Er4119hs cavity

Azaphenoxazines and azaphenothiazines were synthesized according to literature procedures with slight modifications (see ESI†). UV-visible spectra were measured with a Cary 100 spectrophotometer equipped with a thermostated 6 × 6 multicell holder. Fluorescence spectra were measured with a BioTek Synergy H1 Hybrid Multi-mode reader. Electron paramagnetic resonance (EPR) spectra were recorded on a Bruker EMXplus (X-band) spectrometer equipped with an ER 4119HS cavity. The radical concentration was determined using the quantitative EPR package of the Bruker Xenon software.

CW-EPR spectra at
the X band (9.44 GHz) were obtained with a Bruker EMX spectrometer
using a high-sensitivity ER4119HS cavity. The microwave power was
13.4 mW, the modulation frequency was 100 kHz, and the modulation
amplitude was 1 G. The averaging number of scans was 20 for the temperature
range of the gel phase and 5 for the temperature range of the fluid
phase. A Bruker BVT-200 variable temperature device was used to control
the sample temperatures. Experiments were performed at least twice,
with samples prepared on different occasions. Empirical data correspond
to the means of experiments with different samples, and standard deviations
of these samples are shown as error bars.
The values of the
maximum (A_max) and minimum (A_min) hyperfine splittings, as well as those of the low
(h₊₁), central (h₀), and high (h_–1) field
line amplitudes were measured directly from spectra (see Figures 3 and 5).
The effective order parameter, S_eff, was calculated from the expression^{27 (link)} where , , A_// (= A_max) is the maximum hyperfine splitting directly
measured in the spectrum, , A_min is the
measured inner hyperfine splitting (see Figure 5), and A_xx, A_yy, and A_zz are the principal values
of the hyperfine tensor for doxylpropane.^{28 (link)} Each experiment was performed at least two times. Error values account
for standard deviations and are presented as error bars when larger
than the symbols.

Spin-labeled samples (10–50uM) were transferred to round glass capillary tubes (0.6 mm ID, 0.8 mm OD; Vitrocom, Inc.) for measurement. The continuous-wave EPR (cw-EPR) spectra were measured utilizing a Bruker EMX spectrometer housing an ER4119HS cavity. For spectral acquisition, the incident microwave power was 2 mW, and the field modulation was 2 G at a frequency of 100 kHz. Each spectrum was acquired with 512 points, corresponding to a spectral range of 100 G, then corrected for background baseline, and intensity normalized following reported protocols (54 (link)).