**Author details**

446 Advanced Aspects of Spectroscopy

**Figure 23.** Chemical structures of Un-LTAM , with *ZEE* and *ZEZ* configurations.

LTAM dyes is expected to have an *E* configuration.

molecules examined previously.

respectively.

**5. Conclusion** 

The double bonds C2=C7'', C8''=C9'', and C2'=C11'' of Un-LTAM **4** have *EEE* configurations. The *EEE* isomers of these LTAM dyes are formed as the sole product in all cases, even though there are three possible isomers, the two other diastereomers being the *ZEE* and *ZEZ* isomers, as shown in Fig. 23. Generally, the central carbon-carbon double bond of these

Although the presence of the *ZEE* and *ZEZ* diastereomers was generally expected to be found in organic solvents, none of these isomers were detected, unlike for the LTAM

Fig. 24 shows the molecular packing diagram of Un-LTAM **4**, showing the formation of the dimer, which is stacked in an alternating fashion in the unit cell of the crystal. The intermolecular distances in the dimer are 8.53 and 9.40 Å, for the FB and phenyl rings,

**Figure 24.** Molecular packing diagram of Un-LTAM **4**, showing formation of the dimer.

Novel Fischer's base analogs of LTAM and Un-LTAM molecules and their corresponding TAM+ dyes have been successfully developed. 1H and 13C NMR assignments for the prepared LTAM molecules have been completed by 1D and 2D NMR experiments, including DEPT, COSY, HSQC, HMBC, and NOESY. The geometry of the double bond was Z*E* in most cases, as measured directly by NOESY. The *EE* and *ZZ* isomers have *C*<sup>2</sup> symmetry, and hence, the two FB rings of these isomers are identical. Therefore, the 1H NMR spectra of the *EE* and *ZZ* isomers are expected to be relatively simple compared to those of the *ZE* isomer. The novel LTAM molecules exist as a single isomer (*ZE* or *EE*) in the Sam-Rok Keum, So-Young Ma and Se-Jung Roh *Korea University at Sejong Campus, South Korea* 
