D10488
`
`A DVAN c E D
`g MATE IAI-
`
`éé é 4
`
`HO
`
`HO
`
`HO
`
`HO
`
`
`
`BF;
`
`BF;
`
`HM
`
`
`iyered Ionic Liquids
`Type Conjugated Polymer for Thin-film Transistors
`idirectional Protonic Conductivity in Soft Materials
`alecular-Recognition Microcapsules
`1
`
`o0
`: \e‘r’ofi\e a”
`$\\G\)\0‘\\)
`$0
`Q
`TFS1081
`
`1
`
`TFS1081
`
`

`

`”tiff-“if
`*°’”Z::7+°"if
`i“
`i“
`’3‘
`a“
`Mfg“ Q5
`mac/\c. 1:10
`I:
`:
`I; M;
`fl%\\ . g’Q-
`.
`-
`. 4' En:
`-
`.
`:
`«a
`:Q‘ 3% M‘ present \‘gy
`
`'0;‘9 Unique molecular-recognition microcapsules
`
`I-
`
`z 1
`
` In
`‘}
`z
`
`con-
`stimuli-responsive
`environmental
`for
`trolled release have been developed. The
`microcapsules consist of a core—shell porous
`membrane. The pores contain linear-grafted
`poly(NIPAM-co-BCAm) chains, which act as
`the molecular-recognition gates. The Figure
`shows the mechanism of the opening of the
`pores to release the molecules inside.
`
`
`L.-Y. Chu, T. Yamaguchi,* S. Nakao
`
`Adv. Mater. 2002.14.386m389
`
`AMolecular-Recognition Microcapsule
`for Environmental Stimuli-Responsive
`Controlled Release
`
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`Adv. Mater, 2002. I4, N0. 5, March 4
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`

`
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`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`(TSA)]_0(PDP)m. the heating cycle was first 1 Kmin'1 from 50 to 110°C and
`another cycle from 60 to 170 “C, which is well above the orderidisorder temper»
`ature, Tom- = 135 “C. For the P4VP(TSA)1,U salt the heating cycle was from
`60 to 170 °C.
`
`Received: August 13, 2001
`
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`
`Energy Transfer in Mixtures of Water-Soluble
`Oligomers: Effect of Charge, Aggregation, and
`Surfactant Complexati0n**
`
`By Martin Stork, Brent S. Gaylord, Alan J. Heeger,
`and Guillermo C. Bazan*
`
`Emissive conjugated polymers are under intense investiga-
`tion for their potential role in chemicallll and biologicallzl sen-
`sors. Intrachain and interchain energy transfer processesl3l al—
`low excitations to sample multiple environmentsl‘ll If one of
`these sites is in close proximity to a fluorescence quencher
`molecule,
`the result
`is an enhancement of the quenching
`event. If removal of the quencher molecule from the vicinity
`of the conjugated polymer can be coupled to the presence of a
`target analyte, one obtains the platform for optical sensing. It
`is difficult for isolated fluorophores to exhibit similar amplifi-
`cation.
`
`Water-soluble conjugated polymerslsl are of particular inter-
`est in biosensor schemeslf’l To compensate for the hydropho-
`bic nature of the backbone, these polymers contain charged
`groups for solubility in aqueous media. The dependence of in-
`terchain aggregation and the coil conformation ShOW behavior
`typical of polyelectrolytes.
`Indeed, many of
`the lessons
`learned from the complexation of surfactants to polyelectro-
`lytesm have been used to tune the optical properties of poly-
`mers such as p01y(2,5-methoxy-propyloxysulfonate phenyl—
`eneVinylene)
`(MPS—PPV).l8l The relationship between the
`charge of the quencher molecule and the efficiency of quench—
`ing has also been studied for a polymer similar to MP8—
`PPV.l9l
`
`[*] Prof. G. C. Bazan, Dr. M. Stork. B. S. Gaylord. Prof. A. J. Heeger
`Departments of Chemistry and Materials
`University of California
`Santa Barbara, CA 93106 (USA)
`E-mail: bazan@chem.ucsb.edu
`
`This work was funded by the MRI. Program of the NSF under Award
`No. DMR 96—32716 and the Office of Naval Research. This work was sup-
`ported by a fellowship within the Postdoctoral Program of the German
`Academic Exchange Service (DAAD). Useful discussions with Prof. Dave
`Whitten and Dr. Deli Wang are gratefully acknowledged.
