Design,Synthesis,and Semiconducting Properties Of Functiona Tetrapyrrol Compounds

Due to the especially electrical,magnetic,and optical properties,porphyrins and phthalocyanines which own 18 ?-electron aromatic systems have showed unique characteristic features and advantages in different areas such as cell imaging,organic filed-effect transistors,sensors,single-molecular magnet,electrochemistry and liquid crystals.Especially,the sandwich-type phthalocynaine complexes,two or three Pc rings are closely bonded in a "face-to-face" manner by rare earth atoms through coordination bonds,resulting in more extended?-conjugated electronic structure/material(MPc2 and M2Pc3)and thus higher conductivity and carrier mobility.Except coordinating with metal along axis direction,amplified conjugated system along phthalocyanine planar direction can also be extended.Due to planar molecular structure and extended conjugation system,the semiconducting property can also be improved.Furthermore,depending on the application,it is easy to functionalize the MPc2 and M2Pc3 by tuning the central rare earth atom(s)or the peripheral and/or the bay positions of the ?-conjugated Pc skeletons with different functional substituents,improving the solubility and tuning the simplifying fabrication of devices.High-performance organic field-effect transistors and sensors through molecular design,device fabrication,and post-processing are called hot topics in the field of materials.This article conducts research from the corresponding aspects:(1)An amphiphilic mixed(phthalocyaninato)(porphyrinato)europium(?)triple-decker complex[Pc(OPh)8]Eu[Pc(OPh)8]Eu[TP(C=CCOOH)PP](1)with potential ambipolar semiconducting HOMO and LUMO energy levels has been designed,synthesized,and characterized.The OFET devices fabricated by quasi-Langmuir-Shafer(QLS)technique at the air/water interface with nanoparticle morphology display hole mobility of 7.0×10-7 cm2 V-1 s-1 and electron mobility of 7.5×10-7 cm2 V-1 s-1,which reflects its ambipolar semiconducting nature.However,the performance of the devices fabricated via a"phase-transfer" method from n-hexane with one-dimensional nanoribbon morphology was significantly improved by 3-6 orders of magnitude in terms of hole and electron mobilities,0.11 and 4×10-4 cm2 V-1 s-1 due to the enhanced ?-?interaction in the direction perpendicular to the tetrapyrrole rings associated with the formation of a dimeric supramolecular structure building block depending on the intermolecular hydrogen bonding between the neighboring triple-decker molecules in the one-dimensional nanoribbons.(2)Thin film transistor fabricated from a binuclear phthalocyanine dimer-containing yttrium double-decker complex[{Pc(OC4H9)8}Y{BiPc(OC4H9)12}Y{Pc(OC4H9)8}]using QLS technique exhibits good ambipolar OFET device performance with carrier mobility of 2.3 and 0.8 cm2 V-1 s-1 for electrons and holes,respectively,representing the highest mobilities achieved so far for solution-processed small-molecule single-component-based ambipolar OFET devices.The ambipolar semiconducting nature of this compound was further confirmed in an unambiguous manner by the high sensitive response of the device towards both oxidizing gas NO2 and reducing gas NH3 in the concentration range of 0.5?3 ppm and 7.5?20 ppm at room temperature.Such a low LOD(limit of detection)and good response make the device possible for practical application.The present result is truly helpful for the synthesis and design of phthalocyanine-based organic semiconducting materials with multilinear extended conjugated electronic system.(3)A novel dimeric phthalocyanine involved sandwich-type triple-decker complex which combines two triple-decker phthalocyanines by a fusing benzene ring,[Pc(SC6H13)8]2Eu2[BiPc(SC6H13)12]Eu2[Pc(SC6H13)8]2(1),has been synthesized.Combination of the dimeric phthalocyanine framework with the sandwich triple-decker structure not only extends the ?-conjugated system along the two orthogonal directions of the both parallel and perpendicular to the Pc macrocycles,but more importantly ensures its HOMO and LUMO levels into the range of air-stable ambipolar organic semiconductor.Furthermore,the defect-free single-crystal microsheets of the compound 1 are successfully obtained by a simple solution-based method with a large size of 100?350 ?m in length and 20?120 ?m in width,respectively.Significantly,the single-crystal microsheet-based organic field effect transistors(OFETs)of 1 are developed to exhibit excellent carrier mobilities of 18 cm2 V-1 s-1 for holes and 0.3 cm2 V-1 s-1 for electrons under ambient condition,representing the best result achieved so far for phthalocyanine-based OFET devices.(4)Incorporation of the dimeric phthalocyanine into sandwich phthalocyaninato europium framework extends the conjugated electronic molecular structure and optimizes the ambipolar semiconducting properties of the QLS thin film-based OFET device,resulting in a significant increase in the hole and electron mobilities from 4.30×10-7 and 0.70×10-7 cm2 V-1 s-1 for monomeric phthalocyanine-containing triple-decker Eu2[Pc(SC6H13)8]3(1)to 0.07 and 0.06 cm2 V-1 s-1 for the dimeric phthalocyanine-containing quintuple-decker[Pc(SC6H13)8]2Eu2[BiPc(SC6H13)12]Eu2[Pc(SC6H13)8]2(2).This in turn induces an enhanced gas sensing detection performance for NO2 with the response increasing from 11.7%(500 ppb)for 1 to 23.4%(500 ppb)for 2.The present result appears interesting in terms of improving the gas-sensing properties of phthalocyanine-based molecular materials via molecular design and synthesis rather than tuning the film morphology.