| Due to the unique properties of d-orbital electrons,there are many kinds of bonding ways of transition-metal atoms which lead to abundant types of transition-metal complexes,Cyclometalated compounds,as an important kind of component of organometallic compounds,have attracted great attention and been widely studied in recent decades.Compared with complexes consisting of multiple monodentate ligands and transition-metal atoms,cyclometalated complexes not only have considerable applications in catalysis but show wide and promising applications in fluorescent probes,biological imaging,cancer therapy,molecular electronics and organic light-emiting diodes.In addition to the common cyclometalated complexes which formed by coordination of C^N and N^N ligands,more and more metallaaromatic hydrocarbons have also been reported in recent years.To date,iridaaromatics and osmaaromatics are the mainstream among the reported metallaaromatics.These compounds are all novel in structure,some of them exhibit peculiar optical and electrical properties due to their special aromaticity.In this work,taking cyclometalated complexes and metallaaromatics as research objects,we mainly focused on synthesis as well as further exploration of the optical and electrical properties of mononuclear/multinuclear cyclometalated iridium complexes,irida-and osma-aromatic compounds.In the first part of work,we have synthesized a series of CAN-type diiridium cyclometalated complexes ?-1-?-4 and triiridium cyclometalated complexes ?-5-?-7.Among them,two iridium atoms in complexes ?-1 and ?-3 are thus bound at the central benzene ring in the para-position,whereas those in complexes ?-2 and ?-4 are in the meta-position.The electronic properties were fully characterized combining electrochemistry,spectroelectrochemistry and density functional theory(DFT)calculations.The results show that marked electron transfer occur in conjugated skeletons for all complexes ?-1-?-4 and the different positions on the central benzene ring of iridium atoms can lead to significant differences in electron transfer.The electrochemistry of ?-5 and ?-6 were also explored,cyclic voltammograms of them show separate multiple electron oxidation process.Due to the unstable oxidation states,there were no further measurements with the triiridium complexes.In the second part of this thesis,we have synthesized four near-infrared AIE-active compounds?-2-?-5 and constructed two diosmaaromatic compounds ?-7 and ?-8 by using 4,4'-biphenyldiol and 2,6-dinaphthol as nucleophilic reagents,respectively.The aromaticity of these complexes was confirmed by theoretical calculations on both nuclear independent chemical shfts(NICS)and anisotropy of induced current density(AICD).Cyclic voltammograms suggest both ?-7 and ?-8 are redox-active but only the reduction of them show good reversibility.Compound ?-8 display two splitting and consecutive one-electron reduction process.Then we further investigated the electronic properties of single-electron reduced state of ?-8 by spectroelectrochemistry and DFT calculations.Besides,compound ?-8 is the first dimetallaaromatic compound which contains an octacyclic skeleton.This research makes a groundbreaking guidance in the study of bimetallaaromatic systems.In the third part of work,we have proposed an one-pot synthetic route to obtain a series of pure iridafluoranthenes ?-1-?-9 in high yields by using IrCp*Cl2(PMe3)and 9-ethynyl-9-fluorenol derivatives ?-L1-?-L9 as reagents.The numbers of fused-rings in conjugated skeleton of compounds ?-1-?-9 reach to seven,which is the biggest number of fused rings for metallaaromatic polycyclic hydrocarbons in which the polycyclic skeletons consisting of a metal atom and carbon atoms only.For this kind of compounds,larger conjugated skeleton brings more bathochromic absorption.The results of electrochemical testing and DFT calculations indicate that different substituents or conjugation extent of these compounds play an important role in tuning their electronic properties.Introducing of electron-donating groups can increase the energy levels of HOMO and LUMO,while connecting electron-withdrawing groups brings the opposite.Besides,enlarging the conjugation of ?-skeletons increase the HOMO levels while decrease the LUMO levels,this is also consistent with the red-shifts in UV absorption spectra.This research proposes a new avenue for the design and synthesis of new polycyclic metallaaromatic hydrocarbons and metalla-nanographenes.In the fourth part of work,we have synthesized a series of iridaindenes ?-1-?-10 using substituted phenylacetylenes and IrCp*Cl2(PPh3)in an one-pot route.For compounds ?-9 and ?-10,N,N-diphenylamino groups were introduced to different positions on the iridaindene skeletons.Electrochemical testing indicate all compounds present multi-electron oxidation processes.The first oxidation processes of compounds ?-1-?-8 show appropriate reversibility while both the first oxidation processes and second oxidation prrocesses of compounds ?-9 and ?-10 are reversible.We have measured U?-vis-NIR spectroelectrochemistry of ?-9 and ?-10,and found that the one-electron oxidation state of both ?-9 and ?-10 exhibit absorption bands in NIR region.In addition,we found most of these target compounds show luminescence in solid-state.This research successfully constructs new luminescent compounds and mix-valence system.In the fifth part of the work,we have synthesized a series of stimuli-responsive luminescent cationic iridaindenes ?-1-?-5.Compounds ?-1-?-3 have the same cation,while the peripheral anions are chloride ion,trifluoromethanesulfonate ion and hexafluorophosphate ion,respectively.We replaced the chlorine atom in compound ?-3 with bromine atom and iodine atom to obtain compounds ?-4 and ?-5,respectively.Among compounds ?-1-?-3,after changing the anion,compounds ?-2 and ?-3 show obvious color change of luminescence under external mechanical forces while compound ?-1 does not.While keeping hexafluorophosphate ions as the peripheral anions and changing the halogen ligands,compound ?-4 and ?-5 also display mechanochromism.The luminescence of compound ?-5 is slightly red-shifted compared to compound ?-3.Intramolecular and intermolecular interactions in single crystals were analyzed to found that the mechanochromic behaviors result from change of interactions between peripheral anions and the methoxy groups in the cations.This research shows that changing the peripheral anions of ionic complexes can also be one way to tune their stimuli-responsive luminescent properties. |
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