spectrum of ligand 7 showed NH and CO vibration stretching peaks
at 3287 and 1650 cm1 respectively. Electrospray ionization mass
spectra (ESI-MS) of linear bis-pyridine ligand 7 exhibited a peak
of m/z at 347.14 corresponding to [M+H+] as shown in Fig. S3 further
approved its successful preparation. Similarly, the proton
NMR spectrum of bent bis-amide functionality ligand 10 showed
one sharp singlet for the NH at d 10.65 ppm in dimethyl sulfoxide
(DMSO-d6) (Fig. S2) and a peak for the amide carbon around
160 ppm in the 13C NMR spectrum. Infrared spectrum of ligand
10 showed the NH and CO vibration stretching peaks for the amide
linkage at 3274 cm1 and 1630 cm1 respectively. The electrospray
ionization mass spectra (ESI-MS) of 10 confirmed the formation of
amide linkers and showed a m/z peak at 325.05 corresponds to [M
+H+] (Fig. S3).