Patent Application: US-201113820574-A

Abstract:
hyperhalogens , a new class of highly electronegative species , are now invented . a hyperhalogen is a superhalogen - containing composition in which the electron affinity of the hyperhalogen is even larger than that of the superhalogens they are composed of . novel production methods are provided in which highly electronegative species are produced by surrounding a central metal atom by superhalogen moieties .

Description:
inventive compositions with high ea , relative to superhalogens , are provided . the invention is based on a discovery , by the present inventors , of a new class of stable ternary nanoclusters with superhalogen units as building blocks , whose electron affinities can be larger than even the superhalogens that make up these clusters . these new nanoclusters , called hyperhalogens , can be better oxidizing agents than the traditional superhalogens . the hyperhalogen clusters , due their high electron - affinity , will exist as negatively charged ions and thus are useable as building blocks to synthesize inventive super - oxidizing agents . depending on the nature of central metal atom / core of the hyperhalogen , these species can carry a sizeable magnetic moment and can be novel magnetic materials with hyperhalogen building blocks . examples of uses of negatively charged molecules are , e . g ., as air purifiers , oxidizers , improving hygiene , etc . in addition , there is evidence that negatively charged molecules promote release of serotonin in the blood and hence can help treat depression . examples of uses for the invention include , e . g ., disinfectants , air cleaners , mood enhancers , etc . in this example , au was the central metal atom and bo 2 was the superhalogen building block . when the oxygen atoms in the auo 2 cluster were sequentially replaced with bo 2 units , the ea of the resulting cluster increased continuously and for au ( bo 2 ) 2 cluster , the ea was as high as 5 . 54 ev . this ea is much larger than the ea of bo 2 ( 4 . 32 ev ), the superhalogen building unit of this species . fig5 illustrates the increasing ea ( electron binding energy ) with sequential replacement of the oxygen atoms with bo 2 units , finally resulting in the hyperhalogen . in this example , a hyperhalogen was constructed by replacing the central metal atom with a multi - metal core . the au atom was replaced with au 3 cluster in auo ( bo 2 ) species . the resulting au 3 o ( bo 2 ) has an ea larger than the bo 2 unit , thus making it a hyperhalogen . the results of theoretical calculations were validated by carrying out experimental studies . thus , based on this discovery , a whole new series of highly electronegative species can be synthesized by manipulating the central metal core as well as the superhalogen building blocks . a cu - borate [ cu (( bo 2 ) 2 ] was experimentally observed in gas - phase . in this example , we show that a new class of highly electronegative species can be synthesized if the peripheral halogen atoms are replaced by superhalogen moieties . we name this new class of electronegative species “ hyperhalogens ” because their electron affinities can even be larger than those of their superhalogen building blocks and hence can serve as ingredients in the synthesis of new superoxidizing agents . using density functional theory ( dft ) and photoelectron spectroscopy ( pes ) experiments we demonstrate this by concentrating on an au atom as well as an au cluster decorated with bo 2 superhalogens . bo 2 molecule , like mno 4 , has a large electron affinity of 432 ev [ 19 , 21 ], while its anionic counterpart , bo 2 − being iso - electronic with co 2 , is a very stable anion . it has been shown recently that the ea of a xf n ( x = cu — au , n = 1 - 6 ) cluster increases as the central coinage metal atom , is decorated successively with f atoms [ 22 , 23 ]. this happens as the extra electron is delocalized over several halogen atoms . we questioned whether the electron affinity would increase even further if the metal atom is decorated with superhalogen molecules instead . note that in this case the extra electron will be delocalized over superhalogen moieties . we considered what would happen if one were to replace some but not all of the halogens atoms with superhalogen molecules ; whether the electron affinity would lie in between the two ( for example , whether the electron affinity of au ( bo 2 ) 2 would be much larger than that of auo 2 ; similarly , whether the electron affinity of auo ( bo 2 ) would be in between that of auo 2 and au ( bo 2 ) 2 ). from our dft based calculations ( see the table in fig6 ) we found that the electron affinity of au ( bo 2 ) 2 is 5 . 54 ev which is 1 . 6 times larger than that of auo 2 [ 24 ]. on the other hand , the electron affinity of auo ( bo 2 ) is 4 . 