Student Project Abstracts 2005 - Pluto - University of Washington

Synthesis of Nonlinear Optical-Active MaterialsDan Daranciang, Washington University in St. LouisDonald Responte and Werner KaminskySynthesisDepartmentofofNonlinearChemistry, UniversityOptical-Activeof WashingtonMaterialsroductionSince the first observation Dan Daranciang of second harmonicWashington University in St. Louiseration (SHG) in 1961 by Franken, multiplelinear optical materialse been characterized anddied. Franken irradiated INTRODUCTIONrtz with 694 nm light, andhis surprise, he detecteditted photons at 347 nm,f the original wavelengthThe key characteristic of all NLO active materialsis seen Donald in their Responte packed and lattice Werner geometry. Kaminsky In order toDepartment of Chemistryexhibit second-, University third-, or of nth-order Washingtonoptical effects, theunit cell of the material must be noncentrosymmetric.Otherwise, upon excitation of thematerial, dipole-dipole METHODS vibrations occur in equalmagnitude but opposite direction, and therefore canceleach other out. Another consideration in our designwas how to ensure that our products, in addition tobeing NLO active, could potentially have photonicsapplications. We decided to use aromatic functionalgroups in our products. Aromatic rings containregions of high -electron density, which would giveSince the first observation of second harmonic generation The key characteristic of all NLO active materials is seen(SHG) in 1961 by Franken, multiple nonlinear optical materials in their packed lattice geometry. In order to exhibit second-,have been characterized and studied. Franken irradiated quartz third-, or nth-order optical effects, the unit cell of the materialwith 694 nm light, and to his surprise, he detected emitted photonsmust be non-centrosymmetric. Otherwise, upon excitation of theat 347 nm, half the original wavelength and therefore twice material, dipole-dipole vibrations occur in equal magnitude buttherefore twice thethe energy of the incoming photons.FigureThis1.singularSchematicobservation,ofthe opposite direction, and therefore cancel each other out. Anotherresult of a second order phenomenon SHG. Two involving photons the absorption of of consideration in our design was how to ensure that our products,two photons, spawned a new wavelength classification of materials: (red) are nonlinearin addition to being NLO active, could potentially have photon-optical (NLO) materials. NLO absorbed materials to promise reach a to have great our ics applications. compounds We the decided ability to use to aromatic readily functional transfer groups charge. inutility in developing Synthesis tomorrow’s of Nonlinear "virtual" technology. excited Optical-Active Taken state. together, A the Materials our products. Aromatic rings contain regions of high π-electronDan Daranciang, Washington University in St. Louissheer quantity and variety of Donald NLO single effects Responte photon that and have Werner at been Kaminsky /2 observed density, which would give our compounds the ability to readilyallow us to harness the properties Department of Chemistry, light in exciting University and of unexpectedways. Photonics-based technology sees use today in everything With this in mind, we chose to study the reaction of aryl iso-Washington(blue) emittedtransfer charge.IntroductionThe key characteristic of all NLO active materialsSince from the pulse first measurement observation of devices second to harmonic fiber optics. is seen in their packed lattice thiocyanates geometry. with In order (S)-2-butanol. to (S)-2-butanol is a relatively lowgeneration (SHG) in 1961 by Franken, multiple exhibit second-, third-, or nth-order molecular optical weight effects, chiral theNLO materials promise to have greatligand with only one possible nucleophilicnonlinear optical materialsunit cell of the material must be noncentrosymmetric.Otherwise, reaction, upon excitation and therefore of the its product with a substituted aryl isothio-have been characterized andstudied. Franken irradiatedmaterial, dipole-dipole vibrations cyanate is occur easily in predictable. equal Since it is chiral, the product wouldquartz with 694 nm light, andmagnitude but opposite direction, and therefore cancelhave a chiral carbon center, and we were therefore assured that theto his surprise, he detectedeach other out. Another consideration in our designemitted photons at 347 nm,was how to ensure that our unit products, cell of the in addition product to could not have a center of symmetry.half the original wavelengthbeing NLO active, could could potentially not have photonics a center of symmetry.and therefore twice theapplications. We decided to use aromatic functionalSenergy Figure of 1. the Schematic incoming of SHG.Figure 1. Schematic ofSHG. Two Two photons photons of wavelength of λ groups (red) are in absorbed our products. Aromatic rings contain Nphotons. to reach This a "virtual" singular excited wavelength state. A single (red) photon are at λ/2 (blue) regions is emitted. of high -electron density, which would give COHobservation, the result of a absorbed to reach a our compounds the ability to readily transfer charge. +involving the absorption of single photon at /2Sof aryl isothiocyanates with R (S)-2-butanol. (S)-2-(blue) is emittedtwo photons, amples spawned are KTiO a new 4and KDP, potassium