Fluorescent MolecularDevicesDOI: 10.1002/anie.200702070The Chemistry of Fluorescent Bodipy Dyes: VersatilityUnsurpassed**Gilles Ulrich, Raymond Ziessel,* and Anthony HarrimanIn memory of Charles Mioskowski Bodipy dyes/pigments energy transfer fluorescent probes luminescence1. IntroductionDespiteexistingfor almost acentury, fluorescent dyescontinuetoattracttheattentionofscientistsfromanever-expandingmultidisciplinaryarena. Recentdevelopmentsinthefieldofpersonaldiagnosticsandintheareaoforganicelectroluminescent devices have boosted interest in thedevelopment of next-generation emissive dyes. Countlessclasses of highly fluorescent organic compounds are nowknown, but the difluoro-boraindacene family (4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene, abbreviated hereafter asF-Bodipy)hasgainedrecognitionasbeingoneofthemoreversatile fluorophores and this dye has steadily increased inpopularity over the past two decades. The first member of thisclassof compoundwasreportedbyTreibsandKreuzerin1968,[1]althoughrelativelylittleattentionwasgiventothediscovery until the end of the 1980s.[2]Then, the potential useof this dye for biological labeling was recognized[3]and severalnew Bodipy[4]-based dyes were designed and indeed commer-cializedfor biological labeling. As aconsequence, Bodipy came to beknown to the biochemist and biologistas a photostable substitute for fluores-cein, andthenumber of papers andpatentsstartedtoescalateinthemid1990s (Figure 1). The use of Bodipy as an effective biologicallabel has beencomplementedbyits knownpropensitytofunction as a tunable laser dye.[5]At the beginning of the 21stcentury, numerous patents were deposited for additionalbiological labelingpurposes, forpaint orinkcompositions,and for electroluminescent devices. In parallel, more funda-mental studies onthechemical reactivity andthe photo-physical propertiesofthenewdyesbegantoemerge. Thisworkhas brought about a further rise inthe number ofpatents and research publications attesting to the versatility ofthe Bodipy classof fluorophores; in 2006, some 729 patentsand1074 journal articleswerepublishedthatdescribedthemultifarious applications of Bodipy-based dyes.[6]The excel-lentthermal andphotochemical stability, highfluorescencequantumyield, negligible triplet-state formation, intenseThe world of organic luminophores has been confined for a long timeto fairly standard biological labeling applications and to certainanalytical tests. Recently, however, the field has undergone a majorchange of direction, driven by the dual needs to develop novel organicelectronic materials and to fuel the rapidly emerging nanotechnologies.Among the many diverse fluorescent molecules, the Bodipy family,first developed as luminescent tags and laser dyes, has become acornerstone for these new applications. The near future looksextremely bright for porphyrins little sister.Figure 1. Annual number of scientific publications describing Bodipyfluorophores (source: CAS).[*] Dr. G. Ulrich, Dr. R. ZiesselLCM, ECPM, UMR 7509CNRS-Universit Louis Pasteur25 rue Becquerel, 67087 Strasbourg Cedex 02 (France)Fax: (+33) 3-9024-2689E-mail: ziessel@chimie.u-strasbg.frProf. Dr. A. HarrimanMolecular Photonics LaboratorySchool of Natural SciencesBedson Building, University of NewcastleNewcastle upon Tyne, NE1 7RU (UK)[**] Bodipy, deriving from borondipyrromethene, denotes dipyrrome-theneboron difluoride, 4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene.R. Ziessel et al. Minireviews11842008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2008, 47, 1184 1201absorptionprofile, goodsolubility, andchemicalrobustnesshave all added to the general attractiveness of these materials.2. Synthetic ConsiderationsThecomplexationofadipyrrometheneunittoaborontrifluoridesaltcanleadtoformationofadipyrromethene-boron difluoride structure, which can be considered as beingan example of a rigidified monomethine cyanine dye(Figure 2). The greatly restricted flexibility leads to unusuallyhigh fluorescence yields fromthe dipyrrometheneboronframework. Conjugationof thep-electrons runs