`
`Adv. Mater 2002, 14, No. 5, March 4
`
`© WILEY-VCH Verlag GmbH, D-69469 Weinheim, 2002
`3
`
`0935-9648/02/0503-0361 $ 17.50+.50/0
`
`361
`
`3
`
`

`

`
`
`
`
`
`
`O(CH2)3SOSNa
`
`MPS-PPV
`
`More recently, energy transfer between oppositely charged
`polyelectrolytes has been used to obtain fluorescence super-
`quenchinglml These mixtures offer possibilities of “charge re-
`versal”, where it is possible to encourage interactions between
`a given polyelectrolyte and a fluorescence quencher with simi—
`lar charge. For example, mixing MPS—PPV with a cationic
`poly-L-lysine with appended cyanine dyes results in a complex
`where energy transfer from MPS—PPV to the dye takes place
`followed by quenching with a negatively charged anthraqui-
`none derivativelml
`im—
`Despite much success in demonstrating applications,
`portant structure—optical properties relationships in water
`soluble conjugated polymer mixtures remain lacking. In an
`analogy to the elucidation of optical properties as a function
`of chainlength for many conjugated polymers,[‘” we com-
`pared the properties of MPS-PPV against those of pentaso—
`dium 1,4—bis(4’(2”,4”—bis(butoxysu1fonate)—styryl)styryl)-2—
`(butoxysulfonate)-5-meth0xybenzene (1).“21 In water,
`the
`fluorescence quenching by methylviologen is less effective by
`a factor of ~50, when compared to similar experiments with
`MPS—PPV. However,
`in the presence of
`the surfactant
`dodecyltrimethylammonium bromide, methylviologen
`is
`more effective at quenching the fluorescence of 1, relative to
`MPS—PPV. Since surfactants are often required to stabilize
`deoxyribonucleic acid (DNA)/protein, protein/protein, and
`DNA/DNA recognition eventsml these results suggest the
`use of discrete molecules such as 1 in the design of fluores—
`cence-based biosensors.
`
`0(CH2)4SO 3M
`
`0(CH2)4803Na
`
`
`
`1
`
`In this contribution, we show the synthesis and character-
`ization of 1,4—bis(9’,9’-bis(6”—(N,N,N-trimethylammonium)-
`hexyl)-2’—fluorenyl)benzene tetraiodide (2) and 1,4-bis(7’-
`(9”,9”—bis(6’”—(N,N,N-trimethylammonium)hexyl)—2”-f1u0re—
`nyl)-9’,9’-bis(6”—(N,N,N—trimethylammonium)hexyl)-2’—f1uore—
`nyl)benzene octaiodide (3). We also examine energy transfer
`processes from 2 and 3 t0 1. P01y(9,9—bis(6’—(N,N,N-trimethyl-
`ammonium)hexyl)-flu0renephenyler1e)
`(4) was prepared to
`provide a comparison against a polymer structure. Together,
`these molecules can be used to examine the chain dependence
`of optical processes in cationic water soluble conjugated poly—
`mersml Additionally, mixtures of 1/2, 1/3, and 1/4 can be used
`to probe the impact of a surfactant on energy transfer pro-
`cesses in aqueous media.
`
`
`
`9
`
`®
`
`le
`
`(9 IO
`
`
`
`Compound 2 is obtained by the sequence of reactions shown
`in Scheme 1. The first step consists of deprotonation of 2-bro—
`mofluorene with NaOH in a two-phase mixture of water and
`1,6—dibromohexane (1:1 ratio). Extraction with dichlorometh-
`ane and distillation of unreacted 1,6-dibromohexane provides
`crude 2-brom0'9,9-bis(6’-bromohexyl)fluorene (5) as a color-
`
`Br(H2C) ;
`
`(CH2)GBr
`
`MeZN(HZC) ,
`
`(CH2)5NM62
`
`0'0 -L *L L “m
`
`5
`
`6
`
`M52N(H20)s
`
`(CH2)6NM82 Me2N(H§).
`
`(CHzleN M92
`
`iii)
`
`ADD . A00 ___.M 2
`
`7
`
`ii) HNMez/THF;
`i) NaOH/HZO/Br(CH2)6Br;
`Scheme 1.
`CfiH4/Pd(dppf)Clz/THF/K2C03; iv) Mel/THF/DMF/HZO.
