Control of H- and J-Aggregate Formation via Host−Guest Complexation using Cucurbituril Hosts

Abstract

The binding interactions between two cyanine dyes, pseudoisocyanine (PIC) and pinacyanol (PIN), and the cucurbit[n]uril hosts, cucurbit[7]uril (CB7) and cucurbit[6]uril (CB6), were investigated by electronic absorption spectroscopy and DFT computational methods. The CB7 host forms more stable complexes with both dyes than CB6 and the computational studies suggest that the cavity of the smaller host CB6 is not threaded by the dyes. The equilibrium association constants (K) for complexation by CB7 were measured and found to be 2.05 x 10(4) and 3.84 x 10(5) M(-1) for PIC and PIN, respectively, in aqueous media at 23 degrees C. CB7 complexation was found to effectively disrupt the intermolecular forces responsible for the aggregation of both dyes. Thus, CB7 completely disrupts the J-aggregates formed by PIC and the H-aggregates (as well as lower concentrations of J-aggregates) formed by PIN. In both cases a competing guest, 1-aminoadamantane (AD), could be used to adjust the extent of aggregation of the cyanine dye. AD regulates aggregate formation because it forms an extremely stable complex with CB7 (K approximately = 10(12) M(-1)) and exerts a tight control on the CB7 concentration available to interact and bind with the dye.

Controlling the Formation of Cyanine Dye H‐ and J‐Aggregates with Cucurbituril Hosts in the Presence of Anionic Polyelectrolytes

“…[12] Intrigued by our initial results, we are further exploring the idea of controlling dye aggregation through host-guest chemistry. In the present work, we show the effects of PSS on the development of J-and H-aggregates for two cyanine dyes, pseudoisocyanine (PIC) and pinacyanol (PIN), and demonstrate that the extent of formation of the aggregates can be controlled by using the host-guest association equilibrium between CB7 and the dye molecules.…”

The Use of Spectrophotometry UV-Vis for the Study of Porphyrins

“…Due to the distinct optical properties, also the control of the formation of H-and J-aggregated states of dyes has attracted much research interest (Maiti et al, 1998;Shirakawa et al, 2003;De Luca et al, 2006;Egawa et al, 2007;Yagai et al, 2008;Gadde et al, 2008;Ghosh et al, 2008;Zhao et al, 2008;Delbosc et al, 2010).…”

Solvent‐Induced Structural Transition of Self‐Assembled Dipeptide: From Organogels to Microcrystals

“…This red shift suggests an effective p-p stacking between the aromatic residues of FF dipeptide molecules, indicating the possible formation of a J-aggregate in the gel. [51][52][53][54][55] In contrast to the gels, the microcrystals obtained with ethanol content of 25, 70, and 100 % have the same emission peak at about 285 nm. Compared with the emission spectra of the FF solution and xerogel in toluene, the blue shift possibly indicates a characteristic of an extended H-aggregate between the phenyl rings in the microcrystals.…”

“…Compared with the emission spectra of the FF solution and xerogel in toluene, the blue shift possibly indicates a characteristic of an extended H-aggregate between the phenyl rings in the microcrystals. [51][52][53][54][55] In addition, to get a more clear idea about the organization mode of FF aromatic residues, we monitored their absorption spectra in the gel and in absolute ethanol ( Figure S4 in the Supporting Information). In comparison with the maximum absorption of free FF molecules (259 nm), a considerable blue shift in ethanol (222 nm) and a red-shifted shoulder around 285 nm in gel further support the conclusions drawn from the emission spectra.…”

“…In comparison with the maximum absorption of free FF molecules (259 nm), a considerable blue shift in ethanol (222 nm) and a red-shifted shoulder around 285 nm in gel further support the conclusions drawn from the emission spectra. [51][52][53][54][55] X-ray diffraction was used to evaluate the molecular assembly in different samples ( Figure 5). Only one sharp peak at 2q of 5.22 or 5.528, corresponding to d spacing of 16.9 or 15.9 , was observed for the xerogel formed in toluene (Figure 5 a) and 10 % ethanol/toluene mixture ( Figure 5 b), respectively.…”