dithiophosphorus derivatives have been a subject of intensive study due to having an important role in medicine , agricultural and industrial application fields in the last decades [ 1 - 15 ] . they have been utilized as additives in lubricant oils , solvent - extraction reagents for metals , and flotation agents for mineral ores , insecticides and pesticides [ 1 - 5 ] . while many dithiodiphosphonates and their derivatives such as thiophoshonyl disulfane have been synthesized by a ring opening reaction of lawesson reagent 's or its analogues and alcohols , zwitterionic dithiophosphonate and thiophoshonyl disulfane type compounds are rare . dithiophosphonates can be oxidized to bis(thiophoshonyl)disulfane by cu(ii ) ions or iodine   in this paper , we reported the synthesis of o-(1,3-bispiperidino-2-propyl)-4-methoxy phenyldithiophosphonate and the kinetic behavior of the transport process as a function of concentration , temperature , stirring rate and solvents was also investigated . the compound 1 the reaction of 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide with 1,3-bispiperidino-2-propanol gave rise to the formation 1 which was previously synthesized ( scheme 1 ) . the compound was obtained in high yield and was characterized by elemental analysis , ir , h - nmr and p - nmr spectroscopies . although dithiophosphonates were usually obtained as liquid product , the compound 1 was obtained as solid product due to zwitterionic character in which the h atom of the initially formed p - sh group transferred to the piperidino group . the ir spectra of 1 showed its characteristic bands at 671 cmfor n(ps)asym and 548 cmfor n(ps)sym stretchings . the h - nmr spectra of 1 indicated that the phenyl protons displayed doublet at 8.13 - 8.08 ppm ( jph = 14.19 hz , jhh = 8.81 hz ) and 6.90 - 6.87 ppm ( jph = 2.45 hz , jh , h = 8.81 hz ) , respectively . however , the proton on n atom was not observed in the spectra of h nmr . the p - nmr spectra of 1 displayed a quartet at 112.73 ppm because of the coupling with hydrogen nuclei and the presence of two isomer in solution(see scheme 1 ) . in our previous report , the transport of cu(ii ) ions from aqueous phase was carried out by using the compound 1 as the carrier . in this work , the transport of mercury(ii ) ion by the zwitterionic dithiophosphonate 1 in the liquid membrane was studied and the kinetic behavior of the transport process as a function of concentration , temperature , stirring rate and solvents was investigated . the mechanism of the ion pair mediated transport ( co - transport ) is given in figure 1 . l represents the carrier 1 . at the interface between donor and membrane , metal picrate ion pair forms complex with ligand , then the [ lm]piccomplex diffuses through the membrane . at the interface between membrane and acceptor , the carrier ion pairs are decomplexed and mpicis liberated into the acceptor phase . finally , the ligand carrier diffuses back across the membrane aqueous boundary layers . the variation of the metal picrate concentration with time was directly measured in both the donor ( cd ) and acceptor ( ca ) phases . in the experiments , the variation of picrate ion concentration with time was directly measured in both donor ( cd ) and acceptor phases ( ca ) . the corresponding change of picrate ion concentration in the membrane phase was determined from the material balance between the phases . mechanism of the ion pair mediated transport ( co - transport ) through liquid membrane m : metal , pic : picrate salt , l : ligand , [ l - m]pic : ion pair . for practical reasons , the dimensionless reduced concentrations were used:(1 ) where cd0 is the initial mercury(ii ) ion concentration in the donor phase , while cd , cm and ca represents the mercury(ii ) ion concentration in donor , membrane and acceptor phases , respectively . the material balance with respect to the reduced concentrations can be expressed as rd + rm + ra = 1 . from this expression , the kinetic behavior of the consecutive irreversible first order reactions can be described as follows;(2 ) where k1 and k2 are the apparent membrane entrance and exit rate constants , respectively . the kinetic scheme for consecutive reaction systems and the kinetic parameters of k1 and k2 from the obtained data were calculated by fitting equations as described in the previous studies [ 17 - 24 ] . the variation of the reduced concentration of mercury(ii ) ion through the liquid membrane with 1x10 m of carrier 1 in chcl3 at 300 rpm and 25c is presented in figure 2 . the observed experimental results reveal that rd decreases exponentially with time , accompanied by a simultaneous increase of ra , whereas rm presents a maximum at intermediate times . the transport experiments were carried out