the present invention provides , in part , compounds of formula i : and pharmaceutically acceptable salts thereof ; processes for the preparation of ; intermediates used in the preparation of ; and compositions containing such compounds or salts , and their uses for treating d1 - mediated disorders including , e . g ., schizophrenia , cognitive impairment , adhd , impulsivity , compulsive gambling , overeating , autism spectrum disorder , mci , age - related cognitive decline , dementia , rls , parkinson &# 39 ; s disease , huntington &# 39 ; s chorea , anxiety , depression , mdd , trd , bipolar disorder , chronic apathy , anhedonia , chronic fatigue , post - traumatic stress disorder , seasonal affective disorder , social anxiety disorder , post - partum depression , serotonin syndrome , substance abuse and drug dependence , drug abuse relapse , tourette &# 39 ; s syndrome , tardive dyskinesia , drowsiness , excessive daytime sleepiness , cachexia , inattention , sexual dysfunction , migraine , sle , hyperglycemia , atherosclerosis , dislipidemia , obesity , diabetes , sepsis , post - ischemic tubular necrosis , renal failure , hyponatremia , resistant edema , narcolepsy , hypertension , congestive heart failure , postoperative ocular hypotonia , sleep disorders , and pain .