alongtheorganicbackboneandcanbeextendedbycondensationofsuitablegroupsontotheperipheryorbytheattachmentofconjugated units to one or both pyrrole fragments.Thistype ofstructure is commonly describedasbeingaboradiazaindacenebyanalogywiththeall-carbontricyclicring, and the numbering of any substituents follows rules setup for the carbon polycycle (Figure 3). By analogy withporphyrinicsystems, the8-positionis oftenreferredtoasbeing the meso site. The recent development of non-fluorinated Bodipy dyes led to the introduction of a supple-mentary term for the Bodipy abbreviation that is specific withrespect tothenatureof the4,4-substituents: F forfluoro;C for carbocycle, E for ethynyl, and O for oxygen. Theabsorption- and fluorescence-spectroscopic properties ofmembersoftheBodipyfamilyare highlyinfluencedbytheextent of electron delocalization around the central cyanineframework and, in a modest way, by the donor and acceptorcharacteristics of the pyrrole substituents. It is, in fact, quiterare for Bodipy dyes to lack alkyl substituents at the pyrrolegroups.2.1. Basic ProcedureConstruction of the starting dipyrromethene unit is basedon the well-known pyrrole condensation reaction, developedoriginallyforthesynthesisofcertaintypesofporphyrin. Ahighlyelectrophiliccarbonyl compound(forexample, acidanhydride, acyl chloride, oraldehyde)isusedtoformthemethenebridgebetweentwopyrroleunits. Thelatter areusuallysubstitutedat oneof thepositions adjacent tothenitrogen atomto avoid polymerization and/or porphyrinformation. An excess of a non-substituted pyrrole is needed toobtainsatisfactoryyieldsofthecorrespondingnakeddipyr-romethene.[7, 8]Such synthetic procedures rapidly lead to theisolation of symmetric F-Bodipy dyes after complexation ofBF3OEt2in the presence of a base, such as a tertiaryamine,[5, 9]as shown in Scheme 1.Using this synthetic method, numerous Bodipy units havebeen built from readily available pyrroles, with the syntheticeffort beingfocusedonvaryingthenatureof substituentslocatedatthe8-position.[1012]Thisstrategyhasallowedtheconnection of selective groups directly onto the Bodipyfluorophore without drastic change of their optical properties.Such approaches do not perturb the geometry of theGilles Ulrich was born in Strasbourg(France) in 1970. He received his PhDdegree from Dr. R. Ziessel (1996) forresearch related to stable nitroxyl radicalsand to luminescent lanthanide complexes.After post-doctoral research stays with Prof.H. Iwamura (University of Kyushu, Japan),Dr. J. J. Wolff (Universitt Heidelberg, Ger-many), and Dr. F. Arnaud-Neu (ULPStrasbourg), he joined the CNRS in 1999 atUniversit Paul Sabatier, Toulouse (France).He rejoined R. Ziessel in 2002. His researchinterests include the development of neworganic functional fluorophores based onBodipy dyes.Raymond Ziessel is the Director of theLaboratoire de Recherche en Chimie Mo-lculaire at the Engineer School ofChemistry (ECPM) in Strasbourg. Recentresearch interests focus on the use oncarbon nanostructures loaded with size-con-trolled clusters for the vectorization ofmicrowaves and heterogeneous catalysis andalso in the use of confined nanocrystals forenergy conversion devices. He has publishedover 350 papers in journals and mono-graphs, and is co-author of 10 PCT patents.Anthony Harriman was at the Royal Institu-tion (UK) for 14 years, where he was DewarResearch Fellow and Assistant Director ofthe DavyFaraday Research Laboratory. Hemoved to the University of Texas at Austinin 1988 to become Director of the Centerfor Fast Kinetics Research (CFKR). He thenwent to the Department of Chemistry atthe University of Newcastle (1999). Hisresearch interests include aspects ofbiophysics, especially electronic interactionsin DNA. His work is moving towards theemerging field of molecular photoelectronics.He has published more than 350 researcharticles.Figure 2. Basic types of cyanine structure.Figure 3. Numbering scheme used for the Bodipy framework derivedfrom indacene.Bodipy DyesAngewandteChemie1185 Angew. Chem. Int. Ed. 2008, 47, 1184 12012008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.angewandte.orgchromophore, they tend to avoid problems arising from