at three different initial carrier 1 concentrations 1x10 , 1  10 , and 1  10 m in chcl3 at 298 k and 300 rpm . the obtained kinetic parameters for the effect of concentration of carrier 1 are presented in table 1 . it was found that the initial carrier concentration influences the kinetic constants , as well as flux values and the results are in full agreement with previously obtained results [ 17 - 24 ] . it can be seen that both kinetic constants k1 and k2 or fluxes are dependent on the carrier concentration and increases steadily with the initial carrier concentration as shown in figure 3 . in addition , a blank experiment was performed with no present carrier in the membrane . there was no evidence of the movement of the mercury(ii ) ions through the liquid membrane in the blank experiment . when the carrier was utilized , the transport of mercury(ii ) ions through the liquid membrane was performed . the kinetic parameters for mercury(ii ) ions at different carrier 1 concentrations in chcl3 ( 298 k and 300 rpm ) concentration dependence of k1 and k2 for transport of mercury(ii ) with 1 ( 298 k and 300 rpm in chcl3 ) . effect of temperature on transport of mercury(ii ) ions the effect of temperature on the transport of mercury(ii ) ions through the liquid membrane containing 1  10 m of carrier 1 in chcl3 was examined at 293 , 298 , 303 , and 308 k ( 300 rpm ) . it is quite obvious that k1 and k2 increases with an increase in the temperature . the kinetic parameters of mercury(ii ) transport using carrier 1 at different temperatures ( stirring rate is 300 rpm ; solvent is chcl3 ) the activation energy was calculated from plot of the maximum membrane exit flux ( ja ) versus ( 1/t ) at 300 rpm(equation 3 ) , as presented in figure 4.(3 ) arrhenius plots for transport of mercury(ii ) in liquid membrane . the activation energy value for carrier 1 in the liquid membrane was found to be 1.36 kcal / mol by using the equation 3 . as known , activation energy values are quite low for diffusion - controlled processes , whose rate constants are strongly affected by temperature . it was pointed out that the activation energies of diffusion - controlled processes are lower than 10 kcal / mol . the calculated activation energy for carrier 1 shows that the transport of mercury(ii ) ion is diffusion - controlled processes . to achieve effective mercury(ii ) transport , it is necessary to explore the effect of stirring speed on the transport process . in the present investigation , the stirring rate of the membrane phase was carried out at three different stirring rate , 200 , 300 , and 400 rpm at 298 k when the carrier 1 concentration was 1  10 m in chcl3 . the results are given in table 3 and indicate that the stirring rate affects the transport rate of mercury(ii ) through the liquid membrane . according to these results , the flux increases with increasing stirring rate due to decrease of the thickness of the diffusion boundary layers at both interfaces of the membrane . the kinetic parameters of mercury(ii ) transport using carrier 1 at different stirring rates ( t = 298 k ; solvent is chcl3 ) the present work was to investigate the physicochemical approach to co - transport of mercury(ii ) transport through a liquid membrane containing carrier 1 . therefore , the effect of solvents on the transport process was studied under the same conditions , and the results obtained with ch2cl2 and ccl4 are presented in table 4 , along with analogous results for chcl3 . it has been observed that the membrane entrance and exit rate constants are found to vary in the order ch2cl2 > chcl3 > ccl4 , and the variation of ra values is illustrated in figure 5 . this shows that the ra values are strongly affected by the membrane solvent system , and the higher transport efficiency was observed with ch2cl2 solvent . the efficiency of ch2cl2 with respect to the ra values was higher than of chcl3 and ccl4 , because their viscosity values were in the reverse order . the kinetic parameters for mercury(ii ) transport using carrier 1 when different solvents are used ( 298 k and 300 rpm ) time variation of reduced concentrations of mercury(ii ) in the acceptor phase during co - transport through liquid membrane using of carrrier 1 in different solvents at a stirring rate of 300 rpm . these observations suggest that viscosity is playing a major role in ion transport as well as the polarity . thus , we have shown that the nature of the membrane solvent is one of the main factors in establishing transport efficiency . physicochemical characteristic of solvents used 0 : dielectric constant ( 20c ) ; nd : refractive index ( 20c ) ;  : dipole moment ( d ) ;  : viscosity ( cp ) ; vm : molar volume ( m ) . in our previous report , the transport of cu(ii ) ions from