In one aspect, the invention relates to substituted 2-(4-heterocyclylbenzyl)isoindolin-1-one analogs compounds, derivatives thereof, and related compounds which are useful as positive allosteric modulators of the muscarinic acetylcholine receptor M 1 (mAChR M 1 ); synthesis methods for making the compounds; pharmaceutical compositions comprising the compounds; and methods of treating neurological and psychiatric disorders associated with muscarinic acetylcholine receptor dysfunction using the compounds and compositions.