sterichindrance, andhavelittletendencytomodifytheelectrondensity onthe Bodipy unit. Akey point is that pyrrolesubstituentsrestrictrotationofaromaticgroupsattachedatthe 8-position and the resultant orthogonal geometry servestominimizeelectronic couplingbetweenthedyeandthemesosubstituent. Manyinterestingchemical sensors havebeen formulated in this way (see Section 4), which continuesto be the most popular route to functionalized Bodipy dyes.AsymmetricBodipydyes areusuallyobtainedbycon-densationof acarbonyl-containingpyrrolewithapyrrolemolecule that is not substituted at the 2-position. ManyBodipy-based biological labels[3, 4]are prepared by thisparticularmethod(Scheme 2). Anactivecarboxylategroupcanbeintroducedat the8-positionbyfollowingasimilarprocedure. This synthetic route is useful for the preparation ofreasonably large batches of dyestuff, although it tends to beexpensiveinterms of solvent wastage. Purificationis bestcarriedoutbycolumnchromatographyfollowedbyrecrys-tallization. Ingeneral, thesematerials separatewell onachromatography column and can be purified to a high degree.2.2. Chemistry on the Bodipy Core2.2.1 Electrophilic SubstitutionTreibs andKreuzer[1]first realizedthat F-Bodipydyeswhicharefreeof substituents at the2,6-positions readilyundergo electrophilic substitution reactions in the presence ofchlorosulfonic acid. This high level of reactivity was exploitedlater by Boyer and co-workers as a means by which tosynthesize water-soluble analogues.[13]Other electrophiles canbeintroducedinmuchthesameway, therebyprovidingafacile route to the isolation of F-Bodipy dyes bearingbromine[14]or iodinegroups[15]that arethenavailableforfurther synthetic modification (Scheme 3). It should be notedthat this approach leaves the BFbonds unscathed; thesubstitutionreactionsoccurexclusivelyatthe2,6-positions,and is therefore a valuable route to selective substitution.2.2.2 Active Methyl GroupsAn F-Bodipy core bearing methyl groups at the 3,5-positions can be subjected to chemical modifications on themethyl carbon atoms owing to their strong nucleophiliccharacter. Thesemethylgroupscanbedeprotonatedundermild conditions. The resultant intermediates will readily addtoanelectron-richaromaticaldehyde,therebygeneratingastyrylgroup(Scheme 4).[3, 16, 17]Thissyntheticprocedurehasbeen used to extend the degree of p-electron conjugation andhas the effect of introducing a pronounced bathochromic shifttobothabsorptionandfluorescencespectral maxima. Fur-thermore, theintermediarycarbeniumioncanbeoxidizedin situ, leadingtothecorresponding3-formyl derivativeinquite respectable yield.[17]Scheme 1. Outline of a typical synthesis of symmetric F-Bodipy dyes.The base removes HF formed in the final step.Scheme 2. General outline for the synthesis of asymmetric F-Bodipydyes.Scheme 3. General procedure leading to electrophilic substitution atthe F-Bodipy unit. a) Electrophile in anhydrous solvent.Scheme 4. Introduction of styryl groups by additionelimination stepswith an adventitious aldehyde. Ac=acetyl.R. Ziessel et al. Minireviews1186 www.angewandte.org2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2008, 47, 1184 12012.2.3 Metal-Catalyzed Cross-CouplingThepresenceofahalogenatom, eitherdirectlyontheBodipycoreorattachedtoanaryl ring, facilitatesfurtherextension of the conjugation length and the building of moresophisticatedstructuresthroughtheuseof palladium-cata-lyzedcouplingreactions.[18]Ahalogenatomcanbeintro-duced onto the F-Bodipy core by way of a suitably substitutedpyrrole,[19]with chlorinated dipyrromethene precursors,[20]orby electrophilic substitution onto the Bodipy unit.[12]Varioustypes of coupling reactions, such as Sonogashira, Heck, Stille,or Suzuki, have been used to introduceethyne, ethene, andaryl groups onto the F-Bodipy framework (Scheme 5). Again,itshouldbenotedthattheBFbondsremaininertduringsuch cross-coupling reactions.Therational designof F-Bodipydyes startingfrom4-iodobenzoylchloride[21]leads to fluorescent materials that canbe easily connected to certain aryl or heteroaryl groupsthrough similar palladium(0)-catalyzed procedures. Thismethodispreferredforassemblingmulticomponentmolec-ular systems capable of intramolecular energy and/or electrontransfer (see Section 3.1).2.2.4 Nucleophilic Substitution of Leaving GroupsThepresenceof goodleavinggroups, suchas chlorineatoms at the3,5-positions of anF-Bodipydye, allows thefacile introduction of amino or alkoxy groups at these sites bynucleophilicsubstitution (Scheme 6).