Na, K, Mg 2, Ca 2. potential-modulated fluorescence; Fig. 1 Chemical structure of dioc 2 (3) PMF. DCE W Li, Na, K, Mg 2, Ca 2 PMF.

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1 BUNSEKI KAGAKU Vol. 65, No. 2, pp The Japan Society for Analytical Chemistry 71 : dioc 2 (3) ,3'- dioc 2 (3) 1,2- DCE W Li, Na, K, Mg 2, Ca 2 dioc 2 (3) 4- DCE W potential-modulated fluorescence; PMF 5 8 1,2- DCE W PMF 9 10 PMF PMF 3,3'- 12 dioc 2 (3); Fig. 1 DCE W PMF osakai@kobe-u.ac.jp 1 : : Fig. 1 Chemical structure of dioc 2 (3) Li, Na, K, Mg 2, Ca dioc 2 (3) 98 Aldrich 4- BTPPATClPB BTPPA BTPPACl; Aldrich TClPB 5 1 : 1 DCE HPLC LiCl, NaCl, KCl, MgCl 2, CaCl 2 dioc 2 (3) TClPB

2 72 B U N S E K I K A G A K U Vol Fig. 2 Schematic representation of the four-electrode electrochemical cell RE1 and RE2, reference electrodes; CE1 and CE2, counter electrodes dioc 2 (3) TClPB DMSO DMSO 2 2 Fig. 2 LiCl NaCl, KCl, MgCl 2, CaCl 2 2 RE1 RE2 / 2 CE1 CE cm dioc 2 (3) PMF 1 dioc 2 (3) I 2 3 CV HA1010mM1S RE1 RE2 E Δ W O f f W f O E Δ W O f ΔE ref ΔE ref Fig. 1 ΔE ref V TMA E r 1/2, TMA V Δ W O f TMA ΔE ref Δ W O f TMA DCE W TMA V 13 C dl ACV 14 ACV CV 5 mv s 1 3, 6, 9 Hz 10 mv rms LI5640 Y Y Y Y Y AωC dl A ω 14 C dl 2 4 PMF PMF 8 cw DPSS Photop Suwtech DPBL- 9010F; 473 nm; 10 mw : 80 : Hz : 50 mv rms 5 mv s 1 AT100PM SPG120S 510 nm LI5640 PMF ΔF ΔF re ΔF img PMF 2 5 X X MoK α Å Bruker AXS APEX II Ultra SHELXS-2014 SHELXL F CV Fig. 3 LiCl

3 : dioc 2 (3) 73 Fig. 3 Cyclic voltammograms of the DCE W interface with (solid line) and without (dashed line) the addition of 30 μm dioc 2 (3) to the W phase Scan rate, 100 mv s 1. The inset shows the dependence of the positive currents at E 0.80 V, 0.83 V, and 0.87 V (shoulder peak) on the square root of the scan rate (v). Fig. 4 Potential dependence of C dl for the DCE W interface with (solid line) and without (dotted line) the addition of 30 μm dioc 2 (3) to the W phase base 0.1 V 0.9 V 30 μm dioc 2 (3) 0.8 V I pa 1 2 μa; cm 2 s 1 Randles-Sevcik 270 I pa v Fig. 3 Li 3 2 ACV Fig. 4 ACV C dl CV base C dl 0.4 V C dl dioc 2 (3) DCE W Δ W O f TClPB Fig. 5 Potential dependence of the PMF response for 30 μm dioc 2 (3) in W f 1 Hz; ac amplitude, 50 mv; wavelength, 510 nm; v, 5 mv s PMF Fig. 5 dioc 2 (3) PMF CV PMF 0.8 V PMF Fig V PMF ΔF re ΔF img PMF 90 TClPB TClPB π π Li

