11210
J. Phys. Chem. A 2010, 114, 11210–11215
Structural Evolution of (1-NpOH)n Clusters Studied by R2PI and IR Dip Spectroscopies† Morihisa Saeki,‡ Shun-ichi Ishiuchi,§ Makoto Sakai,§ Kenro Hashimoto,| and Masaaki Fujii*,§ Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan UniVersity, 1-1 minami-Osawa, Hachioji, 192-0397, Japan ReceiVed: March 30, 2010; ReVised Manuscript ReceiVed: August 11, 2010
A large-size 1-naphthol cluster, (1-NpOH)n, with n e 30 was prepared by using a high-pressure pulsed valve. The electronic and vibrational transitions of (1-NpOH)n with n ) 3-9 were measured by resonant twophoton ionization (R2PI) and ion-detected IR dip spectroscopies. The S1 r S0 R2PI spectrum shows partially resolved structures around the origin band in the (1-NpOH)n cluster with n ) 3-8. The (1-NpOH)3 and the (1-NpOH)6 clusters show relatively sharp origin bands. The structure of (1-NpOH)3 was determined by comparison of the IR dip spectrum with the simulated one by DFT calculation, while those of (1-NpOH)n (n g 4) were discussed in terms of topological geometries of a hydrogen-bonded network. Those analyses suggest that (i) the (1-NpOH)3 cluster has the cyclic structure where three 1-NpOH monomers are linked by both the hydrogen-bonding and the π · · · C-H interaction between naphthyl rings and (ii) the (1-NpOH)n cluster with n g 4 is built up by attaching the 1-NpOH monomers to the (1-NpOH)3 core. I. Introduction A cluster that consists of a few to a few tens of molecules corresponds to a nanodroplet of a solution, or the core of a crystal by various intermolecular interaction at low temperature, and thus its nature is important to understand the condensed phase from a molecular viewpoint. During the past decade, the structures of large hydrogen-bonded clusters, such as a protonated water cluster, have been extensively studied by using vibrational and electronic spectroscopies.1-19 The hydrogenbonded network of protonated water clusters has been revealed according to the size of the cluster by IR spectroscopy. Its topological structure is a small-size chain (n e 10),3-5 and it develops into a two-dimensional net structure (∼10 < n < 21) and then evolves into a nanometer-scaled cage (n g 21).7-10 A further structural study on a larger cluster is still in progress; however, the structural evolution of a pure hydrogen bonded cluster is becoming clear. In contrast to a pure hydrogen-bonded cluster, there have been a few studies on the large clusters that are formed by the hydrogen bonding and other intermolecular forces. Recent studies on biological molecules and clusters have suggested the importance of cooperation between the hydrogen bonding and the stacking interaction (also called the π-π interaction).20-29 We are motivated to understand such cooperation by using a simple benchmark system and have started a structural study on a 1-naphthol cluster, (1-NpOH)n. A previous study showed that the (1-NpOH)2 cluster is formed by cooperation between the hydrogen bonding and the stacking interaction.30 This indicates the (1-NpOH)n cluster is a good benchmark for the hydrogen-bonding/stacking cooperation. In this study, we report on the generation of large-size (1-NpOH)n clusters with n e 30 †
Part of the “Klaus Mu¨ller-Dethlefs Festschrift”. * Author to whom correspondence should be addressed. Phone/Fax Number: +81-45-924-5250. E-mail address:
[email protected]. ‡ Japan Atomic Energy Agency. § Tokyo Institute of Technology. | Tokyo Metropolitan University.