[22]Athiomethyl groupat the8-positionis alsoaneffectiveleavinggroupinthepresence of an amine.[23]2.3 Extending the Degree of p-Electron ConjugationObtainingF-Bodipydyesexhibitingfluorescenceinthefar-red or near-IRregions of the spectrumrequires thepresence of an extended delocalization pathway. Severalstrategies are available by which to build this type of Bodipydye. The most direct method is to synthesize pyrrolederivatives bearing phenyl, vinyl, or thiophene groups at the3-position (Figure 4).[24, 25]Derivatives with an additional benzene ring fused to thepyrrole group are well known and can be used as the basis ofan alternative strategy for the introduction of a bathochromicshift (Figure 5), but it should be noted that isoindoles are notsuitablefor thestrategydescribedinScheme 1. However,Urano et al. showed[26a]that the isoindole framework could beunmasked by a retro-DielsAlder reaction (Scheme 7). Thisprocedureprovides anindirect routetofunctionalizedF-Bodipy dyes starting from isoindole fragments.Related dyes can be obtained by condensation of ortho-diacetophenone with an ammonium salt,followed by boroncomplexation (Scheme 8).[27]A different strategy employed toproduce long-wavelength absorbing Bodipy-based dyes is tochemicallymodifytheBodipyframework(Figure 5). Onesuch way to extend p-electron delocalization is by formationof astyryl groupat the3-positionof theBodipyunit byreaction of a methyl group with an active aldehyde in basicmedia. Conversely, a Wittig-type reaction can be carried outon a suitable aldehyde.[13]This latter strategy has been usedrecently with considerable success to generate a new class ofratiometric fluorescence sensors (see Section 4).Scheme 5. Examples of palladium-catalyzed cross-coupling reactionson the F-Bodipy core. a) Reagents: SnPh4 (R=Ph), or ClC6H4B(OH)2(R=p-ClC6H4), or styrene (R=CHCHPh), or phenylacetylene(R=CCPh).Scheme 6. Selected example of nucleophilic substitution at the 3,5-position of an F-Bodipy dye.Figure 4. Examples of F-Bodipy dyes with extended p systems.Figure 5. F-Bodipy dyes with a bis(isoindole)methene core.Bodipy DyesAngewandteChemie1187 Angew. Chem. Int. Ed. 2008, 47, 1184 12012008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.angewandte.org2.4. Modifications at the Boron CenterFew attempts had been reported that set out to substitutethefluorineatomsof anF-Bodipydyeuntil veryrecently,when Murase et al. registered a patent[28]reporting thereplacementofthefluorineatomswitharyl groups. Inthiscase, phenylmagnesiumchloridewasusedtocarryout thereplacement. The organometallic approach has been furtherdeveloped by Ulrich, Ziessel, and co-workers[29]and used tointroducearyl,[30]ethynylaryl,[31]andethynyl[32]subunits inplace of the usual fluorine atoms. These developmentsprovidedaccesstoalibraryofhighlystableC-BodipyandE-Bodipy dyes and opened the way to the preparation of newdiads and cascade-type dyes. Depending on the nature of thesubstrate,organolithiumorGrignardreagentswereusedtoefficiently substitute the fluorine atoms (Scheme 9). Theproperties and photophysical behavior of these new dyes willbe discussed in Section 3. It should be stressed, however, thatthissimplestrategyofcarryingoutsubstitution reactionsatthe boron center has led to a dramatic increase in theversatility of Bodipy dyes. In particular, it is now possible tosynthesizesophisticatedarrays inwhichdifferent types ofappended groups are positioned at the meso and boron sites.This approach allows the isolation of molecular triads, tetrads,and so on that were hitherto unimaginable.The first reported example of an O-Bodipy dye involveddisplacement of thefluorineatomswitho-phenoxygroupslocated at the 3,5-positions in the presence of BBr3.[33]Hiroyuki et al. referred to fluorine displacement using sodiumalkoxides (Scheme 9) or thiolates in a patent.