4 74 B U N S E K I K A G A K U Vol Fig. 6 Complex plane plot of ΔF img vs. ΔF re for 30 μm dioc 2 (3) in W Experimental conditions as in Fig. 5. Fig. 6 ΔF re ΔF img PMF Li Fig. 5 PMF 6 ΔF re Ψ DCE W dioc 2 (3) s p p Ψ 0 ΔF re ΔF re Ψ 5 Fig. 7 ΔF re X{sin 2 θ cos 2 (90 Ψ) (cos 2 ψ sin 2 θ 2sin 2 ψ cos 2 θ)sin 2 (90 Ψ)} 1 θ ψ X θ Fig. 8 E 0.4 V Δ W O f Fig. 7 Dependence of ΔF re for 30 μm dioc 2 (3) in W on the angle of polarization of the excitation beam (Ψ) The solid line was obtained by a least-squares curve fitting with Eq. (1). E, 0.8 V; f, 4 Hz; ac amplitude, 50 mv; wavelength, 510 nm; θ, 40 ; X, 17 (θ and X are the fitting parameters). dioc 2 (3) TClPB E 0.4 V Δ W O f 0 V ACV dioc 2 (3) TClPB E 0.6 V Li dioc 2 (3) TClPB 16 Fig. 9 dioc 2 (3) Fig. 9 TClPB Li Li TClPB bc 30 PMF dioc 2 (3) 40 dioc 2 (3) TClPB Fig. 9 Δ W O f 0 V TClPB dioc 2 (3) 1 Li

5 : dioc 2 (3) 75 Fig. 8 Proposed mechanism for the facilitated transfer of a cation (here, Li ) from W to the co-adsorption layer of dioc 2 (3) and TClPB being formed at the DCE W interface For further details, see the text. Fig. 9 Crystal structure (left) of the salt of dioc 2 (3) and TClPB and a possible structure (right) of their co-adsorption layer formed at the O W interface CV Li 1 cm dioc 2 (3) TClPB dioc 2 (3) TClPB 150 Å cm 2 1 cm Li dioc 2 (3) Li 3 5 Li Na, K, Cs, Mg 2, Ca 2, TMA Fig. 3 CV Li Mg 2 Ca 2 Na K dioc 2 (3) Ca 2 Fig. 10 Cs TMA dioc 2 (3) Cs Fig. 10 Table 1 i 17 Δ W O f i E pa Δ W O f i E pa dioc 2 (3) Table 1 Li Mg 2 Ca 2

