FULL PAPER 514 solutions withconcentrationssimilartobiologicallyimportantenvironments. alcohol matrixwherethedetectionofsodiumionsisachievedinaqueoussalt solid statesensorbasedonblendsofthedetectingpolymerwithapolyvinyl chains. Thisdesignconceptisfurtherevolvedtodevelopasodium-salt in polarsolventsfacilitatedbytheattachmentofethyleneglycolside small moleculeanalog.Ionselectivityisretainedinpolymerswithsolubility detector unithasahighersensitivityforalkalimetaliondetectionthanits angle ofmorethan70°isobserved.Inaconjugatedpolymerstructure,the and withoutalkalimetalionsiscarriedoutadifferenceofthedihedral or potassiumionsisfound.X-raydiffractionanalysisofsinglecrystalswith UV–vis andNMRspectroscopywherearemarkableselectivitytowardsodium tion andtheresultingbackbonetwistofdetectorunitisinvestigatedby and incorporatedintoaconjugatedaromaticstructure.Thecomplexforma- bithiophene unitischosenasthedetectingunit,bothasmallmolecule molecules andconjugatedpolymersforopticalionsensing.Acrownether This paperpresentsthedevelopmentofalkalimetalionselectivesmall wileyonlinelibrary.com state. Thesyntheticfreedomfordesigningpolymerswithion for thefabricationofopticalsensorsinsolutionandsolid selectiveconjugatedpolymersareexcellentmaterials Introduction 1. Malliara G. George Sirringhaus, McCulloch Henning Iain White, and J.P. Andrew Mindaugas Harkin, Rivnay , J. Jonathan David Nielsen, B. Christian Giovannitti,* Alexander for OpticalIonDetectioninSolutionandSolidState andPotassiumIonSelectiveConjugated Polymers abig B 0E UK 0HE, CB3 Cambridge University ofCambridge Department ofPhysics D. J.Harkin,Prof.H.Sirringhaus France 13541, Gardanne MOC, CMP-EMSE, École NationaleSupérieuredesMines Department ofBioelectronics any medium,providedtheoriginal work isproperlycited. Attribution License,whichpermitsuse, distributionandreproductionin This isanopenaccessarticleunder thetermsofCreative Commons [+] Dr. J.Rivnay, [email protected] E-mail: UK 2AZ, SW7 London Imperial College London and Centre for PlasticElectronics Department ofChemistry Dr. A.J.P.White,Prof.I.McCulloch A. Giovannitti,Dr. C.B.Nielsen,Dr. M.Kirkus, www.afm-journal.de DOI: 10.1002/adfm.201503791 Present address:PaloAltoResearch Center, PaloAlto, CA94304,USA [+] Prof.G.Malliaras © 2015TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim

in thevisiblelightspectrum. sodium ionsinbothsmallmolecules third andfourthpositionsofthiopheneshowselectivitytoward a switchablemolecularwiretriggeredbysodiumsalts. wasreported. was postulatedandanionselectiveresponsewithalkalimetal where aconformationalchangeinducedbyalkalimetalions the 3-and3′-positionsof2,2-bithiophenewasdemonstrated, and Hg to aconjugated rapid andselectivesensingwhenthecrownetherisattached An opticalsensorbasedoncrownethershastheadvantageof ability forcomplexationofvariousions,suchasPb ation intheheteroatomsofcrownetherdemonstrated and -saltdetectionin solutionandsolidstate,based tion ofvisiblesensormaterials forhighlyselectivesodium- typical inhealthmonitoringand earlydiseasediagnosis. muscle cells.Detectionofdeviations intheirconcentrationsis lular fl uids andisespeciallyvitaltotheactivityofnerve important forelectrolytebalanceinextracellularandintracel- The concentrationofcationssuchassodiumandpotassium is of ionsiscriticalforenvironmentalandhealthmonitoring. development ofsensorsforsensitiveanddynamicmonitoring In thisworkwepresentthedevelopmentand characteriza- 2+ . [ 14] Anapproachbasedonacrownetherattached in π -electron systemwhichabsorbsand/oremits [ 15] ecules. solutions isbyusingcrownethermol- tivity foralkalimetalionsinpHneutral most effi be triggeredbychangingthepH. on ionexchangemembraneswhichcan selective opticalsensorsisusuallybased of previouslyreportedalkalimetalsalt for opticalsensors.Theworkingprinciple makes thesematerialshighlyinteresting selectivity andsolutionprocessability and potassiumionsinbloodfl potentiometric measurementsofsodium allowconcentration-dependent selective membranescomprisingcrown stability ofthecomplex.For example,ion and thealkalimetaliondetermine the saltunderacidconditions. selective dyewhichformsacomplexwith material isusuallyaprotonatedcation of severalcomponents,whilethesensor disadvantage isthattheynormallyconsist Thisapproachwassubsequently usedas [ 6] Thesizeofthecrownetherring [ 10] cient waytocreateionselec- Crown ethersattachedinthe Adv. Funct. [ 11] andpolymers. www.MaterialsViews.com Kirkus Mater. , , s 2016, , 2+ 26, 514–523 uids. [ 3–5] , [ 12] [ 13] [ 1,2] [ 16] Vari- The Ag The The [ 7–9] + ,