`
`iii)
`
`l.4-(B(OH)2)2-
`
`less oil. Purification by chromatography provides 5 in 83 0/o
`yield. Addition of dimethylamine to 5[151 in tetrahydrofuran
`(THF) at —15 °C followed by reaction over a 24 h period pro—
`vides 2-bromo—9,9-bis(6’—(N,N—dimethylamino)hexyl)fluorene
`(6) in 97 0/o yield. Coupling two equivalents of 6 with 1,4-phe-
`nyldiboronic acid under Suzuki conditions with Pd(dppf)C12
`(dppf = 1,1’—bis(diphenylphosphino)ferrocene)l16] in refluxing
`THF over 48 h gives, after purification by chromatography,
`1,4-bis(9’,9’-bis(6”—(N,N-dimethylamino)hexyl)—2’-fluorenyl)-
`benzene (7) in 77 % yield. The final step in the synthesis is
`quarternization of the tertiary amines by using methyliodide in
`THF/dimethylformamide (DMF). Water needs to be added
`after a few minutes of reaction to redissolve the reaction mix-
`ture. Compound 2 is purified by precipitation from ethanol.
`The larger chromophore 3 is obtained by a similar set of
`reactions and building blocks to that used for 2, as shown in
`Scheme 2.
`2,7-Dibromo-9,9—bis(6’—(N,N-dimethylamino)hex-
`yl)flu0rene (8) can be generated in 78 0/o overall yield, starting
`with 2,7—dibr0mofluorene by reaction of 1,6—dibrom0hexane
`followed by treatment with dimethylamine. An excess of 8
`was added to 1,4-phenyldiboronic acid under Suzuki condi-
`tions to give 1,4-bis(7’—bromo-9’,9’-bis(6”-(MN—dimethylami-
`no)hexyl)-2’-fluorenyl)benzene (9). Purification by chroma—
`tography is required at this stage to separate 9 from small
`
`362
`
`© WILEY-VCH Verlag GmbH, D-69469 Weinheim, 2002. 0935-9648/02/0503—0362 $ l7.50+.50/0
`
`Adv. Mater. 2002. [4 No. 5, March 4
`
`4
`
`

`

`
`
`
`
`
`
`Me2N(HZC)6
`
`(CH2)6NMe2 Me2N(H2C)6
`
`(CH2)6NM82
`
`
`</
`\> [ / \
`2 _
`'—
`
`.31).
`
`a
`
`2
`
`iii) 1.4—(B(OH)2)2-
`ii) HNMeZ/THF;
`i) NaOH/HZO/Br(CH2)6Br;
`Scheme 2.
`C6H4/Pd(dppf)Clz/THF/KZCO3; iv) nBu—Li/THF; v) 2-isoprop0xy-4.4,5,5-tetra-
`methyl—l,3,2-dioxaborolane/THF: vi) Pd(dppf)Clz/THF/K2CO3; vii) Mel/THF/
`DMF/Hzo.
`
`quantities of oligomeric coupling products. Conversion of
`6 to 2-(9',9’—bis(6”-(N,N—dimethylamino)hexyl)-2’—fluorenyl)—
`4,4,5,5-tetramethyl-1,3,2-dioxaborolane (10) is done via bro—
`mine~lithium exchange using n-butyl
`lithium, followed by
`quenching with 2-isopropoxy-4,4,5,5—tetramethy1-1,3,2-dioxa-
`borolane.[17] The reaction of 9 with two equivalents of 10 pro-
`vides
`1,4—bis(7’-(9”,9”—bis(6’”-(N,N—dimethylamino)hexyl)—2"—
`fluorenyl)-9’,9’-bis(6”—(N,N-dimethylamino)hexyl)-2’-fluore-
`nyl)benzene (11). Quarternization with methyliodide in THF/
`DMF/HZO gives the desired 3.
`The 1H nuclear magnetic resonance (NMR) spectra of 2
`and 3 show broad resonance peaks that are difficult to distin-
`guish at room temperature. However, at 90 °C, the peaks be-
`come sharp, which allows for routine structural assignment.