[34]This proce-dure was used recently to finetune the reduction potentials offluorescent sensorsfor nitricoxide detection.[35]Itis also ofnote that the fluorine atoms can be rather easily replaced withhydroxy groups in the presence of a strong Lewis acid.[36]2.5. Related StructuresVery recently, interest has been increased in the 4-bora-3a,4a,8-triazaindacene dyes (commonly referred to as azabo-dipy dyes) owing to their efficient fluorescence in the far-redand near-IR regions of the spectrum. The nitrogen lone pair atthe 8-position appears to contribute to the orbital levels of theactual cyanine framework, reducing the HOMOLUMOenergygaprelativetoF-Bodipydyes bearingsimilar sub-stituents. Electrochemical measurements andmolecular-or-bitalcalculationscouldconfirmthiseffect,which isrespon-sible for the red-shifted absorption and emission maxima. Toobtainazabodipydyes, themainsyntheticeffort has beendirected towards isolation of the azadipyrromethene precur-sor, with the boron center being coordinated to fluorine atomsin the usual way. This type of structure was first reported byBoyerandMorgan[37]whoobtainedtheazadipyrrometheneprecursor by condensation of hydroxylamine with 1-oxopro-pionitrile[38]followed by BF3OEt2 complexation. The neces-sary research to obtain symmetric and asymmetric azabodipydyeswasconductedprimarilybythegroupsofOSheaandCarreira, motivated by the potential applications as biologicallabels, as sensitizers for photodynamic therapy,[39]and asluminescent proton sensors.[40]Scheme 7. Retro-DielsAlder reaction used to extend the conjugationfor an F-Bodipy dye. Conditions: a) trifluoroacetic acid, 4,5-dichloro-3,6-dioxo-1,2-benzenedinitrile (DDQ), iPr2NEt, BF3OEt2 in CH2Cl2;b) 2208C, 30 min.Scheme 8. Synthesis of bis(isoindole)metheneboron derivatives fromtwo equivalents of ortho-diacetylbenzene. See ref. [27] for details.Scheme 9. Selected methods for modification at the boron center.TMS=trimethylsilyl.R. Ziessel et al. Minireviews1188 www.angewandte.org2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2008, 47, 1184 1201OSheas method is based on the addition of nitromethaneto a chalcone, followed by condensation with an ammoniumsalt (Scheme 10).[41]In contrast, Carreira and Zhaos restrict-ed azabodipy dyes were obtained by reaction of a 2,4-diarylpyrrole with NaNO2 in an acetic acid/anhydride mixture(Scheme 11).[42]In both cases, the F-azabodipy dye is obtainedby complexation of BF3OEt2 in the presence of Hnigs base(N,N-diisopropylethylamine).3. Optical Properties: Energy TransferOne of the features of Bodipy dyes is that it is possible toeasily modify their molecular backbone, which providesfurtheropportunitiestovarytheiroptical propertiesandtoprovide recognition sites for a variety of analytes. These dyeshave sharp bands in the absorption spectra (half-widthstypically beingaround2535 nm), large molar absorptioncoefficients (typically being in the region of 40000 to110000m1cm1), high fluorescence quantum yields (normal-ly between 60 and 90%), reasonably long excited singlet-statelifetimes (these being around 1 to 10 ns), excellent chemicaland photochemical stability in both solution and solid states,and versatile charge-transfer properties. The good solubilityof thesedyes inmost commonsolvents (excludingwater)shouldalsobenoted. Ingeneral, Bodipydyesareresistanttowards aggregation in solution. The absorption spectrarecorded in solution or plastic films exhibit intense transitionsthat correspondtothe S0S1process, together withclearvibrational fine structure, and a more modest set of transitionsowingtoabsorptionfromS0toS2states. Bothtransitionsusually show vibrational fine structure ranging from 1200 to1400 cm1typical of themolecularC=Cframeworkof theBodipy core. When excited into either S1 or S2 states, strongfluorescence is observed from the S1 state, which shows goodmirror symmetry with the lowest-energy absorption band. Nofluorescence has beenobservedfromthe S2state anditappears that internal conversion is quantitative. For selectedspectroscopic data, see Table 1.Under most experimental conditions, the