dihydrogen butanol phosphate), is a relatively low molecular weight chiralsecond order phenomenonWhile many such"virtual" excited state. Amaterials have beenWith this in mind, we chose to study the reactiondiscovered (two ex-classification of materials: nonlinear optical (NLO) ligand with only one possiblea great deal of work remains. For one, though the “classic” examplesin developing of NLO tomorrow’s materials technology. have certainly Taken been proven isothiocyanate SHG active, is easily predictable. Since it is chiral,substituted nucleophilic phenyl reaction, isothiocyanate (S)-2-butanolmaterials. NLO materials promise to have great and therefore its product with a substituted arylutilitytogether, experimentation the sheer quantity we and have variety performed of NLO effects shows that other product compounds would have a chiral carbon center, and wethat have been observed allow us to harness the were therefore assured that the unit cell of the productproperties can have of light even in larger exciting SHG and efficiencies. unexpected ways. In addition, the current exampleof chromophores technology sees has use recently today attracted in much experimental N SHcould not have a center of symmetry.N SPhotonics-basedCOHeverything from pulse measurement devices to fiber+interest, but these compounds are difficult to synthesize, involveoptics.SROWhile lengthy many reaction such materials sequences, have been and discovered afford increasingly smaller percentexamples yields are at each KTiOstep.4 and KDP, potassiumSRsubstituted phenyl isothiocyanate (S)-2-butanol(twodihydrogen phosphate), a great deal of work remains.For one, We though proposed the “classic” this summer examples to of synthesize NLO and characterizeHN Smaterials by X-ray have certainly diffraction been and proven SHG SHG emission active, experiments a certainphenyl-substituted i-butyl-N-phenyl thiocarbamateexperimentation we have performed shows that otherclass of materials, i-butyl-N-phenyl thiocarbamates. Through thisOcompounds can have even larger SHG efficiencies. InRSaddition, work, the we current hypothesized example of that chromophores we could lay has out a basis for the simple,Figure 2. The reaction of aryl isothiocyanates with (S)-2-butanol. When Rattracted rational much synthesis experimental and design interest, of NLO but active materials, which = EWG, the isothiocyanate undergoes electrophilic attack at the cumulenerecentlyphenyl-substituted i-butyl-N-phenyl thiocarbamatethese compounds are difficult to synthesize, involvecarbon, affording the phenyl-substituted i-butyl-N-phenyl thiocarbamate.lengthy demonstrated reaction sequences, significant and afford activity increasingly compared to the compoundsThe geometry at the indicated carbon on the butanol is preserved.Figure 2. The reaction of aryl isothiocyanates with (S)-2-smaller currently percent yields in wide at each use. step.butanol. When R = EWG, the isothiocyanate undergoesWe proposed this summer to synthesize and electrophilic attack at the cumulene carbon, affording thecharacterize by X-ray diffraction and SHG emission phenyl-substituted i-butyl-N-phenyl CMDITR thiocarbamate. Review of Undergraduate The Research Vol. 2 No. 1 Summer 2005 25experiments a certain class of materials, i-butyl-Nphenylthiocarbamates. Through this work, we preserved. preserved.geometry at the indicated carbon on the butanol ishypothesized that we could lay out a basis for the Aryl isothiocyanates were selected because of theirrgy of the incomingtons. This singularervation, the result of aond order phenomenonolving the absorption ofphotons, spawned a newssification of materials: nonlinear optical (NLO)terials.lity in developing tomorrow’s technology. Takenether, the sheer quantity and variety of NLO effectst have been observed allow us to harness theperties of light in exciting and unexpected ways.otonics-based technology sees use today inrything from pulse measurement devices to fiberics.hile many such materials have been discoveredo examples are KTiO 4 and KDP, potassiumydrogen phosphate), a great deal of work remains.r one, though the “classic” examples of NLOterials have certainly been proven SHG active,erimentation we have performed shows that otherpounds can have even larger SHG efficiencies. Inition, the current example of chromophores hasently attracted much experimental interest, butse compounds are difficult to synthesize, involvegthy reaction sequences, and afford increasinglyaller percent yields at each step.e proposed this summer to synthesize andracterize by X-ray diffraction and SHG emissioneriments a certain class of materials, i-butyl-Nnylthiocarbamates. Through this work, weWith this in mind, we chose to study the reactionof aryl isothiocyanates with (S)-2-butanol. (S)-2-butanol is a relatively low molecular weight chiralligand with only one possible nucleophilic reaction,and therefore its product with a substituted arylisothiocyanate is easily predictable. Since it is chiral,the product would have a chiral carbon center, and wewere therefore assured that the unit cell of the productFigure 2. The reaction of aryl isothiocyanates with (S)-2-butanol. When R = EWG, the isothiocyanate undergoeselectrophilic attack at the cumulene carbon, affording thephenyl-substituted i-butyl-N-phenyl thiocarbamate. Thegeometry at the indicated carbon on the butanol is