| A series of cymantrene derivatives, CME, CMC, S2, S3, A1, A2, A3, and A4 ((eta5-C5H 4R)Mn(CO)3, R = COOCH3, CH2Cl, COCH(SCH 3)2, COC(SCH3)3, CH2COPy, CH2CHCNPy, CH2CH(CSNH2)Py, C(OH)CCNPy, respectively, where Py = 2-pyridyl) have been synthesized and characterized spectroscopically. UV photolysis of S2, S3, A1, A2, and A3 results in the formation of red chelates, rS2, rS3, rA1N, rA2N, and rA3S ((eta1:eta5-C5H 4R)Mn(CO)2, R = COCH(SCH3)2, COC(SCH 3)3, CH2COPy (Py bound), CH2CHCNPy (Py bound), CH2CH(CSNH2)Py (S bound), respectively). Both S2 and S3 exhibit efficient chelation with unit quantum yields. From TRIR experiments, UV photolysis of S2 in n-heptane yields a mixture of rS2 and solvated complex. The solvate converts to rS2 within 200 ns. Whereas, photolysis of S3 yields rS3 exclusively within 40 ps. From FTIR experiments, when the photolysis of S2, S3, rS2, or rS3 is performed in acetonitrile solvent, no solvation is observed for S2 or S3, and ring opening is observed for rS2 but not rS3. Two of the chelates are photochromic. Correlated by 1H-NMR, UV-vis, and IR spectroscopies, a deep purple rA1N changes to deep blue rA1O during one min of visible photolysis. The deep blue rA1O returns to rA1N upon standing at room temperature for 5 min. |