and spectroscopic investigation of the (1-NpOH)n clusters with n ) 3-9 by resonant two-photon ionization (R2PI) and iondetected IR dip spectroscopy. Comparison of the IR spectra between the (1-NpOH)n clusters and the 1-NpOH monocrystal gives us information on the structural difference between them. The structure of (1-NpOH)3 is determined by comparison of the IR dip spectrum with the simulated one by density functional theory (DFT) calculation, while those of (1-NpOH)n (n g 4) are discussed by building up topological geometries of a hydrogen-bonded network. The correlation of evolution of the R2PI spectra with the cluster structures is also discussed. II. Experimental Section The experimental apparatus was presented in a previous paper.30 A cluster was generated by passing 7 atm of neon gas through a heated reservoir of 1-NpOH (100-120 °C) in a pulsed nozzle (Even-Lavie valve system; 250 mm diameter orifice).31 The pulsed nozzle was operated at 20 Hz. As is the case concerning the experiment of (1-NpOH)2, complete dehydrization in a sample line was performed so as to avoid the formation of (1-NpOH)2(H2O)n clusters, which contaminate the spectrum of (1-NpOH)n.30 The cluster beam was skimmed at 20 mm downstream from the pulsed nozzle. The cluster in the skimmed beam was ionized by two-photon ionization. The generated ion was introduced into a time-of-flight mass spectrometer through ion optics and detected by a microchannel plate. Here, a high electric field at up to 7000 V/cm was applied to detect any large and heavy clusters. The pulse duration of the Even-Lavie valve system and the relative position between the valve and the skimmer were adjusted so as to prepare cold clusters of 1-NpOH. The method of the R2PI and ion-detected IR dip spectroscopy have been described elsewhere.30,32-34 Briefly, the S1 r S0 R2PI spectrum was measured by monitoring the intensity of ions of (1-NpOH)n as a function of the wavelength of the laser. In a measurement of the R2PI spectra the laser power was sufficiently weakened so as to avoid nonresonant ionization. In IR dip spectroscopy, an IR laser pulse was irradiated to the (1-
10.1021/jp102849q 2010 American Chemical Society Published on Web 09/08/2010
Structural Evolution of (1-NpOH)n Clusters
J. Phys. Chem. A, Vol. 114, No. 42, 2010 11211
Figure 1. Mass spectrum of the (1-NpOH)n clusters prepared by nonresonant and two-photon ionization. The ionization was performed using high-power UV light with an energy of 31 305 cm-1.
NpOH)n prior to irradiation by the ionization laser, of which the wavelength was fixed at the strongest electronic bands around the origin of the S1 r S0 transition. By monitoring the intensity of the ions of (1-NpOH)n, we scanned the wavelength of infrared light. When the frequency of the IR light matched the transition to a certain vibrational level, the ion current decreased because of a loss of population from the ground vibrational state. Thus, the IR absorption could be detected by depletion of the ion current. III. Results A. Mass Spectrum and R2PI Spectrum of (1-NpOH)n. Figure 1 shows the mass spectrum of the (1-NpOH)n clusters prepared by nonresonant two-photon ionization. Intense UV light of 31 305 cm-1 was used to obtain a sufficient two-photon ionization signal. The mass spectrum shows that large (1NpOH)n clusters are generated up to at least n ) 30, which would be almost the largest cluster of neutral organic molecules so far reported. This shows that a high-pressure expansion of the sample vapor is effective to generate a larger cluster. The signal gradually decreases with an increase of the number of molecules, n; the magic number is not clear. Figure 2 shows the S1 r S0 R2PI spectra of (1-NpOH)n with n ) 3-9 in the region 30 530-32 240 cm-1. The 1-NpOH molecule has trans- and cis-isomers, but the cis-1-NpOH isomer was negligible under the present condition.30 The vibronic bands in this region are attributed to the Lb π-π* transition of the 1-NpOH molecules.35,36 We tentatively assigned the origins of the electronic transitions, which are indicated by arrows in Figure 2. The frequencies of the origin bands are listed in Table 1. All origin bands are 70-300 cm-1 red-shifted from the origin band of the 1-NpOH monomer at 31 457 cm-1. The R2PI spectra show the structured transitions in the (1-NpOH)n clusters with n ) 3-8, although it becomes structureless for (1-NpOH)9. This suggests that the prepared clusters in the experiment were sufficiently cooled for a size of at least n ) 3-8. The electronic excitation and ionization of a large molecular cluster often leads to evaporation of the component molecules. Thus, the R2PI spectra of the smaller-size clusters are contaminated by the signal of the larger clusters in spite of a massselected measurement. Such contamination may be found in the spectra of (1-NpOH)3 (Figure 2a). A weak shoulder of the origin (31 318 cm-1) is close to a strong peak at 31 311 cm-1 in the spectrum of the (1-NpOH)4 cluster (Figure 2b). It may be due to evaporation of (1-NpOH)4. The spectral component due to evaporation may contribute to the spectra in others. However, the contribution of the evaporation is small sufficiently because
Figure 2. S1 r S0 R2PI spectra of (1-NpOH)n with sizes n ) 3-9. The arrows indicate the origin of the electronic bands.