aqueous phase was carried out by using the compound 1 as the carrier . in this work , the transport of mercury(ii ) ion by the zwitterionic dithiophosphonate 1 in the liquid membrane was studied and the kinetic behavior of the transport process as a function of concentration , temperature , stirring rate and solvents was investigated . the mechanism of the ion pair mediated transport ( co - transport ) is given in figure 1 . l represents the carrier 1 . at the interface between donor and membrane , metal picrate ion pair forms complex with ligand , then the [ lm]piccomplex diffuses through the membrane . at the interface between membrane and acceptor , the carrier ion pairs are decomplexed and mpicis liberated into the acceptor phase . finally , the ligand carrier diffuses back across the membrane aqueous boundary layers . the variation of the metal picrate concentration with time was directly measured in both the donor ( cd ) and acceptor ( ca ) phases . in the experiments , the variation of picrate ion concentration with time was directly measured in both donor ( cd ) and acceptor phases ( ca ) . the corresponding change of picrate ion concentration in the membrane phase was determined from the material balance between the phases . mechanism of the ion pair mediated transport ( co - transport ) through liquid membrane m : metal , pic : picrate salt , l : ligand , [ l - m]pic : ion pair . for practical reasons , the dimensionless reduced concentrations were used:(1 ) where cd0 is the initial mercury(ii ) ion concentration in the donor phase , while cd , cm and ca represents the mercury(ii ) ion concentration in donor , membrane and acceptor phases , respectively . the material balance with respect to the reduced concentrations can be expressed as rd + rm + ra = 1 . from this expression , the kinetic behavior of the consecutive irreversible first order reactions can be described as follows;(2 ) where k1 and k2 are the apparent membrane entrance and exit rate constants , respectively . the kinetic scheme for consecutive reaction systems and the kinetic parameters of k1 and k2 from the obtained data were calculated by fitting equations as described in the previous studies [ 17 - 24 ] . the variation of the reduced concentration of mercury(ii ) ion through the liquid membrane with 1x10 m of carrier 1 in chcl3 at 300 rpm and 25c is presented in figure 2 . the observed experimental results reveal that rd decreases exponentially with time , accompanied by a simultaneous increase of ra , whereas rm presents a maximum at intermediate times . the transport experiments were carried out at three different initial carrier 1 concentrations 1x10 , 1  10 , and 1  10 m in chcl3 at 298 k and 300 rpm . the obtained kinetic parameters for the effect of concentration of carrier 1 are presented in table 1 . it was found that the initial carrier concentration influences the kinetic constants , as well as flux values and the results are in full agreement with previously obtained results [ 17 - 24 ] . it can be seen that both kinetic constants k1 and k2 or fluxes are dependent on the carrier concentration and increases steadily with the initial carrier concentration as shown in figure 3 . in addition , a blank experiment was performed with no present carrier in the membrane . there was no evidence of the movement of the mercury(ii ) ions through the liquid membrane in the blank experiment . when the carrier was utilized , the transport of mercury(ii ) ions through the liquid membrane was performed . the kinetic parameters for mercury(ii ) ions at different carrier 1 concentrations in chcl3 ( 298 k and 300 rpm ) concentration dependence of k1 and k2 for transport of mercury(ii ) with 1 ( 298 k and 300 rpm in chcl3 ) . effect of temperature on transport of mercury(ii ) ions the effect of temperature on the transport of mercury(ii ) ions through the liquid membrane containing 1  10 m of carrier 1 in chcl3 was examined at 293 , 298 , 303 , and 308 k ( 300 rpm ) . it is quite obvious that k1 and k2 increases with an increase in the temperature . the kinetic parameters of mercury(ii ) transport using carrier 1 at different temperatures ( stirring rate is 300 rpm ; solvent is chcl3 ) the activation energy was calculated from plot of the maximum membrane exit flux ( ja ) versus ( 1/t ) at 300 rpm(equation 3 ) , as presented in figure 4.