The invention provides compounds of Formula (I): wherein R1-R4, p and q have any of the values described in the specification, as well as pharmaceutical salts thereof, and pharmaceutical compositions containing such compounds or salts. The compounds and salts are 5-HT ligands and are useful for treating diseases, disorders, and/or conditions in a mammal wherein activity of a 5-HT receptor is implicated. The compounds and salts are particularly useful for treating diseases of the central nervous system.