TABLE 1: Origin Bands of the Electronic Spectrum and the Vibrational Bands in (1-NpOH)n with Sizes n ) 3-9 cluster
origin band (cm-1)
n)3 n)4 n)5 n)6 n)7 n)8 n)9
31380 31150 31250 31350 31160 31180 ∼31250
vibrational bands (cm-1) 3431 3349 3202 3194 3238 ∼3300 ∼3250
3380 3249 3267 3313
3401 3322
the observed peaks in the spectra are mostly independent in each spectrum, except for those of (1-NpOH)3 and (1-NpOH)4 described above. Thus, we suppose that the main structure in each R2PI spectra represents the electronic transition of a cluster of specific size. As can be seen in the figure, the (1-NpOH)3 and (1-NpOH)6 clusters show relatively sharp origin bands in the S1 r S0 R2PI spectra (Figure 2a,d), while other clusters represent lowfrequency bands, or broader structure around origins. This suggests that the (1-NpOH)3 and (1-NpOH)6 clusters maintain their structures upon electronic excitation. This contrast is discussed in terms of the structure of clusters later.
11212
J. Phys. Chem. A, Vol. 114, No. 42, 2010
Saeki et al.
Figure 4. Stable structures of (1-NpOH)2 and (1-NpOH)3 in the M062X/6-31++G(d,p) calculation. The binding energies (kcal/mol) are given under each structure. The point group is indicated in parentheses.
Figure 3. IR dip spectra of (1-NpOH)n with sizes n ) 3-9. The spectra were obtained by fixing the UV laser to the origin bands, respectively.
B. IR Dip Spectrum of (1-NpOH)n. Figure 3 shows the IR dip spectra of (1-NpOH)n with n ) 3-9 in the region 2800-3750 cm-1. In the IR dip spectrum of (1-NpOH)230 and 1-NpOH(ROH)n (R ) Me, Et, t-Bu; n ) 1-3),33 we have assigned the vibrational bands at around 3050 cm-1 to CH stretching, and those in the region 3100-3700 cm-1 to OH stretching. The vibrational band of the OH stretching was observed at 3655 cm-1 in the bare 1-NpOH monomer and is red-shifted by the formation of hydrogen bonding.30,32,33 Thus, the vibrational bands in the region 3100-3500 cm-1 in Figure 3 are assigned to hydrogen-bonded OH stretching. The frequencies of the hydrogen-bonded OH stretching are also listed in Table 1. It should be noted that vibrational bands are absent at around the free OH stretching region (3655 cm-1). This is discussed in section IVA. IV. Discussion A. Comparison of the Structures between the 1-NpOH Clusters and the 1-NpOH Monocrystal. The observed vibrational bands in Figure 3 are assignable to either CH or OH stretching vibration from their frequencies. The frequency of the CH stretching vibration, located at around 3060 cm-1, is independent of the cluster size. All the OH stretching vibrations in (1-NpOH)n with n ) 3-9 are red-shifted from the free OH stretching one, which locates at 3655 cm-1 in the 1-NpOH monomer. This means that all OH moieties are hydrogen-bonded
to other OH ones or naphthyl rings in (1-NpOH)n with n g 3. A structural study using X-ray diffraction has elucidated that the 1-NpOH monocrystal was composed of chains of 1-NpOH molecules, which were linked by hydrogen bonding.37 If the 1-NpOH clusters have a chain structure, they should have a free OH bond at the terminal molecule. The absence of a free OH bond suggests that the structure of the (1-NpOH)n clusters is not a chain and is different from that of the monocrystal. This means that the (1-NpOH)n cluster will be a metastable structure, likely to be a pseudocrystal from the viewpoint of the crystal.38 The structural difference of the clusters and the monocrystal is attributed to the difference in the growing-up condition, such as the temperature, pressure, or existence of solvent molecules. The contribution of solvent molecules for the growing-up process has been well studied in polymorphism,39-42 and thus a structural study on a large cluster containing the solvent molecules should be important in future work. B. Structural Determination of (1-NpOH)3 Based on DFT Calculation. The geometries, binding