FULL PAPER 515

6 ). C. [ 15 ] 12 . ° [ 15 ] was 11 at ) and 9 20 , DMF, while and which 3 4 [ 15 ] 5 [ 17 ] CO 2 n -BuLi, LiCl, , DME [25%] 2 Ts, K Ts, 5 is presented 12 wileyonlinelibrary.com ), h) 10 www.afm-journal.de O) 2 was achieved by was achieved by 10 -BuLi and CBr -BuLi -BuLi in THF over 3 h -BuLi CH n -BuLi, CuCl 2 n n = 2: -dimethylformamide -dimethylformamide (DMF) The bromination was only The bromination , N [ 18 ] O (5:1) [41%] ( 2 5 ), m N ), b) TsO(CH ), b) TsO(CH 2a -bromosuccinimide (NBS) at − -bromosuccinimide N to 61% (compared to 36% lit. (compared to 36% lit. to 61% 4c Me, EtOH:H 3 , DME [18 %] ( 2 O) 2 CH 2 in high purity in order to facilitate poly merization. poly in high purity in order to facilitate 12 n -BuLi, CuCl (Scheme 1 , steps b–d) based on the literature , steps b–d) based 1 (Scheme 4c C with an excess of fi ve equivalents C with an excess of fi ° = 1: ]dithiophene-2,6-diyl)bis(trimethylstannane) ]dithiophene-2,6-diyl)bis(trimethylstannane) 78 ′ m achieved full conversion to the desired distannylated product achieved full conversion to the desired distannylated in Scheme 1 The formation of the BDT unit with methyl- The formation 1 in Scheme glycol side chains endcapped triethylene procedure. following a literature mainly isolated. It was necessary to prepare the distannylated mainly isolated. It was necessary to prepare monomer exchange of It was found that only the halogen–metal − A variation in the reaction route was chosen for the interme- was chosen for the in the reaction route A variation diate alkoxy-bithiophenes afforded the head-to-head-coupled units were subse- . The electron-rich bithiophene 1 in Scheme quently brominated with glycol(TEG))benzo[1,2-b:4,5- The synthesis of (4,8-bis(triethylene b with NBS reversed the bromination under acidic conditions and the starting material 1 rst reaction in Scheme the fi possible under alkaline conditions with possible under alkaline avoided the air-sensitive copper(I)-mediated alkoxylation. A copper(I)-mediated avoided the air-sensitive in the two positions of the thiophenes selective ring closure improved the yield of improved 2.2. Characterization of the Backbone Twist shows an illustration of the formation of the com- Scheme 2 (17-Crown-5)T2, plex between the synthesized small molecules catalyst loading of 15 mol% in of 15 mol% in catalyst loading achieved the highest yield (41%, compared to 32.5% lit. compared to 32.5% highest yield (41%, achieved the ), e) 4c ), g) Zn, NaOH, TsO(CH ), g) Zn, NaOH, TsO(CH 8 [54%] ( 3 12 ). O, pyridine, [65%] ( 2 were synthesized. 4c . Conditions: a) tetraethylene glycol, NaH, CuI, DMF [42%] ( . Conditions: 12 cient ion penetration into cient ion penetration into and 2a = 2: NBS, CHCl 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2015 The Authors. Published by WILEY-VCH Verlag ), d) Cu 4b © SnCl, THF [23%] ( 7 , and 8 3 7 ), m . For both small molecules the thio- both small molecules the . For [47%] ( ]dithiophene (BDT) were synthesized (BDT) were synthesized ′]dithiophene 3 n -BuLi, Me O:EtOH, [98%] ( 2 26, 514–523 Scheme 1 b :4,5- b ), i) 11 2016, Synthesis of molecules = 1: NBS, CHCl anked glycol intermediates ), c) KOH, H 4a m ,THF [39%] ( 4 ), f) 6 The synthesis of the dibrominated crown functionalized The synthesis and (20-Crown-6) bithiophene small molecules (17-Crown-5)T2 T2 is shown in 2. Results and Discussion 2.1. Synthesis and Characterization the bulk conjugated polymer. polymer. the bulk conjugated and a detailed structural characterization of the complex forma- of the complex structural characterization and a detailed Selectivity salts was performed. tion with different ions was observed for different toward sodium or potassium of the small molecules with the excel- crown ether ring sizes to in the corresponding polymers. Next lent selectivity retained maximum, a shift of the emis- a blue shift of the absorption was also observed when alkali metal sion peak to higher energy of an optical also present the development ions were added. We sensor working in aqueous solution uti- sodium ion solid state copolymers comprising highly polar side lizing the crown ether The formation polyvinyl alcohol (PVA). chains in a blend with allows effi of hydrogel morphology on conjugated aromatic crown ether bithiophene materials. ether bithiophene aromatic crown on conjugated copolymers molecules and bithiophene small ether Crown with benzo[1,2- phene-fl A reaction screening for the intermediate 2a was carried out A reaction screening for the intermediate of 3-bromothiophene to increase the yield of the alkoxylation , step a) and it was found that CuI as the catalyst and a 1 (Scheme Mater. Funct. Adv. [95%] ( Scheme 1. ( CBr www.MaterialsViews.com FULL PAPER 516 with KClO plex). UV–visspectroscopytitration experimentsof(17-Crown-5)T2 and (20-Crown–6)T2 withNaClO Figure1. thiophenes areincloseproximitywitheachother. form aconformerwherethetwooxygenatomsattachedto (20-Crown-6)T2-MX requiresatwistofthebithiopheneunitto (20-Crown-6)T2 andalkalimetalsaltsMX(M=Na,K;X wileyonlinelibrary.com Scheme2. tals withandwithoutalkalimetalsaltstoinvestigatethechange NMR spectroscopyaswellX-ray diffractionofsinglecrys- BPh www.afm-journal.de This conformationaltwistwasmonitoredbyUV-vis and 4 ). Theformationofcomplexes(17-Crown-5)T2-MX and Complex formation andstabilitycomplexconstant(ligandListhesmallmolecule,MX salt,andL(M):Xrepresentsthe formed com- 4 Formation ofthecomplexesandresultingbackbonetwist. (c,d)inacetonitrileat25°C. © 2015TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim

= ClO 4 , a corresponding50nmblueshiftoftheabsorptionmaximum twisted complexstructurewithpotassiumsalts(Figure 1 b), and that thelargermolecule(20-Crown-6)T2 exclusivelyformsthe salts, Supporting Information).Ontheotherhand,itwasfound or potassiumperchlorateswereadded(Figure 1 c), (seriesofall changes oftheopticalpropertieswereobservedwhenlithium NaClO maximum wasobservedwhen(17-Crown-5)T2 wastreatedwith 4 withanisosbesticpointat310nm(Figure 1 a), whileno tally. Ablueshiftof40nmtheabsorption MClO tonitrile at25°Cwhentheconcentrationof responses ofthesmallmoleculesinace- the complexationreactionandoptical the concentrationofMX. absorption wasmonitoredasafunctionof troscopy titrationexperimentswherethe alkali metalionswasstudiedbyUV-vis spec- The selectivityofthesmallmoleculestoward tivity andsensitivityofthesmallmolecules. salts insolutionwasvariedtoanalyzeselec- ticular, theconcentrationofalkalimetal rings insolutionandthesolidstate.Inpar- of thedihedralanglefusedthiophene 4 (a,b)and(17-Crown–5)T2 and(20-Crown-6)T2 4 (M = Na,K)wasincreasedincremen- Adv. Funct. www.MaterialsViews.com Mater. shows 1 Figure 2016, 26, 514–523 FULL PAPER 517 eld

wileyonlinelibrary.com www.afm-journal.de . All spectra are referenced . All spectra 4

a, the protons C and D [ 21,22 ] H NMR measurements were 1 C shifted protons B, C, and D Figure 3 a where the crown ether protons (A–D) asa where the crown was increased in deuterated acetonitrile. Before 4 Figure 2 Temperature-dependent [ 23 ] To get a better understanding of the side complexation reac- of the side complexation get a better understanding To the addition, all crown ether protons of (17-Crown-5)T2 are highly the addition, all crown ether protons of (17-Crown-5)T2 The resolveda). 2 resolved (labeled A, B, C, and D in Figure of protons C and D aresignals and shift toward lower frequencies the protons arefurther evidence for a planar structure because induced magnetic fi located above the aromatic system and the of the aromatic system shields the protons. During the salt addi- of the aromatic system shields the protons. toward lower frequen- tion, the chemical shift of proton A shifts electron density due tocies which is consistent with a decrease of to the metal ion. Sur- the charge transfer from the atoms protons C we observed a shift to higher frequencies for prisingly, and the signalsand D when the salt concentration was increased the signalsbecome less resolved while at high salt concentrations the same chemicaleven merge together where both protons have environment. As illustrated in are only located above the aromatic system in a planar structure while the aromatic ring current of the twisted aromatic bithio- b). 3 phene structure does not affect the protons (Figure carried out to investigate a conformational change from a planarcarried out to investigate a conformational It was found thatto a twisted structure at higher temperature. a temperature difference of 50 ° unaffected. This shiftto higher frequencies while proton A was of the conforma- of the protons B, C, and D indicates a change ofb shows the response 2 Information). Figure tion (Supporting when the concentra- the crown ether protons of (17-Crown-5)T2 tion of NaBPh result of a decreased conjugation length of the aromatic system. length of the aromatic decreased conjugation result of a where complexation reaction could be a side Another reason structure crown ether but the ion is stabilized by the the metal a backbone twist. does not undergo tion, a detailed NMR spectroscopy study was carried out withtion, a detailed NMR metal and different alkali and (20-Crown-6)T2 (17-Crown-5)T2 of the small molecule (17-Crown-5)T2 salts MX. The structure is shown in protons (E) are labeled. Protons A nearestwell as the aromatic system are highly deshielded andto the electron-rich aromatic at higher frequencies (4.3 ppm) while pro- have a chemical shift (3.37 and 3.26 ppm) but surprisinglytons C and D are shielded a resolution of the signals indicates resolved. This unexpected in solution which can of (17-Crown-5)T2 planarized structure oxygen interactions of the bithiophenebe explained by sulfur unit. and addition of up to 87 equivalents of NaBPh and addition 3 d

d) )] –1

ε Δ cm 4383 –1 M [( NMR measure- c) ) [ 19 ] 4 ] – 3279 – −1 c) a) b) 2.41 K (KClO . [L mol 4 log 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2015 The Authors. Published by WILEY-VCH Verlag

