Imidazolidine and 1, 4-diazepane analogs of N-(2-benzofuranyl) methyl-N′-(4- alkoxybenzyl) piperazines were prepared to explore the effect of ring contraction and expansion on σ receptor affinity and subtype selectivity within a series of cyclic diamines. In vitro receptor binding assays revealed that all cyclic vicinal diamines possessed affinity and selectivity for σ1 receptors. The imidazolidines possessed nanomolar σ1 affinities (Ki= ...