6 76 B U N S E K I K A G A K U Vol Table 1 Anodic peak potentials (E pa ) and peak current (I pa ) for the facilitated transfer of cations by dioc 2 (3) (added at 30 μm to W) and standard potentials (Δ O W f i ) for their simple transfer at the DCE W interface Cation E pa a) /V Δ O W f i b) /V (Δ O W f i E pa )/V I pa c) /μa Li Na K Mg Ca a) Shown at the Δ O W f scale, i.e., being corrected for the reference-electrode potential, ΔE ref ( V); b) From ref. 17; c) Measured at the shoulder of the anodic wave. Note that the bulk concentration was 10 mm for Li, Na, and K and 5 mm for Mg 2 and Ca 2. ( ) Fig. 10 Cyclic voltammograms obtained for 5 mm CaCl 2 in W (upper) and 1 mm CsCl 10 mm LiCl in W (lower) with and without the addition of 30 μm dioc 2 (3) to the W phase Scan rate, 100 mv s 1. Table 1 I pa 10 mm 5 mm 4 dioc 2 (3) TClPB DCE W dioc 2 (3) TClPB dioc 2 (3) Mg 2 Ca 2 Mg 2 Ca 2 1) A. G. Volkov (Ed.) : Liquid Interfaces in Chemical, Biological, and Pharmaceutical Applications, Surfactant Science Series, Vol. 95, (2001), (Marcel Dekker, New York). 2) A. Waggoner : J. Membr. Biol., 27, 317 (1979). 3) J. Plášek, K. Sigler : J. Photochem. Photobiol. B, 33, 101 (1996). 4) L. M. Loew : Pure Appl. Chem., 68, 1405 (1996). 5) H. Nagatani, R. A. Iglesias, D. J. Fermín, P.-F. Brevet, H. H. Girault : J. Phys. Chem. B, 104, 6869 (2000). 6) H. Nagatani, D. J. Fermín, H. H. Girault : J. Phys. Chem. B, 105, 9463 (2001). 7) H. Nagatani, T. Sagara : Anal. Sci., 23, 1041 (2007). 8) T. Osakai, H. Yamada, H. Nagatani, T. Sagara : J. Phys. Chem. C, 111, 9480 (2007). 9) T. Osakai, J. Sawada, H. Nagatani : Anal. Bioanal. Chem., 395, 1055 (2009). 10) T. Osakai, T. Yoshimura, D. Kaneko, H. Nagatani, S.-H. Son, Y. Yamagishi, K. Yamada : Anal. Bioanal. Chem., 404, 785 (2012). 11) T. Yoshimura, H. Nagatani, T. Osakai : Anal. Bioanal. Chem., 406, 3407 (2014). 12) P. C. Laris, D. P. Bahr, R. R. Chaffee : Biochim. Biophys. Acta, 376, 415 (1975). 13) A. Sabela, V. Marecek, Z. Samec, R. Fuoco : Electrochim. Acta, 37, 231 (1992). 14) T. Osakai, T. Kakutani, M. Senda : Bull. Chem. Soc. Jpn., 57, 370 (1984). 15) H. Nagatani : Rev. Polarogr., 54, 123 (2008). 16) The crystallographic data is deposited in the Cambridge Crystallographic Data Centre with CCDC No This data can be obtained free of charge at request/cif. 17) M. Zhou, S. Gan, L. Zhong, X. Dong, J. Ulstrup, D. Han, L. Niu : Phys. Chem. Chem. Phys., 14, 3659 (2012).

7 : dioc 2 (3) 77 Facilitated Transfer of Alkali and Alkaline Earth-metal Ions to the Oil Water Interface Where the Fluorescent Dye dioc 2 (3) is Adsorbed Mika MORIGUCHI 1, Hirohisa NAGATANI 2, Kazuo EDA 1 and Toshiyuki OSAKAI 1 osakai@kobe-u.ac.jp 1 Department of Chemistry, Graduate School of Science, Kobe University, 1-1, Rokkodai, Nada-ku, Kobe-shi, Hyogo Faculty of Chemistry, Institute of Science and Engineering, Kanazawa University, Kakuma, Kanazawa-shi, Ishikawa (Received October 24, 2015; Accepted December 19, 2015) At the 1,2-dichloroethane (DCE) water (W) interface upon the addition of a monocationic membrane-potential-sensitive dye, 3,3'-diethyloxacarbocyanine {dioc 2 (3)}, an extraordinarily large voltammetric wave, was observed. This was probably due to a facilitated transfer of the supporting-electrolyte cation in W (i.e., Li, Na, K, Mg 2, Ca 2 ). In order to explain the mechanism, we also carried out a determination of the double-layer capacity of the interface by ac voltammetry and potential-modulated fluorescence (PMF) spectroscopy measurements. The results have suggested that monocationic dioc 2 (3) and the supporting-electrolyte anion in DCE {tetrakis(4-chlorophenyl)borate} are co-adsorbed (probably in multilayers) at the DCE W interface and, into the adsorption layer, the above cations of small sizes are intercalated, and thus transferred more easily. This facilitation effect is more significant for alkali-earth metal ions than for the alkali metal ions. A possible application has been suggested concerning the voltammetric or fluorescence determination of Mg 2 and/or Ca 2 (e.g., water hardness analysis). Keywords: membrane-potential-sensitive dye; liquid liquid interface; potential-modulated fluorescence spectroscopy; facilitated transfer.