Dibutylamino Substituted Phthalocyanine.Design,Synthesis,and Properties

Phthalocyanines(Pcs)are conjugated macrocyclic tetrapyrrole compounds of 18 7r-electron aromaticity,which are analogous to naturally occurring porphyrins,possessing an easily tunable molecular structure,easy coordination of central N4 holes,and excellent photosensitivity and catalytic activity.In addition,the rigid coplanar structure features endow Pcs with high electron transport properties,thermal stability and chemical stability.In addition to the traditional applications as dyestuffs,Pcs have attracted great research interests in the recent several decades for their potential in functional molecular material including organic semiconductors for organic photovoltaic cells(OPVs),organic field effect transistors(OFETs)and organic light-emitting diodes(OLEDs),photosensitizers for photodynamic therapy(PDT)and dye-sensitized solar cells(DSSCs),and catalysts for organic synthesis,electrochemical,photochemical catalytic reaction.In addition,the D4 ligand field and the larger conjugated system of phthalocyanine make it suitable for the application of molecular magnets and nonlinear optical materials.In order to meet the application needs of phthalocyanine in various fields,introduction of different functional substituents is an effective way to regulate its molecular structure and electronic structure.In this thesis,N,N-dibutylamino substituted phthalocyanine compounds were used as research objects to synthesize peripheral and non-peripheral tetra-substituted and octa-substituted phthalocyanines.The strong electron-donating effect and large steric hindrance of N,N-dibutylamino groups have greatly modified the spectral properties and crystallinity of phthalocyanine molecules.Furthermore,based on the sandwich-type phthalocyanine-based double-decker compound as a prototype molecule of a single-molecule magnet(SMM),a series of symmetrical,asymmetrical,and supramolecular assembly of molecular magnets were carried out.The following three aspects are the research contents of this paper:(1)N,N-Dibutylamino substituted phthalocyanines:synthesis and propertiesWe first synthesize the corresponding N,N-dibutylamino substituted phthalonitrile as the precursor of phthalocyanine.In refluxing n-pentanol in the presence of magnesium pentanoate led to the corresponding 2,3,9,10,16,17,23,24-octa(N,N-dibutylamino)magnesium phthalocyanine,2,9(10),16(17),23(24)-tetrakis(N,N-dibutylamino)magnesium phthalocyanine,and 1,8(11),15(18),22(25)-tetrakis(N,N-dibutylamino)magnesium phthalocyanine.The magnesium phthalocyanines were dissolved in trifluoroacetic acid to obtain the corresponding metal-free phthalocyanines,then the metal-free phthalocyanines and the transition metal acetate were used as starting materials in refluxing n-pentanol,leading to isolation of the corresponding metal phthalocyanine complexes.It is worth noting that only two simple recrystallizations of the four-regioisomer-containing nonperipherally substituted phthalocyaninato magnesium rendered the successful isolation of the pure 1,8,15,22-tetrakis(dibutylamino)phthalocyaninato magnesium isomer.MALDI-TOF mass spectra,1H NMR spectra,and single crystal X-ray diffraction confirmed the molecular structure of these phthalocyanines.In comparison the absorption spectra of the above three substituted phthalocyanines with unsubstituted phthalocyanine(H2Pc),the introduction of N,N-dibutylamino groups in phthalocyanines lead to the significantly red-shift of the electron absorption,and even the Q-band is no longer split,due to the p-? conjugation between the N,N-dibutylamino and the central phthalocyanine chromophore,which expands the conjugated system of the molecules.Electrochemical behaviors of these phthalocyanines were investigated by cyclic voltammetry(CV),revealing the significant shifts in both the first oxidation and the first reduction potentials to the negative direction,relative to those of H2Pc,confirming the strong electron-donating nature of the dibutylamino groups and the p-? conjugation between the N,N-dibutylamino and the central phthalocyanine chromophore.Density functional theory(DFT)calculation directly reveals the nature and the relationship of the p-? conjugation from the peripheral or non-peripheral N,N-dibutylamino and phthalocyanine central rings.