© ) when the twisted , Table 1 4

) 4 ] 3.38 – 5.46 −1 conductivity measurements; c) a) b) b) – K (NaClO [L mol log 26, 514–523 and protons A–D are highlighted. 2016, 3 d 4.21 4.44 after addition of 50 equivalents of MClO [19] [20] a) Molecular structure of (17-Crown-5)T2 with labeled hydrogen atoms A–E, b) titration experiment analyzed by NMR spectroscopy, crown hydrogen atoms A–E, b) titration experiment analyzed by NMR spectroscopy, with labeled a) Molecular structure of (17-Crown-5)T2 d) Stability complex constants for the sodium and potassium constants for the sodium Stability complex [ 20 ] cients of the functionalized bithiophenes substantially the functionalized bithiophenes substantially cients of The stability constants are lower than their respective crown The stability The stability constants for the sodium and potassium salt The stability constants Calculated from UV–vis data; Calculated 17-(Crown-5)T2 2.58 20-(Crown-6)T2 18-Crown-6 18-Crown-6 15-Crown-5 15-Crown-5 complexes were formed. This can be explained by a conforma- complexes were formed. This can be explained dipole moment of tion change resulting in a lower transition structure, due to the twisted structure compared to the planar reduced molecular orbital overlap. ments; complexes in acetonitrile at 25 °C. complexes in Table 1. 1. Table Information) and are listed in Table 1 . We compare them . We data (Supporting complexes were derived from the UV–vis 1 Information) and are listed in Table and (15-Crown-5) to 1,4,7,10,13-pentaoxacyclopentadecane which (18-Crown-6) 1,4,7,10,13,16-hexaoxacyclooctadecane sodium and potas- have high complexation tendencies for and , 15-Crown-5 1 As shown in Table sium salts, respectively. form highly stable complexes with sodium and/ 18-Crown-6 of these materials for or potassium salts which limit the usage constants stability highly selective measurements. The complex usage due to a lack are very high which limits the long term our materials. For of reversibility of the complexation for these for either sodium synthesized materials the optical selectivity is or potassium salts (20-Crown-6)T2 salts (17-Crown-5)T2 highly interesting for remarkable and makes the materials sodium complex with optical sensors. It was found that the higher stability than the potas- has a slightly (17-Crown-5)T2 sium complex with (20-Crown-6)T2. ether analogs due to the electronic nature where the twist of the thiophenes forms a conformation with a higher energy as a a) was observed with an isosbestic point at 306 nm. The extinction isosbestic point at 306 nm. The extinction was observed with an coeffi 22% for (20-Crown-6) and (17-Crown-5)T2 decreased (41% for T2 after 50 equivalents MBPh

Mater. Funct. Adv. to acetonitrile- ether protons of (17-Crown-5)T2 in the region of 4.3–2.9 ppm in acetonitrile- ether protons of (17-Crown-5)T2 Figure 2. www.MaterialsViews.com FULL PAPER 518 of (20-Crown-6)T2 withNaBPh of thetwistedstructureandthisalsoprovesthatinteraction that thearomaticprotonsEarehighlyaffectedbyformation 0.036 ppmafteradditionof15equivalentssalts.Thisshows of thesignalsuntwistedcomplexwereonly0.041and T2 whenthetwistedcomplexeswereformed,whileshifts E shifted0.10ppm(17-Crown-5)T2 and0.12ppm(20-Crown-6) plex. AsshowninFigure 3 c, thesignalsofaromaticprotons found whenthesaltwasaddedwhichformtwistedcom- difference inthechemicalshiftsofaromaticprotonsEwas for thelowcomplexstabilityconstants.However, asignifi forming thetwistedcomplexesprovidesanotherexplanation crown etherunitsalsointeractwiththeaddedsaltswithout plex withKClO (20-Crown-6)T2 increasesfrom 14.0°to84.6whenthecom- wileyonlinelibrary.com aromatic system.c)ChangeofthechemicalshiftprotonsEwhentwistedoranuntwistedcomplexisformedinacetonitirl Figure3. complex structureasdescribedabove. the smallmolecule(20-Crown-6)T2 donotformthetwisted plex formationwithsodiumandpotassiumsaltsalsowhen due totheslightlylargercrownetherwhichallowscom- T2 interactedwithbothsodiumandpotassiumsaltswhichis the potassiumsalt.Thecrownetherprotonsof(20-Crown-6) when sodiumsaltwasaddedwhileaminorshiftfoundfor crown etherprotonsof(17-Crown-5)T2 onlyshiftedstrongly troscopy andcomparedtoeachother. Itwasfoundthatthe parison, Supporting Information)wasmeasuredbyNMRspec- (20-Crown-6)T2 towardsodiumandpotassiumsalts(saltcom- when theNaBPh Crown-5)T2 wasobservedwhile theangleincreasesto75.9° and withoutalkalimetalsalts. A dihedralangleof3.2 crystal structuresof(17-Crown-5)T2 and(20-Crown-6)T2 with their alkalimetalsaltcomplexes. investigate themolecularstructuresofcrownethersand Information). (Supporting T2 areanotherevidenceforachangeoftheconformation Nuclear overhausereffect(NOE) experiments for(17-Crown-5) plex structureandonlyinteractswiththecrownetherprotons. www.afm-journal.de The responseofthesmallmolecules(17-Crown-5)T2 and Single crystalX-ray diffractionanalyseswerecarriedoutto a) Planarstructureof(17-Crown-5)T2: ProtonsCandDareabovethearomaticsystem.b)Twisted structure:protonsareless 4 isformed. 4 complexisformed. Thedihedralangleof

