Laser spectroscopic study on (dibenzo-24-crown-8-ether)–water and –methanol complexes in supersonic jets

Abstract

The conformation and complex formation with guest molecules have been investigated for jet-cooled dibenzo-24-crown-8-ether (DB24C8) by laser induced fluorescence (LIF), UV-UV hole-burning (UV-UV HB), and IR-UV double-resonance (IR-UV DR) spectroscopy. The results are compared with the results of dibenzo-18-crown-6-ether (DB18C6) and analyzed by density functional theory (DFT) calculations at the B3LYP/6-31+G* level. Five conformers are identified for DB24C8 under jet-cooled conditions, and the structure of the major isomer is determined to be a boat form, similar to the case of DB18C6. Two molecules (water and methanol) are investigated as the guest species for the encapsulation experiment. DB24C8 hardly encapsulates a water molecule, different from the case of DB18C6 in which a water molecule is efficiently captured. However, it is likely that larger (water)(n) clusters can be captured in the DB24C8 cavity. The different feature in the complex formation between DB24C8 and DB24C8 with the water molecules are attributed to a larger cavity size of DB24C8 than that of DB18C6. For methanol, two kinds of DB18C6-(methanol)(1) isomers are identified by IR-UV DR spectroscopy; one is the "OH...pi" H-bonded isomer, characteristic of methanol with one OH group, and the other is the "OH...O" H-bonded ones. These results indicate the multiple H-bond formation to the oxygen atoms of the ether ring may play an important role in the complexes of DB24C8 or DB18C6 with water.

Laser Spectroscopic Study of Cold Host–Guest Complexes of Crown Ethers in the Gas Phase

“…We investigate how the structural flexibility affects the dynamics of the inclusion process at the microscopic level. The doublet structure is also observed in DB24C8 [49] but not in B18C6, [46] and is attributed to an exciton splitting [49] due to the interaction of the two benzene chromophores. [47] The UV-UV HB spectra obtained by monitoring bands m1, m2, a, and c-f in Figure 1 b-h indicate that each of these bands can be assigned to the band origin of different species.…”

“…Recently, it has been demonstrated that the laser spectroscopic study of cold gas-phase CEs and their complexes, not only for ionic species [32][33][34][35][36][37][38][39][40][41][42][43] but also the neutral species, [44][45][46][47][48][49][50][51][52] can provide A laser spectroscopic study on the structure and dynamics of cold host-guest inclusion complexes of crown ethers (CEs) with various neutral and ionic species in the gas phase is presented. The complexes with neutral guest species are formed by using supersonic free jets, and those with ionic species are generated with electrospray ionization combined with a cold 22-pole ion trap.…”

“…The CEs chosen are dibenzo-18-crown-6 (DB18C6), [46,47,50,51] benzo-18-crown-6 (B18C6), [46,48] dibenzo-24crown-8 (DB24C8), [49] and 3n-crown-n (n = 4, 5, 6, and 8). The CEs chosen are dibenzo-18-crown-6 (DB18C6), [46,47,50,51] benzo-18-crown-6 (B18C6), [46,48] dibenzo-24crown-8 (DB24C8), [49] and 3n-crown-n (n = 4, 5, 6, and 8).…”

UV photodissociation spectroscopy of cryogenically cooled gas phase host–guest complex ions of crown ethers

“…7a), and DB24C8ÁH + (Fig. 21 The S 1 -S 0 electronic transition of DB24C8ÁH + is roughly 800 cm À1 blueshifted with respect to that of neutral DB24C8. The spectrum of dBAMÁH + ÁDB24C8 shows broad structures with a band origin at B36 350 cm À1 .…”

“…[18][19][20][21][22][23][24][25][26][27] The cold gas phase complexes are generated either by the supersonic expansion technique for neutral complexes [18][19][20][21][22][23][24] or by the electrospray ionization (ESI)/cold ion-trap method for ionic complexes. [18][19][20][21][22][23][24][25][26][27] The cold gas phase complexes are generated either by the supersonic expansion technique for neutral complexes [18][19][20][21][22][23][24] or by the electrospray ionization (ESI)/cold ion-trap method for ionic complexes.…”