When comparing the emission bands of 7bx and 7cx to the mono-substituted quinoline (9b) and the di-substituted quinoline (9c) (Figure ) respectively in solution, we see that the emission in each case of is coming from the aromatic quinoline. 7cx emission bands match the more vibronic character of the di-substituted quinoline emission bands. When dissolved in 0.1 M H2SO4 the emission of 7cx at approximately 3 eV matches the energy of 9c emission. This is also the case for 7bx where the energies of both the doubly protonated and unprotonated compounds match the mono-substituted quinoline (9b), showing that the caged unit of all the compounds is only applicable when looking at the charge transfer behaviour of the molecule. Thus, tuning the position of the cage attachment and the number of the methoxy units on the quinoline affords great control over the strength of the CT state. Interestingly, varying the functionality α-to nitrogen (i.e. ketone, amide or tert-butyl) has very limited impact on the photophysical properties. This therefore enables variation of the pKa of the tertiary amine moiety while retaining essentially identical photophysical properties, suggesting such compounds may have useful function as pH sensors. A subsequent investigation into the position of the quinoline moiety in relation to the nitrogen atom within the caged species was performed to explore the effect of N-aryl distance on TSCT state formation. As mentioned previously, the quinoline moiety of the compound was shifted one place closer to the caged nitrogen atom in 7dx, compared to 7ax, to see whether this influenced the photophysical characterisation. 7aa and 7da were studied (Figure ) in five different solvents with increasing polarity to observe solvatochromism effects. The absorption and excitation profiles in these different solvents can be found in Figures and. Figure shows the emission of 7aa which has the quinoline at position 4 of the ring. We see little change in the emission peak on increasing the polarity of the solvents and there is only a slight red shift in the peak on dissolving the compound in acetonitrile. 7aa shows a more vibronic character in contrast to the 7da emission profile in Figure , which has a broader emission spectrum characteristic of CT states and a strong bathochromic shift with increasing polarity. 7da in methylcyclohexane has an emission peak of 3.1 eV which undergoes a 0.7 eV shift to 2.4 eV when dissolved in acetonitrile. This shift in emission can be rationalised through the position of the lone pair of the nitrogen being closer to the quinoline moiety and so giving clear indication of a TSCT between the two components. The switching on and off of TSCT through change in position by a single carbon bond shows the sensitivity of the formation of these states.