21 ev which lies between that of auo 2 and au ( bo 2 ) 2 . these results are validated by our photoelectron spectroscopy measurements . the fact that the electron affinities of superhalogens can be further enhanced by modifying the building blocks provides a new method for designing highly electronegative species . by suitably choosing the composition of these hyperhalogens and corresponding cations , new materials can be designed and synthesized with unique properties . in the following we provide details of our computational and experimental results . ( a ) auo , auo 2 vs au ( bo 2 ), au ( bo 2 ) 2 , and auo ( bo 2 ) clusters the electron affinity and vertical detachment energies of auo and auo 2 have been reported earlier by both experimental and theoretical groups [ 24 - 27 ]. according to the most recent work , auo has an ea of 2 . 378 ev and the vde of auo − is also measured as 2 . 378 ev , while the theoretical calculations carried out at ccsd ( t ) level gave a vde of 2 . 312 ev [ 24 ]. we use these reported values for comparison with the corresponding values for au ( bo 2 ) n ( n = 1 - 2 ) and auo ( bo 2 ) clusters in our table ( fig6 ). first we discuss the electron affinity of auo and au ( bo 2 ). as the o atom is replaced by bo 2 in auo , the electron affinity of the resultant au ( bo 2 ) cluster increases to 2 . 8 ev ( see fig6 ). similarly , a comparison of the vde of ( auo ) − and [ au ( bo 2 )] − clusters show that the replacement of o with bo 2 results in an increase of 0 . 6 ev , from 2 . 378 ev to 3 . 0 ev . this is in spite of the fact that au ( bo 2 ) is a closed shell system while auo is an open shell system . even though neither auo nor au ( bo 2 ) is a superhalogen , it is important to note that replacing an electronegative atom , o , by a superhalogen , bo 2 , leads to a significant increase in electron affinity . this will be shown , below , to play a major role . we next consider auo 2 and au ( bo 2 ) 2 clusters . the latter is formed by replacing two o atoms with two bo 2 superhalogen moieties . the electron affinity of auo 2 was reported to be 3 . 40 ev which is larger than that of auo [ 24 ]. strikingly , the electron affinity of au ( bo 2 ) 2 is 5 . 7 ev which is substantially larger than that of auo 2 and au ( bo 2 ) ( see fig6 ). similarly , the vde of [ au ( bo 2 ) 2 ] − is 5 . 9 ev , while the vde of [ auo 2 ] − was reported as 3 . 40 ev . given the fact that bo 2 behaves as a monovalent species , while o is divalent , one may wonder if the comparison of the ea between auo 2 and au ( bo 2 ) 2 is meaningful . in order to address this issue and have a better comparison , we have considered monovalent species , namely halogens as the ligands . we calculated the ea values of aux 2 , ( x = f , cl , br , and i ) and compared them with that of au ( bo 2 ) 2 cluster . note that in both aux 2 and au ( bo 2 ) 2 , the au atom is in the same oxidation state . our calculated ea values of auf 2 , aucl 2 , aubr 2 , and aui 2 molecules are 4 . 84 ev , 4 . 63 ev , 4 . 46 ev , and 4 . 38 ev , respectively , which are in good agreement with previous experimental and theoretical studies [ 28 , 29 ]. it is observed that the ea values of aux 2 molecules are significantly smaller than that of the corresponding theoretical ea ( 5 . 54 ev ) of au ( bo 2 ) 2 cluster . we , therefore , term au ( bo 2 ) 2 as a hyperhalogen since its electron affinity is significantly increased by replacing the peripheral o atoms ( in auo 2 ) or halogen atoms ( in aux 2 ) with the superhalogen moiety , bo 2 . regarding the properties of the au ( bo 2 ) 2 hyperhalogen we first discuss the ground state geometries of its neutral and anionic configurations given in fig1 . we found two energetically degenerate structural isomers having cis and trans form for both the neutral and anionic species . note that in these two isomers the geometry of bo 2 moieties remains unaltered from its isolated state [ 19 , 21 ]. the neutral au ( bo 2 ) 2 cluster is an open - shell system , with a doublet ( 2s + 1 = 2 ) spin multiplicity . the natural bond orbital ( nbo ) charge analysis of the neutral cluster clearly showed that there is a charge transfer from the au atom to both bo 2 moieties , resulting in a charge of + 0 . 92e on the au atom , and a charge of − 0 . 46e on each of the bo 2 moieties . however , each bo 2 moiety requires one electron to be stabilized . thus , the neutral au ( bo 2 ) 2 cluster lacks one electron , similar to that of a halogen atom . the [ au ( bo 2 ) 2 ] − cluster is a closed - shell system with a large homo - lumo gap of 5 . 68 ev . the unusually large homo - lumo gap , electronic shell closure , and the large binding energy of the extra electron ( ebe or vde ) makes the [ au ( bo 2 ) 2 ] − cluster a very stable anion , ideal for making a salt . the nbo charge analysis shows that the extra electron is delocalized over the entire cluster , thereby stabilizing both the bo 2 moieties as well as the entire [ au ( bo 2 ) 2 ] − cluster . the vde &# 39 ; s of both isomers of [ au ( bo 2 ) 2 ] − cluster are calculated to be 5 . 