`All of the methyl signals correspond to quarternized amine
`groups by both 1H and 13C NMR spectroscopy. Further struc-
`tural assignment can be obtained by electrospray mass spec-
`trometry (MS). For example, the electrospray ionisation mass
`spectrum (ESI—MS) of 2 shows data corresponding to
`M(1355.50, 2 — 1'): M(614.31; 2 — 2132+, M(367.25; 2 — 3 r)“,
`M(243.70; 2 — 41’)“, and a fragment M(265.15; 2 — fluorene
`— 21‘)“. Interestingly, in the case of 3, an additional fragmen—
`tation mechanism, involving elimination of methyliodide, was
`observed. Thus, one observes a series of fragments, which
`have lost between one and three units of methyliodide.
`The synthesis of polymer 4 utilizes the same building blocks
`(8 and 1,4-phenyldiboronic acid) and reaction conditions as
`for the synthesis of 9, but using a stoichiometric ratio of the
`two, as shown in Scheme 3. Poly(9,9-bis(6’—(N,N-dimethylami-
`no)hexyl)—fluorenephenylene) is obtained in 47 % yield after
`precipitation from methanol. Structural assignment can be
`achieved by 1H and 13C NMR spectroscopy. Gel permeation
`
`M62N(H
`
`(CH2)6NMe2
`
`,
`
`H
`
`_i___>
`
`C.
`OH
`O O O
`58% }<
`HO
`OH
`Scheme 3. i) Pd(dppf)Clz/THF/K2C03; ii) Mel/THF/DMF/HZO.
`
`ii)
`
`chromatography (GPC) analysis shows a molecular weight of
`Mn 2 8600 g/mol and a polydispersity of 1.9. Quarternization
`of poly(9,9-bis(6’-(MN—dimethylamino)hexyl)-fluorenephenyl-
`ene) with methyliodide in THF/DMF/water gives the desired
`4, as determined by elemental analysis.
`In water the absorption maximum of 2 occurs at 333 nm
`(8333 : 6.6 x 104 Lmol'1 cm’l) and is identical to that observed
`for the neutral precursor 7 in chloroform. In cyclohexane, 7
`shows an absorption maximum at 328 nm. The photolumines—
`cence spectrum of 2 in water, with two maxima at 377 nm and
`397 nm, is nearly identical to that of 7 in chloroform. Thus,
`the chromophore core in 2 shows a negligible solvatochromic
`shift. Comparison against 9,10-diphenylanthracene in cyclo-
`hexane as a standard showed the emission efficiency of 2 in
`water to be 92 i 5 0/0. The spectra of 3 in water show similar
`features to those of 2, except for a 31 nm bathochromic shift
`(labS = 364 nm; 8364 = 1.3 X 105 Lmol’1 cm‘l; lfiu = 408 nm and
`426 nm), brought about by the additional conjugated units.
`Compound 3 displays a fluorescence efficiency of 53 % i 5 "/o.
`Polymer 4 exhibits an absorption maximum at 369 nm
`(8369 = 3.1 x 104 Lmol’l cm‘1 per repeat unit). The photolumi-
`nescence spectrum of 4 in water is broader than the spectra of
`2 and 3 and is centered at 417 nm (labS = 370 nm). Extension
`in repeat units from 3 to 4 therefore does not shift the absorp-
`tion and photoluminescence spectra significantly. The fluores-
`cence efficiency of 4 (32 i 5 0/o) is lower than that of 3, prob—
`ably as a result of functionalities at the ends of the chain and
`additional intrachain self quenching.
`The absorption spectrum of 1 in water overlaps with the
`emission spectra of 2, 3, and 4, thus we would expect effi-
`cient Forster energy transfer between these molecules.[18‘19]
`Indeed, when 1 is added to a solution of 2, one observes a
`decrease in the emission of 2, with a concomitant increase
`in the emission of 1 (Fig. 1). For the spectra shown in
`Figure 1, [2] = 2 x 104‘ M, while [1] varies in the range from
`
`1.4x1o‘
`
`1.2x1o6
`
`1.0x1o‘
`
`8.0x105
`5
`
`6.0x10
`
`4.0x1o5
`
`PL[cps]
`
`2.0x1o5 0.0 A ‘
`
`350
`
`400
`
`500
`450
`Wavelength [nm]
`
`550
`
`600
`
`Fig. 1. Fluorescence spectra obtained by addition of 1 to 2. Conditions: [2] =
`x 10* M. [1] : 0 to 0.8 X 10*) M; 2m = 340 nm.