(2)Symmetric and asymmetric sandwich-type N,N-dibutylamino substituted phthalocyanine based double-decker complexes SMMs:synthesis and propertiesBy using 2,3,9,10,16,17,23,24-octa(N,N-dibutylamino)metal-free phthalocyanine H2?Pc[N(C4H9)2188 as starting material,the neutral double-decker compound Tb {Pc[N(C4H9)2]8} 2 were obtained irn refluxing n-octanol and trichlorobenzene(TCB).Treatment of Tb(acac)3·nH2O with H2?Pc[N(C4H9)2]8} in refluxing n-octanol afforded the half-sandwich complex Tb{Pc[N(C4H9)2]8?(acac),which further reacted in situ with Li2Pc,giving the unsymmetrical double-decker complex in neutral form(Pc)Tb?Pc[N(C4H9)2]8?.Then chiral binaphthyl and dibutylamino substituents were incorporated onto the periphery of each phthalocyanine ligand in the bis(phthalocyaninato)terbium double-decker compound,resulting in the chiral heteroleptic bis(phthalocyaninato)terbium complex(J/R)/(S)-[Pc(OBNP)4]Tb{Pc[N(C4H9)2]8}.Magnetic investigation at low temperatures indicated that all these complexes are single-ion magnets(SIMs).The effective energy barriers(Ueff)of the three SIMs are 752,939 and 638 K,and the hysteresis loops could be observed at 25 K(200 Oe/s),30 K(200 Oe/s)and 25 K(500 Oe/s),respectively.Density functional theory(DFT)calculation for the electrostatic potential of the TbD+ in these complexes were compared to the unsubstituted phthalocyanines double-decker SIM,revealing the enhanced coordination field strength around the Tb1U after peripherally incorporating the N,N-dibutylamino groups,resulting in the enhancement of their magnetic performances.Furthermore,in(Pc)Tb?Pc[N(C4H9)2]8?,the electrostatic potential around the Tb3D is further enhanced relative to its symmetric counterpart.Moreover,organic radicals play an important role in improving the magnetic performance of bis(phthalocyaninato)terbium double-deckers in comparison with that of the corresponding reduced form SIMs.At the end of this chapter,it is noteworthy that the effective energy barrier of(Pc)Tb?PC[N(C4H9)218?,939 K,and the blocking temperature,30 K(200 Oe/s),are the highest ones among all the sandwich-type tetrapyrrole lanthanide SIMs.(3)Fabricating bis(phthalocyaninato)terbium SIM into tetrakis(phthalocyaninato)terbium SMM:synthesis and propertiesReaction of 1,4,8,11,15,18,22,25-octabutoxy metal-free phthalocyanine with half-sandwich complex Tb(Pc)(acac)afforded the unsymmetrical heteroleptic bis(phthalocyaninato)terbium double-decker compound in the protonated form.According to the single crystal structure,its twist angle(which is defined as the rotation angle of one coordination square away from the eclipsed conformation of the two macrocycles)is 28.33°,which reveals a severe deviation of the coordination polyhedron from the square-antiprismatic geometry for the Tb3+ in this double-decker,leading to the tUeff of this SIM only 180 K with the hysteresis loops observed only at 2 K(500 Oe/s).After being fabricated into the pseudo-quadruple-decker with the help of Na+ connection,the average twist angle in each double-decker unit gets increased to 34.11°,enhancing the magnetic anisotropy in the double-decker units.This,further improving the magnetic properties of the pseudo-quadruple-decker molecules,resulted in the Ueff increasing to 528 K,and the hysteresis loop observing at 25 K(500 Oe/s).The present result is surely helpful towards developing novel tetrapyrrole lanthanide SMMs through rational design and self-assembly from bis(tetrapyrrole)lanthanide single ion magnet(SIM)building block.