Disclosed herein are clusters compounds that include at least one substituted amine sulfate and at least one substituted amine bisulfate molecule. The substituted amine sulfate molecule and the substituted amine bisulfate molecule may each include an ammonium moiety with at least one alkyl substituent. Optionally, the alkyl substituent can include 1 to 20 carbon atoms, 1 to 10 carbon atoms, or 1 to 6 carbon atoms. For example, the alkyl substituent can be a methyl, ethyl, propyl, butyl, or pentyl group. In some examples, the substituted amine sulfate molecule and the substituted amine bisulfate molecule each include an ammonium moiety with at least two alkyl substituents. Optionally, the two alkyl substituents are the same. Alternatively, however, the two alkyl substituents can be different.