energies, and harmonic wavenumbers of (1-NpOH)3 were investigated by the density functional theory (DFT) calculations using the Gaussian-09 program.43 Previous study on (1-NpOH)2 suggested that dispersion force must be considered in the calculation of the (1-NpOH)n clusters, but the MP2 calculation with a large basis set is a very heavy process.30 In this study, we employed the M062X functional developed by Zhao and Truhlar,44 which is a dispersion-corrected DFT method and more economical than the MP2 calculation, with the standard 6-31++G(d,p) basis sets. The optimized structures of (1-NpOH)2 and (1-NpOH)3 are shown in Figure 4. The binding energies are given under each structure. They are corrected by the zero-point energies by the calculated harmonic frequencies and by the counterpoise method45 for the basis set superposition errors. The calculated wavenumbers of the OH stretch vibrations are listed in Table 2. The scale factor, 0.937, was determined by the ratio of the observed and the calculated harmonic wavenumbers. The calculated intensities of the vibrations are also given. Prior to (1-NpOH)3, we discuss calculated results of (1NpOH)2 to confirm the reliability of the M062X/6-31++G(d,p) calculation. In a previous study, we concluded that the (1NpOH)2 cluster is stabilized by both hydrogen bonding and stacking interaction, and it has the structure 2a or 2b shown in Figure 4.30 The calculated wavenumbers of OH stretching at the M062X/6-31++G(d,p) are 3597 and 3645 cm-1 for 2a and 3585 and 3640 cm-1 for 2b. They show good agreement with
Structural Evolution of (1-NpOH)n Clusters
J. Phys. Chem. A, Vol. 114, No. 42, 2010 11213
TABLE 2: Calculated Wavenumbers (cm-1) of the OH Stretch for (1-NpOH)2 and (1-NpOH)3 at the M062X/ 6-31++G(d,p) Level, Together with Experimental Values (IR Intensities (kM/mol) in Parentheses) (1-NpOH)2
(1-NpOH)3
expa
2a
2b
exp
3a
3b
3b
3646
3645 (67) 3597 (125)
3640 (92) 3585 (181)
3431
3477 (774) 3477 (772) 3438 (10)
3577 (238) 3427 (764) 3363 (419)
3631 (66) 3591 (106) 3550 (231)
3606
a
Reference 30.
Figure 5. Observed (top) and calculated IR spectra of (1-NpOH)3 for structures 3a, 3b, and 3c. The structures are illustrated beside the calculated spectra. -1
the experimental values, 3606 and 3646 cm , with an error of less than 0.6%. We confirmed that the results at M062X/631++G(d,p) are available for the structural determination of the (1-NpOH)n cluster. In the (1-NpOH)3 cluster, we found three stable structures, which are 3a-3c in Figure 4. Focusing on the hydrogen-bonded network, we can classify structure 3a as cyclic and structures 3b and 3c as chains. We also performed the optimization by employing the cyclic type where one naphthyl ring repels others by steric hindrance as the initial geometry, but it finally changed to structure 3b. The absence of the cyclic type where one naphthyl ring repels others suggests the attractive force works between naphthyl rings. In structure 3a three 1-NpOH monomers are linked by both the hydrogen bonding and the π · · · C-H interaction between the naphthyl rings. At first glace, structure 3b seems to be cyclic type but has the terminal OH moiety that interacts with a naphthyl ring through π · · · O-H bonding. In structure 3c the 1-NpOH monomers are stacked on each other and are linked by hydrogen bonding. As described in section IVA, structure 3c is regarded as a microscopic model of the 1-NpOH monocrystal. The binding energy decreases in the order 3a > 3b > 3c. Figure 5 shows the comparison of the IR dip spectrum of (1-NpOH)3 with the simulated one by the DFT calculation. The simulated spectrum was created from Table 2. The simulated spectrum of structure 3a shows the appearance of a doubly
Figure 6. Built-up topological structures of (1-NpOH)n with sizes n ) 3-7. The broken lines indicate the stacking interaction, while the gray lines indicate hydrogen bonding.