4 doesnotformthe twistedcom- 4 Figure showsthemolecular © 2015TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim [ 20] Ourfi nding thatthe ° for(17- cant obtained withrespectablemolecularweights( with triethyleneglycolsidechains.Polymers in thestructure. indicating thesuccessfulincorporationofcrownetherunits P4 showedseveralrepeatingunits(Supporting Information) tion–time-of-fl maximum wasobservedwhenNaBPh shown in with 5-ethylhexyl-2-thienylsidechainsandpolymers containing either5-ethylhexyl-2-thienyl different typesofdistannylatedBDTmonomers wereprepared tigate sodium-andpotassium-selectivesensormaterials.Two rating theionselectivemonomersinbackbone,toinves- encouraged ustosynthesizeaseriesofpolymersincorpo- toward sodiumandof(20-Crown-6)T2 towardpotassium The highselectivityofthesmallmolecule(17-Crown-5)T2 Polymerization 2.3. metal saltsMBPh The UV–vistitration experiments ofpolymer Properties Optoelectronic 2.4. M P3 and whereas lowermolecularweightswereobtainedforpolymers tannylated BDTmonomers molecules (17-Crown-5)T2 and(20-Crown-6)T2 withthedis- in catalyzed Stillepolymerizationinchlorobenzeneasillustrated acetonitrile. AlternatingcopolymersweresynthesizedbyPd- which willallowprocessingfrompolarsolvents,e.g.,DMFor unit wassynthesizedtoachievesolubilityinpolarsolvents, cessing fromnonpolarsolvents.ThetriethyleneglycolBDT common conditionsforStillepolymerizationandallowpro- The alkylatedBDTmonomerwaspreparedinordertousethe M w w

3. Scheme = 6.0kDafor = 73kDafor (M P4 5 Figure . Ablueshiftof75nmtheabsorption ight (MALDI–TOF)massspectrometryof n [ 25]

= 3.2kDa,

We copolymerizedthedibrominatedsmall 4 P4 ). Matrix-assisted laserdesorption/ioniza- (M , M P1 , = Na,K)intetrahydrofuran(THF) are n M

[ 26] = 30kDa, w

toaffordpolymers = 5.6kDafor Adv. Funct. 4 [ 24] wasadded(Figure 5 a). M www.MaterialsViews.com orTEGsidechains. w

Mater. = 44kDafor , M P3 , e- P1 and d 3 M . P1 andalkali 2016, affectedbythe n n

P1 and

= 26kDa, = 3.6kDa, P3 and 26, 514–523 were P2 and P3 P2 ) P4 P2 FULL PAPER 519

4 −1

cient of also shows a P4 are selective P4 wileyonlinelibrary.com www.afm-journal.de . When KBPh . When KBPh P1

