A compound having the formula I: or a pharmaceutically acceptable salt thereof, wherein R 1 is hydrogen; R 2, R 3, R 4, R 5, R 8, and R 9 are independently hydrogen or -C 1-6 alkyl; R 6 is hydrogen, -OH, -C 1-6 alkyl, -OC 1-6 alkyl, aryl, or halogen, or together with R 7, forms an oxo group, or together with R 7 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms, wherein alkyl and aryl are unsubstituted or independently mono-, di-, or tri-substituted with R 14; R 7 is hydrogen, C 1-6 alkyl,-CF 3, aryl, -O-aryl, -O-C 1-6 alkyl, -C(R 15 R 16)OH, a 5-7-membered heteroaryl having 1, 2, 3 or 4 nitrogen atoms, or halogen, or together with R 6, forms an oxo group, or together with R 6 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms wherein alkyl, aryl and heteroaryl are unsubstituted or independently mono-, di- or tri-substituted with R 14; R 10 and R 11 are independently hydrogen, -C 1-6 alkyl, -OH, -OC 1-6 alkyl, or halogen; R 12 is hydrogen, C 1-6 alkyl, or -(CH 2) 1-2 OH, or together with R 13 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or -C 1-6 alkyl; R 13 is -C 1-6 alkyl or -(CH 2) 1-2 OH, or together with R 12 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or -C 1-6 alkyl; R 14, each time in which it occurs, is independently halogen, hydroxyl, -C 1-6 alkyl, -CF 3, aryl or trimethylsilyl; and R 15 and R 16 are independently hydrogen or C 1-6 alkyl; and pharmaceutically acceptable salts thereof; wherein the following compounds are excluded: O 2 -[4-(hydroxymethyl)cyclohexyl] 1-( N,N,-diethylamino)diazen-1-ium-1,2-diolate; O 2 -[4-(hydroxymethyl)cyclohexyl] 1-( N - tert -butylmethylamino)diazen-1-ium-1,2-diolate; and 1-((2-hydroxycyclohexyl)oxy)-2-oxo-3,3-diethyl-1-triazene. R 1 is hydrogen; R 2, R 3, R 4, R 5, R 8, and R 9 are independently hydrogen or -C 1-6 alkyl; R 6 is hydrogen, -OH, -C 1-6 alkyl, -OC 1-6 alkyl, aryl, or halogen, or together with R 7, forms an oxo group, or together with R 7 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms, wherein alkyl and aryl are unsubstituted or independently mono-, di-, or tri-substituted with R 14; or together with R 7, forms an oxo group, or together with R 7 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms, R 7 is hydrogen, C 1-6 alkyl,-CF 3, aryl, -O-aryl, -O-C 1-6 alkyl, -C(R 15 R 16)OH, a 5-7-membered heteroaryl having 1, 2, 3 or 4 nitrogen atoms, or halogen, or together with R 6, forms an oxo group, or together with R 6 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms wherein alkyl, aryl and heteroaryl are unsubstituted or independently mono-, di- or tri-substituted with R 14; or together with R 6, forms an oxo group, or together with R 6 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms R 10 and R 11 are independently hydrogen, -C 1-6 alkyl, -OH, -OC 1-6 alkyl, or halogen; R 12 is hydrogen, C 1-6 alkyl, or -(CH 2) 1-2 OH, or together with R 13 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or -C 1-6 alkyl; or together with R 13 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or -C 1-6 alkyl; R 13 is -C 1-6 alkyl or -(CH 2) 1-2 OH, or together with R 12 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or -C 1-6 alkyl; or together with R 12 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or -C 1-6 alkyl; R 14, each time in which it occurs, is independently halogen, hydroxyl, -C 1-6 alkyl, -CF 3, aryl or trimethylsilyl; and R 15 and R 16 are independently hydrogen or C 1-6 alkyl; and pharmaceutically acceptable salts thereof; wherein the following compounds are excluded: O 2 -[4-(hydroxymethyl)cyclohexyl] 1-( N,N,-diethylamino)diazen-1-ium-1,2-diolate; O 2 -[4-(hydroxymethyl)cyclohexyl] 1-( N - tert -butylmethylamino)diazen-1-ium-1,2-diolate; and 1-((2-hydroxycyclohexyl)oxy)-2-oxo-3,3-diethyl-1-triazene. O 2 -[4-(hydroxymethyl)cyclohexyl] 1-( N,N,-diethylamino)diazen-1-ium-1,2-diolate; O 2 -[4-(hydroxymethyl)cyclohexyl] 1-( N - tert -butylmethylamino)diazen-1-ium-1,2-diolate; and 1-((2-hydroxycyclohexyl)oxy)-2-oxo-3,3-diethyl-1-triazene.