66 ev and 5 . 62 ev , respectively . the fes of the [ au ( bo 2 ) 2 ] − cluster obtained from our experiments is shown in fig2 and compared with that of [ au ( bo 2 )] − and [ auo ( bo 2 )] − . the experimental electron affinity of [( aubo 2 ) 2 ] is estimated to be 5 . 7 ev , while the measured vde is 5 . 9 ev . the calculated vdes for both the isomers are in good agreement with the measured value ( 5 . 9 ev ± 0 . 1 ev ) in the table ( fig6 ). therefore , one cannot rule out the possibility that both these isomers could be present in the cluster beam . the enhanced stability of [ au ( bo 2 ) 2 ] − is thus reflected in the pes as large vde and ea values . this is further confirmed by studying the thermodynamic stability of the au ( bo 2 ) 2 cluster , namely by calculating the energy required to fragment the cluster into smaller stable clusters . the binding energy of au ( bo 2 ) 2 measured with respect to au ( bo 2 ) and bo 2 is 2 . 09 ev . the binding energy of [ au ( bo 2 ) 2 ] − measured with respect to au ( bo 2 ) and bo 2 − is 3 . 31 ev and with respect to [ au ( bo 2 )] − and bo 2 is 4 . 57 ev . thus , the hyperhalogen au ( bo 2 ) 2 not only possesses anomalously large electron affinity , but also has a very stable anion . because au can exist in an oxidation state of + 3 , one would expect au ( bo 2 ) 4 to also have larger electron affinity than , say auf 4 . to examine this , we computed the equilibrium geometries of neutral and anionic au ( bo 2 ) 4 . two nearly degenerate structures were found for the anionic au ( bo 2 ) 4 ; one having the shape of a crossed structure with bent aims and the other in the form where o — au — o is bonded to a b 4 o 6 structure . the vertical and adiabatic detachment energies of the former isomer are , respectively , 7 . 13 ev and 7 . 10 ev . note that the electron affinity of auf 4 is calculated to be 6 . 84 ev [ 23 ]. it is to be noted here that the crossed structure with bent arms is similar to the previously reported [ 30 ] au ( n 3 ) 4 − unit in ammonium tetraazidoaurates ( iii ). we now address the structure and electron affinity of the auo ( bo 2 ) cluster which is formed when one of the o atoms of auo 2 is replaced by a bo 2 molecule . here the o atom can either bind to au forming auo ( bo 2 ) or to bo 2 forming au ( bo 3 ) cluster . the ground state geometries of the neutral and anionic auo ( bo 2 ) cluster are shown in fig3 ( a ) and ( a ′), respectively . in both cases , the structure of the bo 2 moiety again remains intact and the o atom binds to au . however , the b — o — au angle increased from 128 ° in the anion to 160 ° in the neutral . the neutral auo ( bo 2 ) cluster prefers a triplet ( 2s + 1 = 3 ) spin multiplicity , while the anion is a doublet ( 2s + 1 = 2 ). the singlet state ( 2s + 1 = 1 ) of the neutral auo ( bo 2 ) cluster is 1 . 34 ev higher in energy than the triplet state . the pes of the [ auo ( bo 2 )] − cluster is given in fig2 . the calculated electron affinity of the auo ( bo 2 ) cluster is 4 . 21 ev which agrees well with the experimental value of 4 . 0 ev . in addition , note that the first peak in the pes spectra of [ auo ( bo 2 )] − is broad . this is due to the structural relaxation of the resultant neutral cluster as the extra electron is removed ( see fig3 ( a , a ′)). the calculated vde , which corresponds to the transition from the anionic doublet to neutral triplet state , is 4 . 42 ev . note that this transition originates from the detachment of a β ( spin - down ) electron from the anionic doublet , thereby resulting in a triplet spin state . our calculated vde is in excellent agreement with the measured vde of 4 . 4 ev . the next higher energy peak in the pes ( in the range of 5 - 5 . 4 ev ) corresponds to the electron detachment from a spin - down electron as well . we also note that the peak at ˜ 5 . 6 ev in fig2 can be explained as originating from the transition from the spin doublet ground state of the anion to the spin singlet excited state of the neutral . the calculated value for this transition is 5 . 98 ev . the 4 th energy peak in the energy range of 6 - 7 ev is a combination of transitions to excited state neutral triplet and singlet states . the electron affinity of the auo ( bo 2 ) cluster is in between that of the corresponding values of auo 2 and au ( bo 2 ) 2 clusters . we investigated about creation of a hyperhalogen by manipulating the central metal core as we have shown we can do by replacing the peripheral halogen atoms by superhalogen moieties . this is accomplished by comparing the structure and properties of auo ( bo 2 ) and au 3 o ( bo 2 ) clusters . in fig3 ( b 1 , b 2 , b 1 ′, b 2 ′) we show the geometries of the ground state and higher energy isomer of the neutral and anionic au 3 o ( bo 2 ) clusters . in the neutral au 3 o ( bo 2 ) cluster , the o atom inserts into the au 3 cluster , thereby forming an au 2 oau segment , which in turn binds weakly to both the oxygen atoms of bo 2 moiety ( see fig3 ( b 1 )). in the higher energy isomer ( fig3 ( b 2 ), δe = 0 . 