Generation and characterization of high-spin organic molecules

5 Generation and characterization of high-spin organic molecules 

Encouraged by the experimental finding (Itoh, 1967 Wasserman et al., 1967) that the dicarbene [15 m — 2] ( = [3]) had a ground quintet state, i.e. all four spins were ferromagnetically coupled, Iwamura and Itoh have been engaged in a project directed towards the construction of the higher series of poly(carbenes) [15], [23] and [24] (Iwamura et al., 1985 Teki et al., 1983, 1985, 1986). 

The spin distribution in the lower homologue [15 m — 2] was most elegantly studied by Takui et al. (1989) by means of a combination of ENDOR experiments and theoretical calculations within the framework of a generalized UHF Hubbard model (Teki et al., 1987a) and a Heisenberg model (Teki et al., 1987b). The spin distribution obtained is just as expected qualitatively in Fig. 7. 

Tetracarbene [24 m = 4] has been generated in a 2-methyltetrahydro-furan (2-MTHF) matrix and analysed based on (9) to give preliminary data g = 2.0030, D = 0.01400 and E = 0.00050cm-1 with 5 = 4. Note that the. E-value of the last compound is almost vanishing due to the cylindrical symmetry of the molecule. 

Epr signals due to the triplet and quintet states were obtained when single crystals of diacetylene were photolysed (Huber and Schwoerer, 1980 Schwoerer et al., 1981 Sixl et al., 1986). The quintet states are considered to arise from substructures such as [25]. 

---

Generation and characterization of high-spin organic molecules 210 Cross-conjugated poly(carbenes) 210 Other high-spin molecules 215... 

---