Cyclic water pentamer in a tape-like structure

Abstract

A novel water tape consisting of fused cyclic water pentamers has been observed in a supramolecular compound.

Water Pentamer: Characterization of the Torsional-Puckering Manifold by Terahertz VRT Spectroscopy

“…Coriolis coupling had already been observed in the dimer, 14 trimer, 23 and tetramer, 24 but first-order Coriolis splittings, such as those in the (H 2 O) 5 pentamer band, were originally predicted to be vanishingly small 25,26 for cyclic water clusters. Nonetheless, analysis of the extensive water trimer data set, with its linear Coriolis splittings, had already forced a revision of this thinking.…”

“…Liu et al observed the first (D 2 O) 5 VRT band in 1997 by Terahertz laser spectroscopy. 13 Whereas previous high-resolution VRT experiments on the water dimer, 14 trimer, 15 and hexamer 16 had shown that HBNR dynamics occurring within these water clusters were manifested as small tunneling splittings of each rovibrational transition (Figure 2), the parallel (∆K ) 0) band, measured by Liu et al at 81.2 cm -1 , as well as an additional parallel band measured shortly thereafter at 30.2 cm -1 by Cruzan et al, 11 were both devoid of observable bifurcation tunneling splittings.…”

“…13 Whereas previous high-resolution VRT experiments on the water dimer, 14 trimer, 15 and hexamer 16 had shown that HBNR dynamics occurring within these water clusters were manifested as small tunneling splittings of each rovibrational transition (Figure 2), the parallel (∆K ) 0) band, measured by Liu et al at 81.2 cm -1 , as well as an additional parallel band measured shortly thereafter at 30.2 cm -1 by Cruzan et al, 11 were both devoid of observable bifurcation tunneling splittings. It was not until Brown et al reported the first (H 2 O) 5 band at 89.0 cm -1 , wherein each rovibrational transition was split into four observable lines separated by 4.8 MHz, that the bifurcation tunneling splittings, predicted by theoretical efforts, [17][18][19] were observed in the water pentamer ( Figure 3). 12 The observed bifurcation tunneling splittings in the (H 2 O) 5 water pentamer were, however, 60 times smaller than those of the typical torsional (H 2 O) 3 trimer (Table 1).…”

“…The 89.0 cm -1 (H 2 O) 5 band provided not only the first analysis of water pentamer bifurcation tunneling dynamics but also the first insight into its Coriolis perturbations. Coriolis coupling had already been observed in the dimer, 14 trimer, 23 and tetramer, 24 but first-order Coriolis splittings, such as those in the (H 2 O) 5 pentamer band, were originally predicted to be vanishingly small 25,26 for cyclic water clusters.…”

“…Once Viant et al employed both the unexpected first-order and the second-order Coriolis effects to characterize the perturbed water trimer bands, a highly accurate (root-mean-sqare (rms) ) 1.36 MHz) global fit of 9 (D 2 O) 3 pseudorotational bands comprising 554 individual VRT transitions was obtained (Figure 4). 29 Brown et al quickly followed with a global fit of the (H 2 O) 3 data, 30 then subsequently used first-order Coriolis effects to successfully fit the 89.0 cm -1 (H 2 O) 5 band, noting however that second-order Coriolis terms were not needed. 12 We report here the analysis of five new (D 2 O) 5 bands, three of which exhibit a linear Coriolis splitting similar to that of the (H 2 O) 5 band.…”