`
`Adv. Mater: 2002. 14. No. 5. March 4
`
`© WILEYVCH Verlag GmbH. D-69469 Weinheim, 2002
`5
`
`09359648/02/0503—0363 $ 17.50+.50/0
`
`363
`
`5
`
`

`

`
`
`8 x 10'8 M to 1 x 10'6 M. The overall emission intensity in
`these mixtures decreases, consistent with the lower fluores-
`
`cence efficiency of 1 (10 i 5 %), relative to 2. Mixtures of 1
`and 3 yield spectra similar to those shown in Figure 1.
`Stern—Volmer analysis gives insight into the efficiency of
`the energy transfer process according to the equation:
`
`—Q=1+stlQl
`
`(1)
`
`A plot of PLO/PL versus [1], with [2] = 2 x 10* M is showu
`in Figure 2 (PLO refers to the overall integrated emission in
`the absence of 1, PL corresponds to the intensity in the pres—
`ence of 1).”01 From the slope of these linear plots one obtains
`the Stern—Volmer constant, KSV. which provides a measure of
`
`3.0
`
`2.5
`
`in 2.0
`°-‘
`a 1‘5
`1.0
`
`40
`
`35
`so
`
`25
`
`.l
`g 20
`d 15
`1o
`
`
`
`K3v=3.17E+06 M"
`
`°
`
`1x1o"2x1o"3x10"4x10‘75x10"6x1o"
`[111M]
`
`I
`
`I
`
`
`
`a.ox1o"
`
`1.ox1o‘
`
`
`6.0x1o"
`°~°
`2.0x10"
`4.ox1o"
`[HIM]
`
`Fig. 2. Stern—Volmer plot of the quenching efficiency. Fluorescence data ob
`tained from spectra in Figure l for [2] = 2.0 X 10'6 M. [1] = 0—0.8 x 10'“ M: A.“
`= 340 nm.
`
`the rate for quenching or energy transfer. The Stern—Volmer
`plot in Figure 2 is typical for those obtained with mixtures of
`1 and 2, as well as 1/3 and 1/4. A linear region is observed at
`low quencher concentrations, followed by an up-sloping non-
`linear (“superlinear”) region where the energy transfer may
`be best described by a “sphere-of—action” mechanismlzml
`Similar behavior of PLO/PL versus fluorescence quencher is
`observed with anionic conjugated polymers and cationic
`quenchers such as methylviologen.[22]
`The linear region of Figure 2 provides a KSV value of
`3.2 x 10" M'l. Using the fluorescence lifetime of a chromo-
`phore similar to 2,931 one 'can provide a conservative estimate
`for the fluorescence lifetime of 2 to be 0.7 ns. Assuming a
`
`dynamic quenching mechanism, one would estimate the
`dynamic quenching rate constant to be kq = KSV/rf ~ 4.6 x
`1016 M’1 s'l, which is several orders of magnitude above values
`for diffusion—controlled quenchingml Static quenching by
`formation of ground state complexes therefore dominates and
`is favored by the Coulombic stabilization by ion pairing
`between 1 and 2.
`
`As the concentration of the cationic chromophore de—
`creases,
`the magnitude of the KSV value for fluorescence
`quenching with 1 increases significantly. Figure 3 compares
`this effect for both 2 and 3, as a function of fluorene repeat
`
`unit (RU). Note that at [2] = 1 x 10‘8 M, KSV approaches val-
`
`1.0x1oll
`
`1.0m7 A
`
`A
`
`o
`
`a—
`
`3
`
`1.0x10“
`
`6
`
`A
`
`A
`
`A
`6
`
`8
`o
`1.0X105'—’1'i—'I'—t"i‘i"_1
`.wi
`0
`1x10" 2x10" 3x10" 4x10" 5x10" 6x10" 1x10" 8x105 9x10"
`[RU]["|°|/L]
`
`
`Fig. 3. Effect of donor concentration on the energy transfer efficiency from 2
`
`
`
`(
`). 3 (O). and4 (A) to 1.
`
`ues of 1 x 108 M‘l, which reflects very efficient fluorescence
`quenching.[8“z‘”l Under these circumstances, the presence of
`10'9 M 1 causes a 20% drop in emission intensity. which is
`easily detected using standard instrumentation. It is also sig—
`nificant that. within experimental certainty,
`the st/repeat
`unit values for 2 and 3 are identical.
