文摘
Structural information on the solid forms of efavirenz, a non-nucleoside reverse transcriptase inhibitor, is limited, although various polymorphic forms of this drug have been patented. We report here structural studies of four new crystal forms—a pure form, a cyclohexane solvate, and cocrystals with 1,4-cyclohexanedione and 4,4′-bipyridine. Temperature dependent single-crystal to single-crystal phase transitions are observed for the pure form and for the cyclohexane solvate with an increase in the number of symmetry independent molecules, Z′, upon a lowering of temperature. Other issues related to these solid forms, such as thermal stability, conformational flexibility, and high Z′ occurrences, are addressed by using a combined experimental and computational approach.