degenerate transition of the OH stretch at 3478 cm-1 with high intensity, while those of structures 3b and 3c suggest the appearance of three vaibrational bands in the region 3350-3650 cm-1. Only the spectrum of structure 3a reproduces the observed one. Thus, we concluded that the (1-NpOH)3 cluster has structure 3a, where all the monomers form cyclic hydrogenbonded networks. C. Building Up of Topological Structures of (1-NpOH)n. The computations of the higher clusters are so demanding that we could not evaluate either the stability or the wavenumbers of the vibrational transitions of the isomers for n g 4 with current computational power. However, it is possible to argue the further aggregation of (1-NpOH)n from the topological point of view, based on the positions of the observed bands and their shifts in the n g 3 spectra. Figure 6 shows the built-up process of topological structures of (1-NpOH)n. In the (NpOH)3 cluster the assigned structure 3a in Figure 4 is described as 3. Here, we would like to denote the proton-donating O atoms as OD and the proton-accepting ones as OA. The ODA notation means that the O atom is both a proton donor and an acceptor, while the ODAA notation indicates that the O atom donates one proton and accepts two protons. With this notation, all of the OH moieties in structure 3 belong
11214
J. Phys. Chem. A, Vol. 114, No. 42, 2010
to the ODAH types. It corresponds to a single OH stretching in the IR dip spectrum (Figure 3a). In the (1-NpOH)4 cluster we built up the structures 4-1 and 4-2 based on the idea that the attractive force works between the naphthyl rings. Both structures 4-1 and 4-2 satisfy an absence of the free OH band. Structure 4-1 is composed of the (1-NpOH)3 core and exterior 1-NpOH monomer. On the basis of the structure of (1-NpOH)2, the 1-NpOH molecule can be attached to the (1-NpOH)3 core, not only by hydrogen bonding but also by the stacking interaction. The OH moieties in structure 4-1 are classified into the ODAAH, ODAH, and ODH types. Three kinds of OH moieties in structure 4-1 are consistent with the presence of three vibrational bands at 3349, 3380, and 3401 cm-1 in the IR dip spectrum (see Figure 3b). On the other hand, structure 4-2 has a cyclic hydrogen-bonded structure. In this structure, four OH moieties are equivalent and are classified into the same ODAH type. This is not consistent with the three vibrational bands in the IR spectrum based on a zeroth-order approach. Therefore, we concluded that the (1NpOH)4 cluster has structure 4-1. From the analogy to (1-NpOH)4, we can assume the structure of the (1-NpOH)5 cluster is composed of the (1-NpOH)3 cluster core and two exterior 1-NpOH molecules (see Figure 4d). The OH moieties in structure 5 are classified into the ODAAH, ODAH, and ODH types. The existence of three kinds of OH moieties is consistent with the presence of three vibrational bands at 3202, 3249, and 3322 cm-1 in the IR dip spectrum of (1-NpOH)5. According to the building-up recipe in (1-NpOH)4 and (1NpOH)5, the (1-NpOH)6 cluster has structure 6, where the (1NpOH)3 core is solvated by three 1-NpOH molecules. Structure 6 has two kinds of the OH moieties, which are classified into the ODAAH and ODH types. This is consistent with the IR dip spectrum of (1-NpOH)6, in which two OH vibrational bands are observed at 3194 and 3267 cm-1. According to the building-up recipe in the smaller size, the (1-NpOH)7 cluster would be structure 7 in which one more NpOH molecule is solvated on the (NpOH)6 core. Structure 7 has three kinds of OH moieties that are classified into the ODAAH, ODAH, and ODH types. However, the IR dip spectrum of the (1-NpOH)7 cluster shows only two vibrational bands at 3238 and 3313 cm-1, as shown in Figure 3e. Thus, we cannot directly apply the building-up recipe to explain the spectral feature. It may be due to the weak intensity of one of the OH stretching vibrations. In the IR spectrum of (1-NpOH)5, one of the OH stretching vibrations is weak. Similarly, one of the OH stretching vibrations in (1-NpOH)7 may be very weak for our sensitivity of the IR dip spectroscopy. Different kinds of information, such as the mid-infrared spectrum, are needed to determine the geometry of the (1-NpOH)n cluster with n g 7. D. Evolution of the R2PI Spectra