were carried out and 4 and P2 have the highest selec- P3 as well as the small mole- as well as P1 – P4 and P1 summarizes the responses of the summarizes Table 2 the emission spectrum shifts 76 nm toward the emission spectrum d). 5 higher energy (Figure tivity and only form the twisted complexestivity and only form with sodium salts. toward potassium salts while 10 nm shift when 200 equivalents of sodium byions were added, which can be explained saltinteraction of the crown ether and the aswhich does not twist the structure similar found for the small molecule (20-Crown-6)T2 and sodium ions. More polar solvents such as DMF solubilize the alkali metal salts better by aand lower the complex stability constant Information). factor of 1000 (Supporting polymers and potassium salts incules toward sodium the sodium selectiveTHF. It was found that polymers restored. Similar to the analogous small the analogous small to Similar restored. coeffi cules units, the extinction mole complex was decreased while the the polymer 50 µg mL low concentration of formed. A 2.5. DFT Calculations the energy of the highest occu- calculated We pied molecular orbital (HOMO) of a mol- T2 ecule consisting of three BDT and two is used for the titration of is used for change was observed was added, no color (Figure 5 b). ments with NaBPh Photoluminescence measure- units by using hybrid density functional theory (DFT) calcula- units by using hybrid density functional The HOMOs level of theory. tion in vacuum at B3LYP/6-31G(d) stabilized by one acetonitrile molecule 4 stabilized by two THF molecules (counter ion not 4 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2015 The Authors. Published by WILEY-VCH Verlag © 26, 514–523 2016, Synthesis of polymers P1–P4. a) Crystal structure of (17-Crown-5)T2. b) Crystal structure (20-Crown-6)T2. c) Crystal c) Crystal structure (20-Crown-6)T2. b) Crystal structure of (17-Crown-5)T2. a) Crystal illustrated). d) Crystal structure (20-Crown-6)T2:KClO structure (20-Crown-6)T2:KClO illustrated). d) Crystal and one perchlorate ion (solvent molecules and counter ion are faded). and one perchlorate ion (solvent molecules and Figure 4. structure of complex (17-Crown-5)T2:NaBPh To demonstrate reversibility, 15-Crown-5 was added at the 15-Crown-5 reversibility, demonstrate To absorption peak was end of the titration series and the initial Mater. Funct. Adv. Scheme 3. www.MaterialsViews.com FULL PAPER 520 THF. ecules ((17-Crown-5)T2, (20-Crown-6)T2) towardMBPh Table 2. wileyonlinelibrary.com www.afm-journal.de after additionof300equivalentsNaBPh of thepolymer. to thesodiumionswhichalsoaffectsionizationpotential urements canbeexplainedbyachargetransferfromtheligand sodium saltswerepreloadedintothethinfi the ionizationpotentialincreasedfrom−4.8to5.6eVwhen NaClO DFT theory. Theionizationpotentialsof the crystalstructurewithoutsalttouseasimplelevelof structure werecarriedoutstartingfromthedataobtained be for theplanarandtwistedstructurewerecalculatedto Figure5. P3 P2 P1 (17-Crown-5)T2 P4 (20-Crown-6)T2 The largerionizationpotentialobtainedfromthePESAmeas- −4.59 and5.06eV, respectively. Calculations forthetwisted Absorption 4 Optical responses ofthepolymers(P1–P4)andsmallmol- weremeasuredbyphotoelectronspectroscopyand Titration experimentsofP1andMBPh 6 Figure [nm] 339 558 542 336 520 510 illustratesthespatialdistributionsof max. © 4 2015TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim , d)PLshiftwithNaBPh Shift inUV–vis 75-Na 40-Na 54-Na [nm] 50-K 40-K 64-K P3 withandwithout 4 lm. (M = Na,K)inTHF,a)additionofNaBPh 4 (M = Na,K)in Shift inPL 76-Na 63-Na [nm] 20-K 32-K 4 – – . decrease inconjugationlengthwhenthestructureistwisted. the HOMOsofplanarandtwistedstructureshows fi molecule hastheadvantagethatsensitivityisampli- An opticalsensorcomprisingapolymerratherthansmall Measurements Sensitivity 2.6. toward NaBPh responses ofsmallmolecule(17-Crown-5)T2 andpolymer crown etherligandalongthebackbone. cient andabsorptiononsetof polymer to thetwistedcomplexside. centration ofsaltisnecessary to shiftthereactionequilibrium and sensitivity. For asmall moleculebasedsensorahighercon- before thesaltadditionhigher willbetheresponsesignal the higherconjugationlengthofcrownetherpolymers and scaleswiththenumberofconjugatedunits.Thismeans salts onabsorptionandextinctioncoeffi units alongthebackbone,andthuseffectofalkalimetal each crownetherbithiopheneisinconjugationwiththeBDT be explainedbyconsideringthatinthecaseofpolymer, trations whilethesmallmoleculeshowsnochange.Thiscan onset energyofthepolymeralreadyshiftsatlowersaltconcen- ed bythenumberofconjugatedrepeatunitscontaining Figure 7 c presentsthechangeofextinctioncoeffi 4 and15-Crown-5, b)additionofKBPh 4 inTHF.Itwasobservedthattheabsorption

Adv. Funct. P3 andsmallmolecule , sos the shows 7 a,b Figure www.MaterialsViews.com cient iscooperative Mater. 4 , c)colorchange 2016, 26, 514–523

P3 - FULL PAPER 521 ). λ

− uid:

uids 0 λ

=

λ Δ -axis shows the X wileyonlinelibrary.com www.afm-journal.de in THF, b) polymeric structure, and in THF, b) 4 ). This can be achieved by a polymer [ 27 ] M

-axis: difference in absorption onset -axis: difference in absorption onset −3 Y × 10 ). Right ε –145 −

0 −3 ε

=

ε × 10 Δ 135 outperforms the small molecule and shows the advantage of outperforms the small molecule and shows rather than a an optical sensor based on a polymeric structure the ion selective poly- small molecule. The detection range of of the desired appli- mers can be adjusted to the requirements where the com- cation by the synthetic design of the polymer sensitivity range. For plex stability constant will determine the in extracellular fl example, the detection of sodium ions sensitivity in the mil- requires a detection range with a peak in extracellular fl limolar range (sodium concentration structure based on a similar detector unit as (17-Crown-5)T2 as (17-Crown-5)T2 structure based on a similar detector unit with a similar complex stability constant and (20-Crown-6)T2 and demonstrate that (17-Crown-5)T2 in aqueous solutions. To sodium ions in the polymer P3 retained their selectivity toward presence of other alkali metal ions, titration experiments with a cient (

. M −3 M

−3 −3 P3 is 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2015 The Authors. Published by WILEY-VCH Verlag in THF, c) sensitivity measurements of small molecule (17-Crown-5)T2 and polymer P3. The (17-Crown-5)T2 in THF, c) sensitivity measurements of small molecule 4 cient of the absorption max- © -axis left: difference in extinction coeffi Y and at a concentration of 0.2 × 10 and at a concentration is at a concentration of 0.4 × 10 P3 M in THF. a)