(3 ) arrhenius plots for transport of mercury(ii ) in liquid membrane . the activation energy value for carrier 1 in the liquid membrane was found to be 1.36 kcal / mol by using the equation 3 . as known , activation energy values are quite low for diffusion - controlled processes , whose rate constants are strongly affected by temperature . it was pointed out that the activation energies of diffusion - controlled processes are lower than 10 kcal / mol . the calculated activation energy for carrier 1 shows that the transport of mercury(ii ) ion is diffusion - controlled processes . to achieve effective mercury(ii ) transport , it is necessary to explore the effect of stirring speed on the transport process . in the present investigation , the stirring rate of the membrane phase was carried out at three different stirring rate , 200 , 300 , and 400 rpm at 298 k when the carrier 1 concentration was 1  10 m in chcl3 . the results are given in table 3 and indicate that the stirring rate affects the transport rate of mercury(ii ) through the liquid membrane . according to these results , the flux increases with increasing stirring rate due to decrease of the thickness of the diffusion boundary layers at both interfaces of the membrane . the kinetic parameters of mercury(ii ) transport using carrier 1 at different stirring rates ( t = 298 k ; solvent is chcl3 ) the present work was to investigate the physicochemical approach to co - transport of mercury(ii ) transport through a liquid membrane containing carrier 1 . therefore , the effect of solvents on the transport process was studied under the same conditions , and the results obtained with ch2cl2 and ccl4 are presented in table 4 , along with analogous results for chcl3 . it has been observed that the membrane entrance and exit rate constants are found to vary in the order ch2cl2 > chcl3 > ccl4 , and the variation of ra values is illustrated in figure 5 . this shows that the ra values are strongly affected by the membrane solvent system , and the higher transport efficiency was observed with ch2cl2 solvent . the efficiency of ch2cl2 with respect to the ra values was higher than of chcl3 and ccl4 , because their viscosity values were in the reverse order . the kinetic parameters for mercury(ii ) transport using carrier 1 when different solvents are used ( 298 k and 300 rpm ) time variation of reduced concentrations of mercury(ii ) in the acceptor phase during co - transport through liquid membrane using of carrrier 1 in different solvents at a stirring rate of 300 rpm . these observations suggest that viscosity is playing a major role in ion transport as well as the polarity . thus , we have shown that the nature of the membrane solvent is one of the main factors in establishing transport efficiency . physicochemical characteristic of solvents used 0 : dielectric constant ( 20c ) ; nd : refractive index ( 20c ) ;  : dipole moment ( d ) ;  : viscosity ( cp ) ; vm : molar volume ( m ) . a kinetic study of mercury(ii ) transport through a membrane assisted by o-(1,3-bispiperidino-2-propyl)-4-methoxy phenyldithiophosphonate was performed . the kinetic behavior of the transport process as a function of concentration , temperature , stirring rate and solvents was investigated . it can be concluded that dithiophosphorus derivatives can be provided a general and straightforward route to remove toxic metals ions such as mercury(ii ) ion from water or other solution . h - nmr spectra were obtained in chloroform with a bruker - dpx 400 ftnmr spectrometer . ir spectra was recorded on a mattson 1000 ftir spectrometer using kbr pellets in the range of 4000 - 400 cm . the chemical reagents used in these experiments were mercury(ii ) nitrate , dichloromethane , chloroform , carbon tetracholoride and picric acid obtained from merck . mercury(ii ) picrate solution was prepared by the addition of a 1  10 m mercury(ii ) nitrate to a 2.5  10 m aqueous picric acid solution and shaken at 25c for 1 hour . mercury(ii ) ion transport experiments were conducted using a thermostated ( grand mark , model w14 , grants instruments , cambridge , england ) apparatus . transport experiments were carried out in a u - type cell ( figure 6 ) . an organic solution ( 20 ml ) containing the carrier 1 was placed in the bottom of the cell and two portions of aqueous donor and acceptor solutions ( 10 ml ) were carefully added on top of them . the organic phase was stirred at variable speeds magnetically ( chiltern mark , model hs 31 ) . the initial phases consisted of the donor phase , an aqueous mercury(ii ) picrate ( 2.5  10 m ) solution , while the membrane phase was made up by dissolving carrier 1 ( ccarrier = 10 m ) in the organic phase . samples were taken from both water phases ( acceptor and donor phases ) at various intervals of time and the picrate ion concentration was analyzed by a spectrophotometric method . bulk liquid membrane apparatus for transport of mercury(ii ) ions ; d , donor phase ; a , acceptor phase ; m , membrane phase . 