart move of abandoning TDDFT and doing things at the ab initio ADC level. For this purpose, he used a solvation model that he had just implemented. And suddenly everything worked out brilliantly.

For more information, you can find our new paper "Charge transfer states in triazole linked donor-acceptor materials: strong effects of chemical modification and solvation" that just appeared in PCCP.