of (1-NpOH)n. The spectral shift in electronic transitions of hydrogen-bonded clusters is often discussed in terms of the strength of the hydrogen bonding. The electronic transition of a solvated 1-NpOH cluster also shows a red shift according to the proton affinity of the solvent and the number of solvent molecules. For example, the origin of the S1-S0 transition of the 1-NpOH(MeOH)n shifts to red monotonically with an increase of solvent molecules (-158, -218, and -252 cm-1 from monomer for n ) 1-3, respectively).33 One may also expect a similar monotonical red shift in the S1-S0 transition of (1-NpOH)n. However, as can be seen in Figure 2 and Table 1, the shift of the origin band is largely different from other solvated 1-NpOH clusters. For (1-NpOH)3 the origin is red-shifted -77 cm-1 from the monomer (31 457 cm-1).32,33 The electronic transition is
Saeki et al. further shifted to red in going from (1-NpOH)3 to (1-NpOH)4 (-307 cm-1 from the monomer); however, the origin comes back to blue at (1-NpOH)5 and (1-NpOH)6 (-207 and -107 cm-1 from the monomer). Such an irregular shift is difficult to understand on the basis of only solvation by hydrogen bonding. In the case of the dimer, in which both the hydrogen bonding and the stacking interaction work cooperatively and present the red shift in the S1-S0 transition,30 the stacking interaction is thus not adequate to explain the blue shift. The irregular shift suggests a mixing of two different ππ* states (La and Lb) by solvation and/or Davydov splitting of the electronic states caused by an equivalent naphthyl ring.46,47 Another characteristic feature of the R2PI spectra of (1NpOH)n is sharpness of the origin band for (1-NpOH)3 and (1NpOH)6. This is consistent with the structural evolution discussed in the previous section. The (1-NpOH)3 and (1NpOH)6 clusters have the most symmetric structure, and the symmetry is C3 the group when the attractive force works between naphthyl rings (structure 3a in Figure 4 and structure 6 in Figure 6). Under C3 symmetry, the electronic transition from the ground state with A symmetry to the excited state of A symmetry is allowed, but that to the excited state of the E symmetric species is forbidden. On the other hand, the symmetry of other clusters is C1, and all of the electronic states are allowed. If the observed spectra consist of several electronic states originating from the electronic mixing and splitting, the observed sharpness of (1-NpOH)3 and (1-NpOH)6 is consistent because of a symmetry restriction. V. Conclusions We successfully generated (1-NpOH)n clusters with n e 30 by using a high-pressure pulsed valve, and measured the S1 r S0 R2PI spectrum and the IR dip spectrum of (1-NpOH)n with n ) 3-9. The absence of free OH stretching vibration in the IR dip spectra elucidates that the structures of (1-NpOH)n are different from that of the 1-NpOH monocrystal. The structure of (1-NpOH)3 was determined by comparison of the IR dip spectrum with the simulated one at the M062X/6-31++G(d,p) level, while those of (1-NpOH)n (n g 4) were discussed by building up topological structures of a hydrogen-bonded network. Those analyses suggest that (i) the (1-NpOH)3 cluster has the cyclic structure where three 1-NpOH monomers are linked by both the hydrogen-bonding and the π · · · C-H interaction between naphthyl rings and (ii) the (1-NpOH)n cluster with n g 4 is built up by attaching the 1-NpOH monomers to the (1-NpOH)3 core. Acknowledgment. We are grateful to Professor A. Nakajima of Keio University for his experimental advice. We also express our gratitude to Professor N. Mikami in Tohoku University for his support by providing the apparatus. This work is supported in part by a program entitled “Research for the Future (RFTF)” of the Japan Society for the Promotion of Science (No. 98P01203) and a Grant-in-Aid for Scientific Research “KAKENHI” in the priority area “Molecular Science for Supra Functional Systems” from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan. References and Notes (1) Castleman, A. W., Jr.; Bowen, K. H., Jr. J. Phys. Chem. 1996, 100, 12911. (2) Bondybey, V. E.; Beyer, M. K. Int. ReV. Phys. Chem. 2002, 21, 277. (3) Yeh, L. I.; Okumura, M.; Myers, J. D.; Price, J. M.; Lee, Y. T. J. Chem. Phys. 1989, 91, 7319.
