Condensed phase transferred hydrocarbon chains

In Figure 7 a comparison is made of the frequency of the CHj antisymmetric stretching vibration as a function of molecular area for DPPC monolayer films at the A/W and A/Ge interfaces. As described above, the frequency of (his vibration is related to the overall macromolecular conformation of the lipid hydrocarbon chains. For the condensed phase monolayer (-40-45 A2 molecule 1), the measured frequency of the transferred monolayer film is virtually the same as that of the in-situ monolayer at the same molecular area, indicating a highly ordered acyl chain, predominately all-trans in character. For LE films as well as films transferred in the LE-LC phase transition region, however, the measured frequency appears independent (within experimental uncertainty) of the surface pressure, or molecular area, at which the film was transferred. The hydrocarbon chains of these films are more disordered than those of the condensed phase transferred films. However, no such easy comparison can be made to the in-situ monolayers at comparable molecular areas. For the LE monolayers (> ca. 70 A2 molecule 1), the transferred monolayers are more ordered than the in-situ film. In the LE-LC phase transition region ( 55-70 A2 molecule 1), the opposite behavior occurs. 

The results for the calculation of the orientation distribution for the hydrocarbon chains in the transferred monolayer films are presented in Figure 8. As is the case with the orientation distribution of the in-situ monolayers, the transferred films have a similar tilt angle in the expanded and phase transition regions. For the transferred monolayer, however, the tilt angle is in the range 35-40° from the surface normal, a much more oriented monolayer than the calculations indicate for the in-situ film (Figure 5). Figure 8 also shows that the condensed phase transferred monolayers are more oriented than those films transferred in the LE and LE-LC... 

In the bridged EDA molecule I (Figure 7) where the donor dimethylaniline and the acceptor anthracene are bridged by a saturated hydrocarbon chain -(CH2),-, the features of the electron-transfer reaction are known to be strongly dependent on the chain length n. Mataga and co-workers demonstrated that in the condensed phase bridged EDA molecules with = 0, 1 and 2 formed the CT state only in polar solvents. In the case of = 3, the CT state was formed even in non-polar solvents [86]. The rise time of the CT emission in 2-propanol was 54 and 93 ps for n = 1 and 2, respectively. In -hexane solvent, a rise time of 2.6 ns was reported for the = 3 molecule. 

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