2,4-bis ( methoxyphenyl-1,3,2,4- dithiadiphosphetane-2,4-disulfide ( lawesson 's reagent ) ( 0.89 g , 2.21 mmol ) was reacted with 1,3-bispiperidino-2-propanol ( 1 g , 4.42 mmol ) in benzene ( 5 ml ) . . elemental analysis calc . for c20h33n2o2ps2 : c , 56.04 ; h , 7.76 ; n , 6.53 ; s , 14.96 . found : c , 55.80 ; h , 7.52 ; n , 6.0 ; s , 14.58 . ir ( cm ) : 1035 n(p - o - c ) , 671 n(ps ) , 548 n(ps ) . h - nmr ( cdcl3 ) , d : 8.13 - 8.08 ( dd , 2 h , jph = 14.19 hz , jhh = 8.81 hz ) , 6.90 - 6.87 ( dd , 2 h , jph = 2.45 hz , jhh = 8.81 hz ) , 5.36 - 5.30 ( m , 1 h , och ) , 3.81 ( s , 3 h , och3 ) , 3.03 - 2.99 ( m , 8 h , orto protons to n on the piperidino ring ) , 2.91 - 2.86 ( m , 4 h , bridge methylene h ) , 1.82 - 1.77 ( m , 8 h , meta protons to n on the piperidino ring ) , 1.56 - 1.53 ( m , 4 h , para protons to n on the piperidino ring ) . p - nmr ( cdcl3 ) , d : 112.73 ( q , due to the coupling with hydrogen nuclei and the presence of two isomer in solution)(see scheme 1 ) . h - nmr spectra were obtained in chloroform with a bruker - dpx 400 ftnmr spectrometer . ir spectra was recorded on a mattson 1000 ftir spectrometer using kbr pellets in the range of 4000 - 400 cm . the chemical reagents used in these experiments were mercury(ii ) nitrate , dichloromethane , chloroform , carbon tetracholoride and picric acid obtained from merck . mercury(ii ) picrate solution was prepared by the addition of a 1  10 m mercury(ii ) nitrate to a 2.5  10 m aqueous picric acid solution and shaken at 25c for 1 hour . mercury(ii ) ion transport experiments were conducted using a thermostated ( grand mark , model w14 , grants instruments , cambridge , england ) apparatus . transport experiments were carried out in a u - type cell ( figure 6 ) . an organic solution ( 20 ml ) containing the carrier 1 was placed in the bottom of the cell and two portions of aqueous donor and acceptor solutions ( 10 ml ) were carefully added on top of them . the organic phase was stirred at variable speeds magnetically ( chiltern mark , model hs 31 ) . the initial phases consisted of the donor phase , an aqueous mercury(ii ) picrate ( 2.5  10 m ) solution , while the membrane phase was made up by dissolving carrier 1 ( ccarrier = 10 m ) in the organic phase . samples were taken from both water phases ( acceptor and donor phases ) at various intervals of time and the picrate ion concentration was analyzed by a spectrophotometric method . bulk liquid membrane apparatus for transport of mercury(ii ) ions ; d , donor phase ; a , acceptor phase ; m , membrane phase . 2,4-bis ( methoxyphenyl-1,3,2,4- dithiadiphosphetane-2,4-disulfide ( lawesson 's reagent ) ( 0.89 g , 2.21 mmol ) was reacted with 1,3-bispiperidino-2-propanol ( 1 g , 4.42 mmol ) in benzene ( 5 ml ) . the yield is 1.35 g ( 72% ) and mp:178 - 180c . elemental analysis calc . for c20h33n2o2ps2 : c , 56.04 ; h , 7.76 ; n , 6.53 ; s , 14.96 . found : c , 55.80 ; h , 7.52 ; n , 6.0 ; s , 14.58 . ir ( cm ) : 1035 n(p - o - c ) , 671 n(ps ) , 548 n(ps ) . h - nmr ( cdcl3 ) , d : 8.13 - 8.08 ( dd , 2 h , jph = 14.19 hz , jhh = 8.81 hz ) , 6.90 - 6.87 ( dd , 2 h , jph = 2.45 hz , jhh = 8.81 hz ) , 5.36 - 5.30 ( m , 1 h , och ) , 3.81 ( s , 3 h , och3 ) , 3.03 - 2.99 ( m , 8 h , orto protons to n on the piperidino ring ) , 2.91 - 2.86 ( m , 4 h , bridge methylene h ) , 1.82 - 1.77 ( m , 8 h , meta protons to n on the piperidino ring ) , 1.56 - 1.53 ( m , 4 h , para protons to n on the piperidino ring ) . p - nmr ( cdcl3 ) , d : 112.73 ( q , due to the coupling with hydrogen nuclei and the presence of two isomer in solution)(see scheme 1 ) . mk has coordinated the study and characterization of the compound 1 . na carried out the synthesis of the compound 1 . hka and ak carried out the kinetic studies and participated in the design of the study . this work was supported by tubitak grant no : tbag - hd/123 ( 106t034 ) .
backgrounda new organodithiophosphorus derivative , namely o-(1,3-bispiperidino-2-propyl)-4-methoxy phenyldithiophosphonate , was synthesized and then the kinetic behavior of the transport process as a function of concentration , temperature , stirring rate and solvents was investigated.resultsthe compound 1 was characterized by elemental analysis , ir , 1h and 31p nmr spectroscopies . 
 the transport of mercury(ii ) ion by a zwitterionic dithiophosphonate 1 in the liquid membrane was studied and the kinetic behavior of the transport process as a function of concentration , temperature , stirring rate and solvents was investigated . 
 the compound 1 is expected to serve as a model liquid membrane transport with mercury(ii ) ions.conclusiona kinetic study of mercury(ii ) transport through a membrane assisted by o-(1,3-bispiperidino-2-propyl)-4-methoxy phenyldithiophosphonate was performed . 
 it can be concluded that the compound 1 can be provided a general and straightforward route to remove toxic metals ions such as mercury(ii ) ion from water or other solution .