Structural Evolution of (1-NpOH)n Clusters (4) Okumura, M.; Yeh, L. I.; Myers, J. D.; Lee, Y. T. J. Phys. Chem. 1990, 94, 3416. (5) Jiang, J.-C.; Wang, Y.-S.; Chang, H.-C.; Lin, S. H.; Lee, Y. T.; Niedner-Schatteburg, G.; Chang, H.-C. J. Am. Chem. Soc. 2000, 122, 1398. (6) Lin, C.-K.; Wu, C.-C.; Wang, Y.-S.; Lee, Y. T.; Chang, H.-C.; Kuo, J.-L.; Klein, M. L. Phys. Chem. Chem. Phys. 2005, 7, 938. (7) Chang, H.-C.; Wu, C.-C.; Kuo, J.-L. Int. ReV. Phys. Chem. 2005, 24, 553. (8) Miyazaki, M.; Fujii, A.; Ebata, T.; Mikami, N. Science 2004, 304, 1134. (9) Shin, J.-W.; Hammer, N. I.; Diken, E. G.; Johnson, M. A.; Walters, R. S.; Jaeger, T. D.; Duncan, M. A.; Christie, R. A.; Jordan, K. D. Science 2004, 304, 1137. (10) Wu, C.-C.; Lin, C.-K.; Chang, H.-C.; Jiang, J.-C.; Kuo, J.-L.; Klein, M. L. J. Chem. Phys. 2005, 122, 074315. (11) Headrick, J. M.; Diken, E. G.; Walters, R. S.; Hammer, N. I.; Christie, R. A.; Cui, J.; Myshakin, E. M.; Duncan, M. A.; Johnson, M. A.; Jordan, K. D. Science 2005, 308, 1765. (12) Lisy, J. M. J. Chem. Phys. 2006, 125, 132302. (13) Kuo, J.-L.; Klein, M. L. J. Chem. Phys. 2005, 122, 024516. (14) James, T.; Wales, D. J. J. Chem. Phys. 2005, 122, 134306. (15) Iyengar, S. S.; Day, T. J. F.; Voth, G. A. Int. J. Mass. Spectrom. 2005, 241, 197. (16) Iyengar, S. S.; Petersen, M. K.; Day, T. J. F.; Burnham, C. J.; Teige, V. E.; Voth, G. A. J. Chem. Phys. 2005, 123, 084309. (17) Burnham, C. J.; Petersen, M. K.; Day, T. J. F.; Iyengar, S. S.; Voth, G. A. J. Chem. Phys. 2006, 124, 024327. (18) Singh, N. J.; Park, M.; Min, S. K.; Suh, S. B.; Kim, K. S. Angew. Chem., Int. Ed. 2006, 45, 3795. (19) Mizuse, K.; Fujii, A.; Mikami, N. J. Chem. Phys. 2007, 126, 231101. (20) Nir, E.; Kleinermanns, K.; de Vries, M. S. Nature (London) 2000, 408, 949. (21) Nir, E.; Janzen, C.; Imhof, P.; Kleinermanns, K.; de Vries, M. S. Phys. Chem. Chem. Phys. 2002, 4, 732. (22) Plu¨tzer, C.; Kleinermanns, K. Phys. Chem. Chem. Phys. 2002, 4, 4877. (23) Bakker, J. M.; Compagnon, I.; Meijer, G.; von Helden, G.; Kabela´cˇ, M.; Hobza, P.; de Vries, M. S. Phys. Chem. Chem. Phys. 2004, 6, 2810. (24) Guerra, C. F.; Bickelhaupt, F. M.; Snijders, J. G.; Baerends, E. J. J. Am. Chem. Soc. 2000, 122, 4117.