fluorescencedecay profiles are well described by monoexponential kinet-ics. Ingeneral, theradiativerateconstants(ca. 108s1)arequite high, owing to the strong absorption transitions, whilstthe rate constants (ca. 106s1) for intersystem crossing to thetriplet statearerelativelyunimportant. Theradiativeratescalculated fromthe StricklerBerg expression remain inexcellent agreement with the experimental values. Theexcited triplet state can be detected by laser flash photolysistechniques, and has a lifetime on the order of several ms in theabsence of molecular oxygen. There is only one report of low-temperaturephosphorescencefromasimpleBodipydye,[43]for whichthe process requiredpromotionof intersystemcrossing by the external heavy-atomeffect. Interestingly,triplet emission is also observed for a Bodipy dye equippedwithanancillaryruthenium(II) poly(pyridine) complex,[44]whichfunctionsasatriplet sensitizer. Inbothcases, phos-phorescence is found around 780 nm, which indicates a ratherlow-lying triplet state.3.1. CassettesAcommonproblemfoundwithorganicdyesisthat theStokes shift is too small for optimum use in flow cytometryand fluorescence microscopy. Synthetic strategies have beendeveloped to circumvent this problem by covalent attachmentofanancillarylightabsorbertotheBodipycoretoformacassette. The intention is to channel all the photons absorbedby the secondary chromophore, which is usually an aromaticpolycycle, to the Bodipy emitter. In this way, there is a largedisparity in excitation and emission wavelengths and the fullbenefits of the Bodipy emitter are retained.[19, 45]Someprototypic examples of such dual chromophore dyes aregiveninFigures 6and 7.[46, 47]An importantfeatureofthesesystemsisthatthetwochromophoresremainelectronicallyisolatedbecauseoftheorthogonalarrangementaroundtheconnectinglinkage. Therateofenergytransferdependsonthe structure of the dual-dye systemand decreases withincreasingcenter-to-centerseparationinlinewithadipoledipole transfer mechanism. The overall energy-transferefficiency exceeds 90%, even in the most extended system.[45]Significantly faster energy transfer is found when theanthracene donor is attached to the long axis of the F-Bodipyacceptor,asin 18,thanifthedonoriscoupledtotheshortaxis, as in 17.[19]Some new dual chromophore dyes are given in Figure 7.In each case, the aromatic polycycle, either pyrene, perylene,or a mixture of both, is attached to the boron atom. WhereasScheme 10. Synthesis of an azabodipy dye. Conditions: a) CH3NO2,HNEt2, MeOH, D; b) NH4OAc (Ac=acetyl); c) BF3OEt2, Hnigs base,RT.Scheme 11. Alternative synthesis of a restricted azabodipy dye. Con-ditions: a) HOAc, Ac2O, NaNO2 b) BF3OEt2, Hnigs base, RT.Bodipy DyesAngewandteChemie1189 Angew. Chem. Int. Ed. 2008, 47, 1184 12012008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.angewandte.orgtheabsorptionspectralprofilescontainimportantcontribu-tionsfromeachofthesubunits, fluorescenceoccursexclu-sively from the Bodipy fragment.[47]Intramolecular excitationenergy transfer is extremely efficient in each case, eventhough spectral overlap integrals for the pyrene-based systemare modest. Although sterically congested, molecular dynam-Table 1: Spectroscopic data for selected Bodipy dyes.Compound Solvent labs/nm(e/104m1cm1)lem/nm F/% t/ns E/ V vs SCEB/BCBC+/B1[13]EtOH 493 (7.9) 519 99 7[24]CHCl3/MeOH 546 564 19 8[24]CHCl3/MeOH 588 617 40 9[24]CHCl3/MeOH 637 652 48 10[26]Hexane 529 544 90 5.96 1.57 +0.6711[26]Hexane 599 605 91 5.71 1.53 +0.3312[27]CH2Cl2571 597 13[27]MeOH 634 (10.8) 658 92 14[27]MeOH 766 (6.5) 831 15[41]CHCl3688 (8.5) 715 36 16[42]CH3CN 740 (1.6) 752 28 17[19]CHCl3569 594 75 3.7 18[19]CHCl3517 532 39 2.1 19[45]CH2Cl2528 (8.3) 544 90 7.0 1.19 +1.0220[45]CH2Cl2526 (6.0) 544 60 5.0 1.32 +0.9921[45]CH2Cl2532 (4.3) 545 68 4.3 1.35 +0.9922[46]CH2Cl2516 (7.5) 552 80 5.7 1.74 +0.7823[46]CH2Cl2526 (4.6) 562 19 2.0 1.76 +0.7824[31]CH2Cl2517 (7.8) 537 90 9.5 1.58 +0.8725[31]CH2Cl2516 (7.3)371 (9.5)53753794906.2 1.52 +0.8926[47]CH2Cl2516 (6.3)464 (9.7)53553594937.6 1.47 +0.8627[47]CH2Cl2516 (6.5)466 (4.7)372 (5.1)535 9595906.2 1.50 +0.8728[51]CH2Cl2536 (6.7) 544 1