4 −3 26, 514–523 than the small molecule. The peak sensi- M cient is the signal of choice (Figure 7 c, black 7 is the signal of choice (Figure cient

2016, −3 HOMO of the a) planar and b) twisted molecule with three BDT and two T2 units. toward NaBPh of a visible sensor based on a) small molecule and response of (17-Crown-5)T2 Comparison and 1.0 × 10 of polymer The upper detection limit for sodium ions reached at 1.0 × 10 than the small the polymer has a two times larger sensitivity has a higher sensi- molecule. Small molecule (17-Crown-5)T2 When the absorption tivity at lower sodium-salt concentrations. c, blue lines) the polymer 7 onset is the signal of choice (Figure (17-Crown-5)T2 in solution when the concentration of sodium (17-Crown-5)T2 salt is increased (extinction coeffi imum and absorption onset as shown in Figure 7 a,b related to 7 Figure imum and absorption onset as shown in When the change in the concentration of sodium salt in THF). extinction coeffi has a higher sensi- lines) it can be observed that the polymer between 0.2 × 10 tivity toward sodium ions at concentrations tivity for the polymer Mater. Funct. Adv. Figure 6. www.MaterialsViews.com concentration of NaBPh Figure 7. response of polymer P3 toward NaBPh FULL PAPER 522 and preloadedwithNaClO were immersedfor10hinDIwater(blackline),0.1 Figure8. wileyonlinelibrary.com www.afm-journal.de then immersedin0.1 the blendwithmaleicanhydrideat110° Water-insolubility ofthefi lms wasachievedbycross-linking PVA andsodiumselectivepolymer for sodiumions.We preparedpolymer–polymerblendswith Finally, wewereabletodevelopavisiblesolidstatesensor Sensor State Solid 2.7. Information). out andnodecreaseofselectivitywasobserved(Supporting similar totheabsorptionshiftobservedfor0.1 the shiftofabsorptionpeak(blueline)andresult is structural backbonetwistbyUV–vis andNMR measurements depends onthesizeofcrown etherring.We confi sodium orpotassiumionsare presentwheretheselectivity The crownetherunitsonlyundergo abackbonetwistwhen ether bithiopheneionselective smallmoleculesandpolymers. In conclusionwesuccessfullysynthesizedaseriesofcrown Conclusion 3. background concentrationof1.0 drying thefi a shifttowardtheinitialabsorptionpeakwasobservedafter tion, thefilms wereimmersedindeionizedwaterfor10hand solution. To demonstratereversibilityofthecomplexforma- NaClO between 350and450nmwasformed.Apreloadedfi observed asshownin shift oftheabsorptionmaximumtowardhigherenergywas spectroscopy wascarriedoutonthedriedfi lms anda35nm visually observedoncomparisonofthetwofi the fi lms weredriedat100° was observedinwater(Supporting Information)andafter10h ized (DI)waterasareferencefor10h.Hydrogelformation 4 UV–vis spectroscopyoftheopticalsolidstatesensor. Thinfi lms waspreparedunderthesameconditionstocompare lms.

8 Figure M 4 (blueline)anddriedat100°C. aqueousNaClO C. Acolorchangewasalready whileabroadabsorptionpeak © × 10 2015TheAuthors.Published byWILEY-VCHVerlag GmbH&Co. KGaA,Weinheim P3 inamassratioof20:1. −3

M 4 C. KBPh solutionanddeion- [ 28] M NaClO Thefi 4 werecarried ls UV-vis lms. lms were lms M 4 rmedthe (redline), lm with lm NaClO 4