J. Phys. Chem. A, Vol. 114, No. 42, 2010 11215 (25) Sivanesan, D.; Sumathi, I.; Welsh, W. J. Chem. Phys. Lett. 2003, 367, 351. (26) Hobza, P.; Sˇponer, J. J. Am. Chem. Soc. 2002, 124, 11802. (27) Jurecˇka, P.; Hobza, P. J. Am. Chem. Soc. 2003, 125, 15608. (28) Sˇponer, J.; Hobza, P. Chem. Phys. Lett. 1997, 267, 263. (29) Sˇponer, J.; Leszczynski, J.; Hobza, P. J. Mol. Struct.: THEOCHEM 2001, 573, 43. (30) Saeki, M.; Ishiuchi, S.; Sakai, M.; Fujii, M. J. Phys. Chem. A 2007, 111, 1001. (31) Even, U.; Jortner, J.; Noy, D.; Lavie, N. J. Chem. Phys. 2000, 112, 8068. (32) Yoshino, R.; Hashimoto, K.; Omi, T.; Ishiuchi, S.; Fujii, M. J. Phys. Chem. A 1998, 102, 6227. (33) Saeki, M.; Ishiuchi, S.; Sakai, M.; Fujii, M. J. Phys. Chem. A 2001, 105, 10045. (34) Sakai, M.; Daigoku, K.; Ishiuchi, S.; Saeki, M.; Hashimoto, K.; Fujii, M. J. Phys. Chem. A 2001, 105, 8651. (35) Lakshminarayan, C.; Knee, J. L. J. Phys. Chem. 1990, 94, 2637. (36) Knochenmuss, R.; Muin˜o, P. L.; Wickleder, C. J. Phys. Chem. 1996, 100, 11218. (37) Piaggio, P.; Rui, M.; Tubino, R.; Dellepiane, G. Spectrochim. Acta 1982, 38A, 913. (38) Tsui, A. P. In Physical Properties of Quasicrystals; Stadnik, Z. M., Ed.; Springer-Verlag: Berlin, Heidelberg, 1999; p 5. (39) Watanabe, A.; Yamaoka, Y.; Takada, K. Chem. Pharm. Bull. 1982, 30, 2958. (40) Lackinger, M.; Griessl, A.; Heckl, W. M.; Hietschold, M.; Flynn, G. W. Langmuir 2005, 21, 4984. (41) Kampschylte, L.; Lackinger, M.; Maier, A.-K.; Kishore, R. S. K.; Griessl, S.; Schmittel, M.; Heckl, W. M. J. Phys. Chem. B 2006, 110, 10829. (42) Li, Y.; Ma, Z.; Qi, G.; Yang, Y.; Zeng, Q.; Fan, X.; Wang, C.; Huang, W. J. Phys. Chem. C 2008, 112, 8649. (43) Frische, M. J. Gaussian 09, Revision A.02; Gaussian, Inc.: Wallingford, CT, 2009. (44) Zhao, Y.; Truhlar, D. G. Theor. Chem. Acc. 2008, 120, 215. (45) Boys, S. F.; Bernardi, F. Mol. Phys. 1970, 19, 553. (46) Sakota, K.; Hara, A.; Sekiya, H. Phys. Chem. Chem. Phys. 2004, 6, 32. (47) Davydov, A. S. Theory of Molecular Excitons; MsGraw-Hill: New York, 1962.
JP102849Q
