I'm thinking about designing an alien race. The race is carbon-based and evolved on a world with an average surface temperature between 40 and 60 degrees Celsius. Now, on Earth, almost all lifeforms use some form of nucleoside triphosphate, such as ATP or GTP, for energy exchange. What are possible alternative energy carriers besides nucleoside triphosphates? Bonus points if the energy carrier isn't phosphate-based, although that isn't a requirement.
A great many high energy molecules exist, countless millions in fact. So part of your question is fairly easy to answer starting with the more obvious, how about using a different nucleoside base to attach a phosphate group such as these:
If you don’t like phosphates how about adenosine nitrate?
If you don’t like nucleosides why not go the whole hog and abandon terrestrial biology entirely? No doubt with suitably ingenious alien biochemistry it would be possible to utilize Tetrazine or a million other high energy molecules.
The scope of chemistry is vast beyond imagination. Determining all of the relevant chemical reactions required to support your alternative high energy molecule is another matter.
It would basically mean creating an alternative to this map of reactions (and this is just a fragment)