Patent Application: US-32812603-A

Abstract:
complexes of organic ligands with a metal ion exhibit unique conformation and spectroscopic properties upon changes in oxidation state of the metal ion . the metal is a redox - active metal ion and may possess additional ligands bonded to it . the organic ligand has three “ arms ” that are linked together at a central atom ; each arm contains atoms that may also coordinate to the metal ion . at least two of the arms possess chromophoric properties . at least one arm contains two different groups that may coordinate to the metal ion . in one oxidation state , a first atom binds to the metal . in a second oxidation state , a second atom binds to the metal . this change in coordination of the metal ion results in a rotation of one of the arms , which changes the orientation of another group , which inverses the orientation of the two chromophoric species with respect to one another .

Description:
in the formula shown in fig1 , a is an atom that can coordinate to a metal ion such as nitrogen , oxygen , or sulfur ; c 1 and c 2 are the same or different chromophores capable of absorbing light that also contain an atom that may coordinate to a metal ion ; r 1 – r 4 are linker groups , and may be —( ch 2 ) n —, — o —, — s —, — nr 8 —, carbonyl , carboxyl , wherein n can be an integer of from 1 to 4 r 8 is straight - chain or branched alkyl having from 1 to 8 carbon atoms . r 5 – r 7 are terminal groups which can be hydrogen , c 1 – c 8 branched or straight chain alkyl groups , c 6 – c 14 substituted or unsubstituted aromatic groups and heteroaromatic groups having from one to three hetero atoms . the hetero atoms can be nitrogen , sulfur , or oxygen . m is a metal ion which can exist in at least two oxidation states . the basic switching mechanisms of the present invention can be used with any metal ion that exists in two oxidation states . when using circular dichroism spectroscopy as a spectroscopic reporter , the preferred metal ions are those with trigonal bipyramidal coordination sphere , such as copper and zinc . the chromophores , which may be the same or different , can be any chromophore that also binds to a metal . examples of such chromophores are substituted and unsubstituted pyridines , quinolines , imidazoles , pyrazoles , pyrazines , pyridiazines , benzimidazoles , phenanthrolines , and related heterocyclic compounds having one or more rings , which may be fused , that are chromophores that also bind to a metal ion . the substituents can be aliphatic , aromatic , or alkyl aromatic having from 1 to 16 carbon atoms , nitro , cyano , c 1 – c 8 alkoxy , c 1 – c 16 aryloxy , c 1 – c 8 alkylamino , c 1 – c 16 arylamino , azo , halo , sulfonyl , phosphoryl , c 1 – c 8 alkylthio , c 1 – c 16 arylthio , or any other substituent that does not affect the metal ion binding and the chromophoric properties of the molecule . the present invention is thus directed to coordination compounds which can be used to exhibit conformational and spectroscopic properties depending upon the oxidation state of the metal ion complexed within . the coordination compounds of the present invention include any chromophore that can bind to a metal , a coordination metal which can exist in two valence states , and a chiral unit that can rotate so as to obtain distinguishing physical properties of the coordination compounds . by inverting the orientation of the two chromophores in three dimensions in the coordination compounds of the present invention , one can produce a change in the differential absorption of circularly polarized light or rotation of plane polarized light . this changes both the shape of the molecules and the optical properties of the molecules . these compounds can be used for redox write , chiroptical read storage devices , as well as in place of liquid crystal materials in display devices . the chirality may be inverted for the oxidation states , such that the oxidized compound gives “+” chirality and the reduced compound gives “−” chirality . an illustration of such a compound is shown in fig1 , in which cu ( i ) is complexed with a sulfur atom and cu ( ii ) is complexed by an oxygen atom . the δ ε for each of cu ( i ) and cu ( ii ) are shown in the graph in the center of fig1 . the present invention is similar to the “ on / off ” molecular switches as described by ( zahn et al ., 1998 and zahn et al ., 1998 ) in that molecular motion in a coordination complex results in a change in signal in the circular dichroism spectrum . however , the nature of the motion is different , and the new switch does not simply turn the signal on and off but causes an interconversion between mirror images ( i . e ., “+/− switch ”). the following examples illustrate compounds which can be used for electron - driven chirality switches . these examples are solely for illustration , and in no way are intended to limit the invention . to 24 g ( 0 . 016 mol ) of commercially available l - methionine in 9 ml of water was added 2 . 7 g koh ( 0 . 048 mol ) and 4 ml of ethanol . the solution was heated to reflux and 7 . 1 g 2 - bromomethyl - quinoline ( 0 . 