13C NMR investigations and order parameters of rod-like molecules with terminal phenyl and thiophene rings in mesogenic core✰

Influence of the Thiophene Ring on the Molecular Order of Structurally Simple π‐Conjugated Smectogens: 13C NMR Study

“…Thus the insertion of fluorenone into the rigid core not only brings π‐conjugated properties to the molecule but also may favor fascinating phases, as recently noticed [49] . Interestingly, our earlier studies showed that when thiophene is part of the rigid core and linked to the phenyl ring via linking groups such as ester or imine, the order parameters of thiophene and phenyl rings regularly exhibited dissimilarity independent of the mesophase [30,31,34,52] . In the present case, except for Thio‐3, the order parameters of thiophene and phenyl ring (Thio‐1 and Thio‐2) remain the same and are independent of the mesophase.…”

“…The 13 C NMR studies of liquid crystalline molecules [23,24] and their π‐conjugated counterparts [25–27] are increasingly witnessed owing to the versatility in mapping the orientational constraints of moieties inherent to the mesogens. The work emanated from our group unambiguously established the utility of 13 C NMR for probing thiophene‐based molecular mesogens [28–34] . In this work, we extend the efficacy of 13 C NMR spectroscopy to determine the molecular order of structurally simple π‐conjugated liquid crystalline molecules in which thiophene is the important fragment of the rigid core.…”

“…The work emanated from our group unambiguously established the utility of 13 C NMR for probing thiophene-based molecular mesogens. [28][29][30][31][32][33][34] In this work, we extend the efficacy of 13 C NMR spectroscopy to determine the molecular order of structurally simple πconjugated liquid crystalline molecules in which thiophene is the important fragment of the rigid core.…”

Direct method to grasp molecular topology of mesogens through13C–1H dipolar couplings

“…The order parameter values obtained for R1 in SmC and SmI phases are consistent with the literature data. 13,31 For instance, Catalano et al carried out 2 H NMR studies on ( S )-[4-(2-methylbutyl)phenyl]-4′-octylbiphenyl carboxylate, 32 a smectogen exhibiting polymesomorphsim, reported the orientational order parameters of the phenyl ring of the core unit in smectic mesophases including SmI phase and the values are consistent with R1 data. Domenici et al 33 also used the 2 H NMR for finding the orientational order parameter of a ferroelectric smectogen namely (+)-( S )-4-[4′-(1-methylheptyloxy)] biphenyl 4-(10-undecenyloxy)benzoate and the order parameters of the phenyl ring are comparable with the values found for R1 mesogen.…”

“…The order parameter values obtained for R1 in SmC and SmI phases are consistent with the literature data. 13,31 For instance, Catalano et al that the long axis passes through the centers of four phenyl rings of the core unit, as all the rings exhibit similar order parameter values (Table 2). In the case of the L1 mesogen, which deviates from a rod-like shape owing to the presence of a phenyl ring in the lateral location, the order parameters in the nematic phase show variation (Table 3).…”