Crystal structure determination as part of an undergraduate laboratory experiment: 1′,3′,3′-trimethylspiro[chromene-2,2′-indoline] and 1′,3′,3′-trimethyl-4-[(E)-(1,3,3-trimethylindolin-2-ylidene)methyl]spiro[chroman-2,2′-indoline]

The crystal structures of the title compounds, C19H19NO and C31H34N2O, were determined as part of an experiment in an undergraduate teaching laboratory that demonstrates the relationship between molecular structure and function. 1′,3′,3′-Trimethylspiro[chromene-2,2′-indoline] is both a photoswitch and thermochromic molecule. Students synthesized it and a bis-indoline adduct and compared the crystallographically determined structures to computed gas-phase models.