Who was the titan of the sun

I think it's Helios.

Helios in Mythology. In Greek mythology, Helios is the offspring of the titans Hyperion and Theia. His sisters were Selene (the Moon) and Eos (Dawn). Hesiod informs us in his Theogony that with Perseis, daughter of Ocean, he had two children, Circe and king Aietes, who ruled at Kolchis.