67 ev ) a chain of au — au — 0 bonds is formed with o bonding to the third au atom , which in turn is bonded to the bo 2 moiety . interestingly , the spin multiplicity of the lowest energy isomer is a singlet ( 2s + 1 = 1 ), while the higher energy isomer prefers the triplet ( 2s + 1 = 3 ) spin state . we note that the structure of au 3 o ( bo 2 ) is entirely different from that of the iso - electronic boric acid ( bo 3 h 3 ) where the b at the center is attached to three o atoms which in turn are terminated with three h atoms . the ground state geometry of the [ au 3 o ( bo 2 )] − cluster ( fig3 ( b 1 ′)) is not only different from that of its neutral counterpart , but it is identical to the higher energy isomer ( fig3 ( b 2 )) of the neutral species . on the other hand , the higher energy isomer ( δe = 0 . 74 ev ) of [ au 3 o ( bo 2 )] − cluster ( fig3 ( b 2 ′)) is identical to the ground state geometry of its neutral counterpart ( fig3 ( b 1 )). both these anionic isomers prefer a doublet ( 2s + 1 = 2 ) spin state . in both auo ( bo 2 ) and au 3 o ( bo 2 ) clusters , the bo 2 moiety retains its structural identity . moreover , the ground state geometry of [ au 3 o ( bo 2 )] − can be viewed as a [ auo ( bo 2 )] − cluster bound to a au 2 . the photoelectron spectrum of the [ au 3 o ( bo 2 )] − cluster is given in fig4 and compared with that of [ au 3 ( bo 2 )] − . introduction of an o atom into the [ au 3 ( bo 2 )] − clusters dramatically increases the ebe to anomalously large values of 5 ev and beyond . the fact that the [ au 3 o ( bo 2 )] − cluster is an open - shell system ( doublet spin multiplicity ) makes this anomalous increase of ebe even more dramatic . most interestingly , changing the central metal core in auo ( bo 2 ) to au 3 o ( bo 2 ) has resulted in a significant increase in the ade and vde values of the cluster . the large differences in the neutral and anionic ground state geometries of the au 3 o ( bo 2 ) cluster are manifested in the pes data . our calculated vde of 5 . 01 ev , resulting from the transition of the anionic doublet state to the neutral triplet state , is in very good agreement with the experimental value of 5 . 2 ev . however , our calculated ea of 4 . 19 ev does not match with the experimental ade of 4 . 9 ev . this is because the resulting neutral does not automatically reach its ground state structure , but rather remains in a higher energy isomer that is structurally similar to the anionic ground state when the electron is detached from the ground state anionic cluster in the pes experiments of [ au 3 o ( bo 2 )] − . in this process , the electron detachment results in the transition to the potential energy surface of the higher energy isomer that is identical to the ground state anion , but not the ground state of the neutral species . to verify this observation further we calculated the theoretical ade , as the energy difference between the ground state anion ( fig3 ( b 1 ′) and the structurally identical higher energy neutral isomer ( fig3 ( b 2 )). this value is 4 . 86 ev and agrees very well with the experimental ade (˜ 4 . 9 ev ). the second peak in the pes ( see fig4 ) originates from the transition of the spin doublet anion ground state to the spin singlet neutral cluster having the anion geometry . this energy is calculated to be 5 . 72 ev which again matches very well with the position of the second peak . the anomalously large vde and ade values of [ au 3 o ( bo 2 )] − cluster can be explained from the nbo charge analysis . in the case of the neutral cluster ( fig3 ( b 1 )), all three au atoms lost charge to the oxygen atom and the bo 2 moiety , with the au atom bound to both o and bo 2 leading with a charge loss of − 0 . 881e . this charge transfer from au atoms to two highly electronegative entities ( o and bo 2 ) resulted in a total positive charge of + 1 . 396e on the au atoms . it is noteworthy here that in case of the au 3 ( bo 2 ) isomer , the total nbo charge on the three au atoms was only + 0 . 791e [ 21 ], while in the case of auo ( bo 2 ) cluster , the total charge on the au atom is + 0 . 952e . in the case of the anionic cluster , the extra electron is distributed mostly on the positively charged au atoms , with a minority of charge going to the o atom and the bo 2 moiety . the distribution of the extra electron (− 0 . 