Recent changes to
biblatex (in v1.6) mean that the
biblatex-chem bundle is currently broken. I’ve not released a quick-fix as there are some long-standing issues to address in biblatex-chem. When I initially wrote the code, I started from scratch and defined only what I wanted. That works, but means that any changes in
biblatex are not automatically picked up. From
biblatex-ieee, I took the alternative approach and worked from the standard
biblatex styles to what was needed. That’s a better long-term approach, so it’s the one I’m now bringing to biblatex-chem. It will take a little while, so user might want to keep an eye on the development code.