`
`To understand the increase in quenching efficiency as a
`function of concentration we consider a molecule of 2 in solu—
`
`tion. A greater entropic driving force exists at lower concen-
`trations for the dissociation of iodide ions away from the posi-
`
`tively charged oligomer. This removal of ions decreases
`electrostatic screening around 2 and favors close proximity
`between 1 and 2. Similar arguments apply for the larger KSV
`values observed for 3 and 4 at low concentrations.
`
`Figure 3 also shows st values obtained for energy transfer
`between the polymer 4 and 1. These values are ~3—4 times
`larger than those observed with 2 and 3. Fluorescence quench-
`ing of MPS-PPV is also greater than that of the oligomeric
`counterpart 1112] Intermolecular and/or intramolecular energy
`transfer processes between oligophenylene units in the poly-
`mer chain must take place and the larger st reflects the
`macromolecular aspect of 4114]
`As mentioned earlier, molecules with surfactant properties
`
`are often present in buffers that stabilize biochemical recogni-
`tion eventsml Addition of sodium dodecylsulfate (SDS) to 2.
`3, and 4 causes a broadening of the absorption spectra and a
`reduction in the optical density. The 8 values at the absorption
`maximum are decreased by a factor of three. The emission
`efficiency under these conditions changes slightly (:10%),
`once the drop in absorption is taken into account. Figure 4
`summarizes the effect of [SDS] on the st for energy transfer
`to 1. Correlating the ratio of SDS equivalents against
`the
`number of charge units (CU) allows a straightforward com-
`parison as a function of molecular structure.
`Two distinct regions for the three chromophores can be
`observed in Figure 4. In the range 0 ——> 0.75 [SDS]/[CU] there
`is little change in the KSV values for 2 and 3. but a decrease
`occurs with polymer 4. Interestingly, at [SDS]/[CU] = 0.75, the
`st values for the three cationic species are very close in
`magnitude. Increasing [SDS]/[CU] after this point reveals no-
`ticeable differences as function of structure. In the case of 2,
`
`st increases slightly in the l —> 2 [SDS]/[CU] range. and
`
`364
`
`© WILEY-VCH Verlag GmbH, D-694o9 Weinheim, 20026 0935-9648/02/0503-0364 $ 1750+.50/0
`
`Adi: Mater. 2002.14.No.5. March 4
`
`6
`
`

`

`
`
`
`
`ADVANCED .—
`MATERIA S
`
`5x10
`
`4x10’
`
`1x10’
`
`Kym") 2x10
`
`[snsi / [CU]
`
`Fig. 4. Effect of SDS concentration on: a) st for 2/1: b) Ksy for 3/1: C) st for
`4/1: in all cases [CU] = 4.0 x 10'6 M.
`
`then decreases, ultimately reaching a value similar to that ob-
`served in the absence of surfactant. A more pronounced in-
`crease in KSV occurs for 3, at [SDS]/[CU] = 1, KSV : 4 x
`107 M“. A decrease follows and when [SDS]/[CU] = 5, Le.
`40 equivalents of SDS relative to 3, the KSV is substantially
`higher than in the absence of surfactant. Finally. for the larg-
`est molecule 4, the increase in st is the largest (from 5 x
`106 M‘1 to 5.2 x 107 M‘l) and no decrease in magnitude is ob—
`served at [SDS]/[CU] = 5.
`Maximum sensitivity for the energy transfer to 1 is thus ob—
`tained for the polymer 4 in the presence of a large excess of
`surfactant. The data in Figure 4 reveal how sensitive the effi—
`ciency of this process is to the number of repeat units in the
`donor chromophore. We suspect that quenching efficiencies
`depend on the aggregation of the chromophores in water and
`to the extent to which these supramolecular structures influ—
`ence electronic coupling between optical subunits and the
`average donor/acceptor distance. It is also interesting to note
`that the fluorescence quenching of MPS—PPV with methylvio-
`logen decreases in the presence of the surfactant dodecyltri—
`methylammoniumbromide (DTA). A similar trend occurs for
`1/4 at [SDS]/[CU] < 0.75. However, with MPS—PPV and DTA
`precipitation occurs at [DTA]/[CU] = 1. This system cannot
`access the regime of efficient quenching with additional sur-
`factant, as in SDS with 4.
`
`The synthesis and optical studies of 2, 3, and 4 provide a
`framework for future work with conjugated water soluble
`polymers and their respective oligomeric counterparts. Design
`of new optical platforms will require balancing the properties
`of size with the corresponding solvent environment. The
`smaller chromophores have larger quantum yields and are less
`sensitive by solvent media, yet show lower quenching efficien—
`cies, or sensitivity, when compared to their larger counter-
`parts.
