Synthesis And Function Studies On New Porphyrin Dimers As Well As Chiral Recognition Studies On Mesoporous With Chiral Porphyrin Encapsulated

The preparation of well defined arrays of porphyrins is a popular area ofresearch,for oligomeric porphyrins play a number of critical biological rolessuch as energy and electron transfers,molecular binding,multielectron redoxcatalysis,light harvesting,and in organic magnetic materials. Porphyrin is a bigconjugate macrocycle compound,its periphery has 12 active positions,whichcould connect with different function groups to enhance the conjugation ofplanar constitution,multiformity of conformation and properties f assembly.The high speed development in electron technology has result therequirement to the more complex and smaller electron parts of an apparatus.Soit became the important task in electronic region that how to develop newtechnology producting electronic parts of an apparatus on the molecule level.Porphyrin monomer can make electron transfer faster and easier owing to thestructure of alternate single-double bonds onjugate macrocycle,therefore,it ispossible that metals in the square are substituted with porphyrins to serve as theextensiven-conjugated structure.Synthesis and characterization of oligoporphyrin arrays have beeninvestgated strongly recently. In reactive arrays,particular physical and opticalproperties are produced through electronic interaction in porphyrin ormetalloporphyrin. The important development of porphyrin construct leads to alot of new compounds which possess potential application values in electronand energy transfer.With the development of the synthesis method of oligoporphyrin, thenew method of the directly coupling of porphyrin monomers was discovered.Under the mind direction, a mesoporphyrin dimmer was assembled by linkingwith periphery substitutes of porphyrin in a one-step,one-pot synthesis at a lowtemperature. The problems of tedious preparation,multiple products andinconvenient separation were resolved by the method.The compounds werecharacterized by elemental analysis,MS,1HNMR,UV-vis,IR,respectively,which proved that these compounds are the target products.Then , thefluorescence properties,surface photovoltage properties,electrochemistry,EPR and heat stability of porphyrin monomer,dimer and transition metalporphyrin were investigated by comparing them.Chiral recognition is an attractive subject in the area of host-guestchemistry,since it is a fundamental process for a range of chemical andbiological phenomena. Several types of host molecules for chiral recognitionstudies have been reported because of their biological and chemical importance.Among them, porphyrins are relatively accessible molecules, and have beenused in the recognition studies for the past two decades. However,porphyrinsfor chiral recognition were restricted due to their poor stability in solution. Auseful means to improve the stability of porphyrin is by encapsulating it intomicroporous materials such as zeolites,mesoporous. There are no reports onencapsulation of chiral porphyrin and their chiral recognitions.It is, therefore,important to study this system and to focus on chiral recognition of the host forsmall chiral molecules and their photophysical properties. It has been proposedthat the enantioselectivity of the host for amino acid could be effectivelyenhanced by constructing a specific chiral environment derived from protectedamino acid on host porphyrin. In this research, we designed and synthesized aporphyrin that contains an amino acid on the porphyrin plane (Figure) andencapsulated the porphyrin molecule with chiral recognition into the channelsof SBA-15 to make it have chiral recognition functions. The resultant materialwas characterized by DR-UV-vis,XRD,TEM,N2 absorbtion and CD.Acombination of techniques such asUV-vis and CD spectroscopy was employedto study the chiral recognition of it.1. Synthesis and Character of porphyrin ligandsAccording Adler-longo method, we have synthesized the porphyrinmaterials for the investigation. Structures of the ligands are follows:(1) 5,10,15,20 – tetraphenyl porphyrin,R1 = R2 = R3 = R4 = R5 = H(2) (5 -para-hydroxyphenyl – 10,15,20 -tri – phenyl) porphyrin,R1 = OH,R2 = R3 = R4 = R5 = H(3) (5 -para-carboxyphenyl – 10,15,20 -tri – phenyl) porphyrin,R1 = CO2H,R2=R3= R4 = R5 = H(4) (5 -ortho-hydroxyphenyl – 10,15,20 – tri – para -nitryl phenyl) porphyrin,R1 = H,R2 = R3 = R4 = NO2,R5 = OHThe identities of the products were confirmed by element analysis,MS,1HNMR, UV-vis, IR, DTA and TGA, Molar conductiance, respectively.2. Synthesis and Character of porphyrin dimer and transition metal dimerThe reaction process can be represented by equation:The identities of the products were confirmed by element analysis,MS,1HNMR,UV-vis,IR,respectively.3. Chiral recognition of mesoporous with chiral porphyrin encapsulatedA combination of techniques such as XRD,TEM,UV-vis,nitrogenadsorption , CD spectroscopy was employed to confirm that we havesuccessfully incorporated chiral porphyrin into the interior surface of thechannels of mesoporous molecular sieve. The chiral mesoporous showsdifferent chiral recognition abilities for small amino acid such as L and D type.The experiments demonstrate that the D type amino acid is more tightly boundto the host than its optical antipode.4. The investigation of porphyrins properties(1)The fluorescence propertyIn the paper, the fluorescence properties of all prophyrin ligands,porphyrin dimer and metallodiporphyrins were investigated, and the quantumyields of these compounds at room temperature were obtained. Thefluorescence intensity and the quantum yield of porphyrin dimer is the highestin all compounds in the paper. The electronic donating hydroxyl groupenhances the fluorescence intensity of porphyrin , and theelectron-withdrawing group decreases the fluorescence intensity of porphyrin.(2)The surface photovoltage propertyThrough SPS and FISPS, the photophysic property of porphyrins werestudied. The results show that porphyrin is p-type semiconductor. The band ofSPS represents the transition of π→πж. The SPS is similar with UV-visspectrum, and the stronger the fluorescence intensity were, the weaker thesurface photovoltage were.(3) Electrochemistry propertyThe redox properties of all porphyrins were researched by the cyclicvoltammetry, the redox potentials were obtained. The redox processes ofmetalloporphyrins are more than that of porphyrin ligands owing to the redoxof the metal ion.(4) EPR propertyEPR of the porphyrin dimer and zinc porphyrin dimer as compared to relatedmonomers were studied. It shows clearly that a π-π interaction exists betweenthe two macrocycles of the dimer.