Is Lexapro a benzodiazepine

No.

Buspirone (brand name Buspar) is a psychoactive drug and pharmaceutical medication of the piperazine and azapirone chemical classes. It is used primarily as an anxiolytic, specifically for generalized anxiety disorder. Bristol-Myers Squibb (BMS) gained Food and Drug Administration (FDA) approval for buspirone in 1986 for generalized anxiety disorder only, and it became available as a generic in 2001.

Source:wikipedia