`
`dried over MgSO... and concentrated. The residue was purified by silica gel col-
`umn chromatography (methanol/ethyl acetate/hexane/ammonia 10:88:10:2) to
`give 7 (0.39 g. 77 %). 1H NMR (CDCl;) (5 [ppm]: 0.7 (m. 8H). 1.1 (m. 16H). 1.3
`(m. 8H). 1.8—2.2 (m. 40H). 7.3—7.8 (m. 18H): I3C NMR (CDCIJ) () [ppm]: 24.2.
`27.5. 27.9. 30.3. 40.75. 45.9. 55.5. 60.1. 120.2, 120.4. 121.8. 123.3. 126.2, 127.3.
`127.5. 127.8. 139.9. 140.8. 140.9. 141.1. 151.3. 151.7: MS (electron impact MS.
`EI-MS): 915 (M + H1). 787 (M — ClegN').
`1.4-315(9’.9’-bis(6"-(N.N.N-trimeihylammonium)hexy/)-2’-flm)renyl)benzene
`Terra/odide (2): Methyl iodide (0.70 g. 4.93 mmol) was added to 7 (100 mg.
`0.109 mmol) in 4 mLTHF and 1 mL DMF at room temperature (RT). Precipi-
`tation was observed after 1 min of stirring. The solution was made homoge-
`nous by addition of 1 mL H20. After 24 h, the mixture was dried in vacuum.
`The residue was recrystallized from 10 mL ethanol to yield 2 (80 mg. 49 %).
`1H NMR (D20. 90 °C) (5 [ppm]: 0.6417 (m. 8H). 0.9—1.0 (m. 16H), 1.4 (m. 8H).
`1.9~2.0 (m. 8H). 3.0—3.1 (m. 44H). 7.5 (m. 48). 7677.7 (m. 4H). 7.9—8.0 (6H):
`13C NMR (D30. 90 °C) 6 [ppm]: 232. 24.5. 26.1, 29.4. 39.9. 54.4. 56.3. 67.8.
`121.0. 121.7, 121.9. 125.1. 126.7. 128.4. 128.5 (2C). 128.8, 139.2. 140.3. 141.3.
`141.5. 152.5, 153.1: MS (ELMS): 367 (M — 313*). 243 (M — 414*). Elemental
`analysis calculated for C68H10214N4: C, 55.07; H, 6.93; N. 3.78; found: C, 54.99:
`H. 6.96: N. 3.82.
`I,4-Bis(7’-(9”.9”»bis(6’”-(N.N-dimethylamin0)hexyl)-2”-f/iiureny/)-9’.9’-
`bi‘s(6”-(N.N-dimethylamino)hexyl)-2’-fliwrenyl)benzene (II): A mixture
`of 10 (0.24 g. 0.44 mmol), 9 (0.20 g, 0.19 mmol), PdC12(dppf) (6 mg. 7.35 x
`10’“ mol). and K2C03 (0.51 g, 3.7 mmol) in 4 mL THF and 2 mL water
`was degassed and stirred at 80 °C for 68 h. The mixture was extracted with
`CHC13. The organic layer was washed with water and brine. dried over
`MgSO4 and concentrated. The residue was purified by silica gel column
`chromatography (CHClg/hexane/triethylamine 5:5:1 to 9:1:1) to give 11
`(0.21 g. 64 %). 1H NMR (CDC13) 6 [ppm]: 0.6—1.0 (m, 16H). 1.1 (m, 32H),
`1.3—1.5 (m, 16H). 2.1 (m,16H), 2.3—2.4 (m, 64H). 7.3—7.4 (m, 10H), 7.6—7.9
`(m. 20H):13C NMR (CDC13) 6 [ppm]: 24.1, 24.2. 26.8, 26.9. 27.2 (2C). 30.1.
`30.2. 40.7 (2C), 44.9, 45.0. 55.5. 55.7, 59.5, 59.6. 120.2. 120.4. 120.5, 120.6.
`121.6. 121.6. 121.8, 123.3. 126.4, 126.5, 126.7. 127.3. 127.5. 128.0. 139.9.
`140.4. 140.6. 140.7, 140.8 (2C), 140.9. 141.1,151.1,151.7. 151.9. 152.0: M