Soft chromophore featured liquid porphyrins and their utilization toward liquid electret applications

Optoelectronically active viscous liquids are ideal for fabricating foldable/stretchable electronics owing to their excellent deformability and predictable π-unit–based optoelectronic functions, which are independent of the device shape and geometry. Here we show, unprecedented ‘liquid electret’ devices that exhibit mechanoelectrical and electroacoustic functions, as well as stretchability, have been prepared using solvent-free liquid porphyrins. The fluidic nature of the free-base alkylated-tetraphenylporphyrins was controlled by attaching flexible and bulky branched alkyl chains at different positions. Furthermore, a subtle porphyrin ring distortion that originated from the bulkiness of alkyl chains was observed. Its consequences on the electronic perturbation of the porphyrin-unit were precisely elucidated by spectroscopic techniques and theoretical modelling. This molecular design allows shielding of the porphyrin unit by insulating alkyl chains, which facilitates its corona-charged state for a long period under ambient conditions.


Supplementary Figures
Supplementary Figure 1… Figure 23). Similarly, compounds 1-3 also showed the identical trend of Q-band energy order. However, a large difference between UV-visible absorption peak maxima and their corresponding MCD peak maxima was observed mainly for the vibrational satellites Qx(0,1) and Qy(0,1) which are marked as Q′x(0,1) and Q′y(0,1). These results suggested a probable mixing of these vibrational satellites with the next vibrational components or adjacent Q/Soret components.

Supplementary Figure 25. Molecular intrinsic properties in condensed liquid state.
Comparison of solution (dichloromethane) and solvent-free liquid state UV-visible absorption (a, c, e and g) and the corresponding MCD spectra (b, d, f and h) of compounds 1-4, respectively. The UV-vis absorption spectra were normalized. These spectral analyses reveal a similar spectral feature of solution and solvent-free liquid state in compounds 1-4. Interestingly, the change in the sign sequences of MCD signals follow exactly similar trend under both conditions. Therefore, we conclude that the inherent optoelectronic and structural properties of these porphyrins were also retained in bulk liquid state.  Table 1. Data of UV-visible absorption, emission, glass transition, viscosity and sign variation in MCD of compounds 1-5. The RR frequencies calculated by considering D2d symmetry were found to match closely with the experimentally obtained vibrations. The three highlighted Eu modes were identified as the three newly-appeared RR bands in compounds 2 and 3 (Fig. 4a). For detail analysis of RR spectra see the following section 'assignments of RR bands'.  In the main text, we have discussed that the subtle structural distortion in the porphyrin ring was the main reason for such perturbation in ∆HOMO and ∆LUMO values.

Supplementary
Although the effect is not directly related, this type of structural perturbation that disrupts the orbital angular momentum (OAM) properties of the LUMOs to a greater extent than those of HOMOs, was reported for zinc tetraphenyltetraacenaphthoporphyrin with a saddling distortion. 8 Now the fully electric dipole forbidden Qx(0,0) transition gains intensity only through vibrational borrowing from the allowed B(0,0) band which resulted in concomitant decrease in Soret-band intensity (Fig. 3d)  Picosecond time-resolved fluorescence spectra were recorded with a lab-built time-resolved fluorescence spectrometer. Details of the spectrometer have been published elsewhere. 2,3 Briefly, output of a femtosecond Ti:sapphire laser system (Coherent Micra-5/Legend-Elite USP, 800 nm, 30 fs, 1 kHz) was frequency-doubled and used as the pump pulse. Fluorescence from sample solution was introduced to a 30 cm spectrograph (Acton SP-2358) and detected with a streak camera (Hamamatsu Photonics C10627). A polarization analyzer was set at 54.7 o with respect to the pump polarization for avoiding time-dependent changes of fluorescence intensity due to rotational relaxation. The sample solution was held in a 1 cm quartz cuvette and rapidly stirred with a magnetic stirrer for avoiding accumulation of photodamage in an irradiated volume.
Synthesis. The precursor alkylated-aldehydes 1a-4a (Supplementary Figure 1a) were synthesized by following literature report. 4 After complete purification, the pure aldehydes 1a-4a were further used for the synthesis of targeted porphyrin derivatives (compounds 1-

4).
General synthesis for compounds 1-4. Compounds 1-4 were synthesized by following typical porphyrin condensation reaction between pyrrole and corresponding aldehydes in 1.2:1 mole ratio respectively, refluxing in propionic acid for 4-5 h (Supplementary Figure   1b) in air. 5 The progress of reactions were monitored by UV-vis absorption and thin-layerchromatography (TLC) analysis. After the reaction completed, the propionic acid was distilled off under reduced pressure and the resulting viscus oil was extracted in CHCl3. The crude products were passed through silica-column several times by using 10-20% CH2Cl2 in n-hexane as eluent. An impurity which showed blue spot under UV-light in TLC, was unable to remove through silica-column chromatography purification for large scale products. This impurity was successfully separated by gel permeation chromatography (GPC) in toluene.
However, at this stage, a trace amount of another impurity which always moved together with desired product in TLC, was completely unable to separate by using any chromatographic techniques. Further zinc(II)-metallation of this mixture and subsequent