032 mol ) dissolved in 20 ml of ethanol was added over 10 minutes . the resulting solution was refluxed for 60 minutes , cooled and evaporated to one half the original volume . the solution was extracted with methylene chloride . the methylene chloride layer was collected , dried over anhydrous potassium carbonate and evaporated to dryness . column chromatography ( np - silica , ethyl acetate / hexanes : 3 / 1 ) yielded 2 g ( 29 %) of the elementally pure product . deoxygenated , hcl - free methylene chloride ( 10 ml ) was added to mixture of 100 mg of the solid ligand ( 0 . 23 mmol ) and 85 mg of cu ( mecn ) 4 pf 6 ( 0 . 22 mmol ) under nitrogen . the solution was stirred for 5 minutes and 20 ml diethylether were added to crystallize the copper complex . the precipitate was collected , washed with diethylether and dried in vacuo to yield 122 mg ( 82 %) of the desired compound elementally pure . a mixture consisting of 180 mg of the solid ligand ( 0 . 417 mmol ) and 162 mg of cu ( clo 4 ) 2 × 6 h 2 o ( 0 . 418 mmol ) was dissolved in 30 ml methanol . upon stirring for one hour a precipitate formed , which was collected washed with methanol and dried in vacuo to yield 140 mg of the elementally pure copper complex . to 13 ml of dimethylformamide at 80 ° c . were added 500 mg of the bromide and 0 . 45 ml of degassed i - pr 2 etn . to this solution were added 100 mg of l - methionine dissolved in 3 ml of a 2 : 1 water : dmf mixture containing 10 mg sodium bicarbonate dropwise . the reaction was stirred for 5 hours at 80 ° c ., cooled and evaporated to dryness . the remaining solid was taken up in a methylene chloride / sodium hydroxide ( 1 m ) mixture ( 1 : 1 ). the organic layer was collected , dried over anhydrous potassium carbonate and chromatographed to yield 200 mg of the desired ligand . the ligand n , n - bis [( 2 - quinolyl ) methyl ]-( s )- methly - l - cysteine was prepared from the dropwise addition of ( s )- methyl - l - cysteine methylester hydrochloride ( 2 . 0 g , 10 . 8 mmol ) in 10 ml dmf to a stirring solution of 2 - bromomethylquinoline ( 4 . 8 g , 21 . 6 mmol ) and sodium bicarbonate ( 4 . 1 g , 49 mmol ) in 40 ml . the mixture was allowed to react for 4 h at 80 ° c . evaporation of the solvent followed by column chromatography with 3 : 1 hexancs : ethyl acetate ( rf 0 . 3 ) afforded the ester of the ligand ( 1 . 7 g , 82 %). saponification was achieved by stirring the ester ( 1 . 9 g , 4 . 4 mmol ) in 8 ml thf with lioh ( 4 . 6 ml , 1m ) for 2 . 5 h . the solution was then extracted with methylene chloride , and the aqueous layer acidified with 0 . 5m hclo 4 to ph 6 . several extractions with methylene chloride followed by drying and evaporation of the solvent afforded the crude acid . purification by column chromatography with ethyl acetate afforded the pure ligand ( 0 . 57 g , 31 %). complexation of the pure ligand ( 0 . 097 g , 232 mmol ) with equimolar amount of cuclo 4 . h 2 o in meoh afforded blue crystals which were collected by vacuum filtration and washed with ether ( 0 . 129 g , 78 %). 3 . 27 grams of 2 - bromomethylquinoline and 2 . 8 g of sodium bicarbonate were stirred in 15 ml of dmf . the mixture was heated to a constant temperature between 60 – 70 degrees with magnetic stirring . 1 . 0 g of l - methioninol dissolved in 5 ml of dmf was added drop wise to the reagent flask . the resulting mixture was heated between 60 – 70 degrees celsius . after cooling down to room temperature , sodium bicarbonate was filtered and the dmf was evaporated and vacuum dried overnight purification with silica column chromatography ( rf 0 . 15 ) yielded 1 . 17 g ( 38 . 11 %) of ( l )- n , n - bis ( 2 - quinaldyl ) methionol . 100 mg of n , n - bis ( 2 - quinaldyl ) methioninol was dissolved in 1 ml of methanol . 0 . 99 g of cu ( ii ) clo 4 . 6h 2 o in 1 – 2 ml of methanol was slowly added to the above solution . a green - blue precipitate formed immediately . the precipitate was filtered and washed with ethyl ether . vacuum drying overnight yielded the complex ( 41 . 58 %). the foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can , by applying current knowledge , readily modify and / or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept , and , therefore , such adaptations and modifications should and are intended to be comprehend within the meaning and range of equivalents of the disclosed embodiments . it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation . the means , materials , and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention . thus , the expressions “ means to . . . ” and “ means for . . . ”, or any method step language , as may be found in the specification above and / or in the claims below , followed by a functional statement , are intended to define and cover whatever structural , physical , chemical , or electrical element or structure , or whatever method step , which may now or in the future exist which carries out the recited functions , whether or not precisely equivalent to the embodiment to embodiments disclosed in the specification above , i . e ., other means or steps for carrying out the same function can be used ; and it is intended that such expressions be given their broadest interpretation . burk et al ., angew . chem . int . ed . engl . , 29 : 1462 ( 1990 ). canary et al ., “ conformationally driven , propeller - 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