materials isthatinadditiontoPLspectroscopy, pound polymersystem.Theadvantageoftheopticalsensor tion, thepresentedopticalsensorconsistsonlyofaonecom- uprig Information Supporting approaches an equivalentsmallmoleculestructure.Comparedtoother sensitivity increasesinapolymericstructureandoutperforms be observeduponalkaliioncomplexation.We foundthatthe fl into apolymerstructurewhereshiftoftheabsorptionand selectivity ofthecrownetherismaintainedafterincorporating as wellanX-ray diffractionstudyofsinglecrystals.The the fi nancial support. EC FP7ProjectArtESun(604397),andPOLYMED (612538)for We thankEPSRCProjectEP/G037515/1,ECFP7SC2(610115), Acknowledgements from theauthor. Supporting InformationisavailablefromtheWileyOnlineLibraryor fi sodium selectivepolymerintoaPVA matrixtodemonstratethe other alkalimetalions.Finally, wewereabletoincorporatethe ether ringandselectivityisalsoretrainedinthebackgroundof ions canbeadjustedbyvaryingtheringsizeofcrown ions insolution.Theselectivitytowarddifferentalkalimetal UV–vis spectroscopycanalsobeusedtodetectalkalimetal conjugated polymers. 1] .H i , .I og Chem.Commun. Hong, J.-I. Kim, Y.-H. [10] 1] . . Vdrio , . . Uhkv L G u’ia A V Churakov , V. A. Kuz’mina, G. L. Ushakov , Oçafrain, N. M. E. Vedernikov Bricaud, , I. Q. A. Hardouin, [14] M. Smaali, K. Tran , K. Lee , T. B.-L. [13] Kashiwazaki, A. Miyazaki, Y. Omote, M. Yamamoto , T. [12] 1] . Cei , . . Wizug A uln , Hubland, A. Wiirzburg, U. D. Chemie, O. [11] uorescence peakofupto75nmtowardhigherenergycan rst exampleofasolidstateopticalsodiumsensorbasedon 8 G J od , . . Sa , . . Toa , Analyst Thomas, Clin.Chem. D. Arnold, J. a. Saad, M. B. [9] B. Moody , J. G. [8] Clin.Chem. Levy , B. Anal.Chim.Acta G. Patel, J.Am.Chem.Soc. [7] Pedersen, H. J. C. Ma, [6] L. Zhu, L. Wang , Anal.Chim.Acta E. Guo, C. [5] Wang , K. Clin.Chem. Yang , Simon, X. W. Ammann, Wimon, [4] D. W. Oesch, Rusterholz, U. B. [3] Rosatzin, T. Lerchi, M. Bakker , E. [2] 1 T aaht , . Kng , . Ymmt , . Siki Anal.Sci. Shinkai, S. Yamamoto , H. Kunogi, K. Hayashita, T. [1] 85. Chim. Acta 161. 13, . a Srlno M önr A M ru , . . . Howard, K. a. J. Braun, M. A. Wörner , Gromov , P. M. S. Alfimov , V. Strelenko, M. a. Adv. Y. Vuillaume , D. Roncali , J. Godey , S. Lenfant, Mater. S. Blanchard, P. Macromolecules Kubota, K. 7158. Inoue, T.30, Osakada, K. Kanbara, T. , 427. 25, 2013, [ 29] forselectivealkalimetaliondetectioninsolu- , 211. 278, 1993, , 1435. 27, 1981, , 1319. 37, 1991, J. Phys.Org.Chem. Published online:December16,2015 , 2495. 89, 1967, Adv. Funct. Received: September 7,2015 , 512. 2002, Revised: October 29,2015 , 124. 129, 1995, www.MaterialsViews.com , 45. 407, 2000, Mater. , 15. 114, 1989, , 1448. 32, 1986, , 195 . 23, 2010, 2016, [ 29,30] , 357, 1997, 26, 514–523 simple 1997, 1997, Anal. FULL PAPER 523 13 , 2006 , 2009 , 35 , 36 . 2013 , , 46 727 . wileyonlinelibrary.com www.afm-journal.de Ital. J. Pediatr. 2014 , 24 , 1748 . 2014 , 26 , 3009 . 2011 , 52 , 6011 . S.-W. S.-W. Liu , Polymer (Guildf). R. S. T. D. Anthopoulos , , Ashraf I. McCulloch , Macromolecules Y. W. , Soon C. B. Nielsen , J. R. Durrant , F. Huang , Y. , Cao Chem. Mater. 161 . K. , Kyhm H. Y. , Woo Mater. Funct. Adv. 2015 , 7 , 17565 . [27] M. G. Bianchetti , G. D. , Simonetti A. , Bettinelli [24] J.-C. Chen , H.-C. , Wu C.-J. [25] , Chiang L. L.-C. Biniek , Peng , B. T. Chen , C. L. , Schroeder Xing , J. E. , Donaghey N. , Yaacobi-Gross [26] P. Liu , K. Zhang , F. Liu , Y. [28] Jin , J. S. M. Liu , T. Gohil , P. A. Russell , Bhattacharya , H.-L. P. Yip , , Ray J. Polym. Res. [29] B. L. Nguyen , J.-E. [30] Jeong , B. I. Sui , H. X. Jung , , Yue B. B. Kim , Kim , K. V. D. S. eld , Belfi Le , Interfaces ACS Appl. Mater. I. , Kim

New J. 1986 , 121 , 53 . 1993 , , 115 12214 . 1986 , 25 , 1747 . 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim GmbH & Co. 2015 The Authors. Published by WILEY-VCH Verlag 1988 , 17 , 277 . 2008 , 32 , 932 . © 2005 , , 127 15372 . 26, 514–523 2016, 2013 , 37 , 1728 . 2001 , 1 , 1398 . 1988 , 92 , 6233 . O. Ito , Soc. J. Am. Chem. Chem. P. , Frere J. , Roncali New J. Chem. Trans. [22] M. B. Gholivand , M. , Shamsipur Inorganica Chim. Acta [21] S. , Fery-Forgues M. T. Le Bris , J. P. Guette , B. , Valeur J. Phys. Chem. [19] H.-J. Buschmann , J. Solut. Chem. [18] K. Lu , J. , Fang X. Zhu , H. , Yan D. Li , C. Di , Y. , Yang Z. , Wei [16] T. , Oike T. , Kurata K. , Takimiya T. Otsubo , Y. Aso , [17] H. , Zhang J. Y. Araki , D. E. n , Chaffi J. M. , Barker P. R. Huddleston , J. Chem. Soc. Perkin [20] R. D. , Boss A. I. , Popov Inorg. Chem. [23] N. Hergue , P. Leriche , P. , Blanchard M. , Allain N. Gallego-Planas , [15] M. J. Marsella , T. M. , Swager Soc. J. Am. Chem. Mater. Funct. Adv. www.MaterialsViews.com