762e ) over all the three au atoms in [ au 3 o ( bo 2 )] − resulted in a large binding energy of the extra electron , thus yielding large values of vde and ade . on the other hand , in the [ auo ( bo 2 )] − cluster , the extra electron is mostly localized on the au (− 0 . 392e ) and the terminal o (− 0 . 41e ) bound to au , thereby resulting in ade and vde values lower than that of the [ au 3 o ( bo 2 )] − cluster . the fact that the electron affinity of au ( bo 2 ) and au 3 ( bo 2 ) are nearly the same ( see fig6 , table ) while that of au 3 o ( bo 2 ) is about 1 ev larger than that of auo ( bo 2 ) suggests that the central metal core may play a role in the design of hyperhalogens , but it is not universal . in summary the electron affinity depends on the nature of the decoration of the metal atom . a superhalogen is created when the metal atom is decorated with halogen / oxygen atoms and its electron affinity is larger than that of the constituent halogen atoms . in contrast , a hyperhalogen is created when the metal atom is decorated with superhalogens and its electron affinity is even higher than that of the constituent superhalogen . in some cases , replacing the central metal atom by a metal cluster also permits the electron affinity to increase . similarly , by choosing different superhalogen building blocks with electron affinities larger than that of bo 2 , hyperhalogens with even higher electron affinities can be achieved . it is also possible that if the central atom is a transition metal atom , the hyperhalogen can even carry a magnetic moment and the corresponding material could lead to a ferromagnetic insulator if these moments align in parallel . this example has demonstrated that a new class of highly electronegative species can be designed and synthesized by tailoring both the superhalogens building blocks and the central metal core . experimental : the pes experiment was conducted by crossing a mass - selected beam of negative ions with a fixed - frequency photon beam and energy analyzing the resultant photo - detached electrons . it is governed by the energy - conserving relationship , hv = ebe + eke , where by is the photon energy , ebe is the electron binding ( transition ) energy , and eke is the electron kinetic energy . our apparatus , which has been described previously [ 31 ] consists of a pulsed arc cluster ion source ( pacts ), a time - of flight mass spectrometer for mass analysis and mass selection , an f 2 excimer laser operating at 7 . 9 ev for photo - detachment , and a magnetic bottle type electron energy analyzer . the electrodes in the pacts source are mounted in a boron nitride cube . when oxygen was added to the carrier gas from an additional pulsed valve , we observed a strong progression of b containing au n o m clusters in addition to the signals of the au n o m − species . the boron nitride of the cube is eroded by the o 2 - containing plasma . without oxygen , no boron contamination is observed in the mass spectra . we saw no peaks associated with n , even though our mass resolution of m / δm ˜ 1000 is sufficient to distinguish nitrogen from oxygen compounds . the resulting anions were then subjected to extraction and mass analysis / selection . from the experimental photoelectron detachment data , the threshold energies and the vertical detachment energies can be estimated . the threshold energy is determined by fitting the signal increase at low binding energy to a linear function . the intersection of this line with the axis is taken as the threshold energy . if the change in the ground state geometry between the anion and the neutral is not too large , the threshold energy can be compared to the calculated electron affinity ( ea ) which is the energy difference between the ground states of the anion and corresponding neutral . if the geometry of anion and neutral differs significantly , then the threshold energy is compared to the calculated adiabatic detachment energies ( ade ). the vertical detachment energy ( vde ) is taken as the binding energy of the first maximum at lowest binding energy . computational : the calculations were carried out using dft and generalized gradient approximation ( gga ) for exchange - correlation energy functional . we used the b3lyp functional and 6 - 311 ++ g ( 3df ) basis set for b and o atoms and the sdd basis for au atoms as implemented in gaussian 03 code [ 32 ]. the latter basis functions include scalar relativistic corrections . the equilibrium geometries of neutral and anionic au ( bo 2 ) 2 , auo ( bo 2 ) and au 3 o ( bo 2 ) clusters were calculated by optimizing various initial structures without any symmetry constraint . the stability of these clusters was confirmed by analyzing their normal mode frequencies , which are all positive . while the invention has been described in terms of its preferred embodiments , those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims . 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