Functional Molecular Gels Based On Quinacridone Derivatives

The research on novel functional materials has attracted increasing interest in recent years for its potential applications and effects in recording, solar cell, sensors, biological separation, and organic field effect transistor fields accompanied with the development of scientific technology. Organic molecular gel system is an important part of supramolecular assembled soft matter, which could be used in imaging, commodity, template, food and oil industry fields. Recently, design and synthesis of novel organic materials, preparation of functional molecular gel, and their applications into photoelectric devices and drug release have been intensively studied.Organic small molecules possess several notable advantages including easy design and synthesis, mechanical flexibility, and high performance. Intermolecular interactions such asл…л, hydrogen bonding, van der Wall and metal-metal interactions, owning outstanding multiple characteristics, direction, selectivity, cooperation and reversibility, are the headspring and power of molecular assembly. Thus, design of molecular materials with specific purpose, tuning molecular interactions, changing molecular configuration or packing model in aggregated states, and final fabrication of molecular gel with particular morphology and functionality are the main points of obtaining functional materials. Deep understanding the principle and essence of intermolecular interactions based on outstanding responsive behaviors of molecular gel plays an important role in research on gelation and design of functional materials. This thesis work concentrated on design and synthesis of quinacridone derivatives and studies on functional molecular gel. 1. In chapter II, we have designed and synthesized mono-and di-cholesterol appended quinacridone derivetives MCCn (n= 4,6,8) and DCCn (n= 4,6,8,10) with different length of alkyl linker, and urea-functionalized quinacridone molecules DUCn (n= 6,8). The molecular structures have been confirmed by 1H NMR, mass spectra, and element analyses, and DCCn and DUCn are all centrosymmetric in solution. Simple synthesis approaches and high yields provide excellent conditions for investigation of their supramolecular assembly properties and production of micro materials in a large amount.2. In chapter III, we have investigated the ultrasound-induced gelation properties of di-cholesterol appended quinacridone derivatives DCCn (n= 4,6,8,10), fabricated different morphological nano/micro-materials, and observed mechanochromic fluorescence of the xerogel.Compounds DCCn showed different outstanding assembly properties that DCC4 formed some bulky precipitates, DCC10 kept the clear sol state, but DCC6 and DCC8 gave stable organogel immediately after sonication treatment. These two compounds have the lowest CGCs in ultrasound-responsive gelators, and can be defined as "supergelators". FESEM and TEM microscopes were used to study the morphologies of the xerogel from EtOAc: DCC4 precipitates were organized with uniform peony-like 3D microstructures, suggesting that the well-defined microstructures were constructed through the hierarchial association of slice minicrystals. In contrast, both of gelators DCC6 and DCC8 formed well-defined 1D nanofibers, and the most striking difference between the nanostructures of these two samples was that DCC8 formed left-handed chiral helical fibers while DCC8 did not form such helical patterns at all. The morphological properties indicated that slight change of molecular structure could lead to the obvious variation of molecular assembly characteristics. The ultrasound-induced organogel process was characterized by kinetic UV-vis and photoluminescence spectroscopic methods suggesting the formation ofл-лaggregates in the gel state. Experimental results demonstrated that the ultrasound could promote molecules to contact frequently in the solution and induce semistable initial aggregates, which propagate to form nano/micro superstructures. The aggregation model was optimized by semiempirical AM1 calculation suggesting the hierarchical self-assembly process. In addition, the formed xerogel film exhibited mechanochromic properties, and the phase transition process was accompanied by the fluorescence changes between yellowish green and orange. We could understand the mechanism of stimuli-responsive functional gelation based on molecular design, tunable configuration and packing, changing environments and preparation of gel, which will help design more excellent and outstanding responsive materials.3. In chapter IV, we have investigated multi-stimuli-responsive behaviors of the mono-cholesterol substituted quinacridone derivatives MCCn (n= 4,6,8).MCC6 could form gels in a wide variety of organic solvents immediately after sonication. It could also form opaque gel by directly cooling the hot solution to room temperature at relative higher concentration. MCC8 formed a stable gel exclusively upon ultrasound irradiation, and the sol state can not convert into gel state without sonication. At room temperature compound MCC4 in cyclohexane or ethyl acetate (EtOAc) solution could form gel immediately after sonication. However, the stability of the formed gel was poor. It shrunk to release some solvent, and then precipitates appeared after left for over 1 hour. The MCC4 xerogel displayed a three-dimensional sponge-like nanostructure and the precipitates obtained form MCC4 gel showed a honeycomb-like structure. The xerogel of MCC6 and MCC8 gave a regular 3D fibrous network, consisting of entangled bundles of fibers. Dynamic spectroscopic data and theoretical calculation results provided explanations for the possible head to tail molecular aggregation mode, and intermolecularл…лinteractions were the main driving forces for the assembly process. Interestingly, the gel produced from MCC6 is sensitive to shear stress, thermo-, aniline, and formic acid stimulus, giving obviously different aggregation behaviors as well as emissions properties. For there are many effect factors in the actual environments, investigations on the multi-stimuli-responsive functional gel will form a steady foundation for the applications of smart materials.4. In chapter V, we have studied the properties of ultrasound accelerating gelation rates and intermolecular interactions between DUCn gelators.It is interesting to find that the gelators not only form the conventional thermoreversible gels, but also respond to ultrasound irradiation to form the sfimuli-responsive organogels. The environmental factors, such as uttrasound and temperature have great impacts on their aggregation properties. The morphology, DSC, IR and NMR studies suggest that the strong gelator-gelator interactions includingл…лinteractions of QA cores and H-bonding interactions of urea groups are responsible for the formation of gel. The ultrasound irradiation can quickly induce the semistable initial aggregates, which spontaneously propagate to form the well-ordered nanostructures. The UV-Vis, PL spectra and XRD studies support the proposed possible stacking structure with the face-to-face arrangement of chromophores and directional hydrogen-bonded chains. Compared with cholesterol-appended quinacridone derivatives, different molecular structures endow themselves specific packing model and affect photophysical properties.In summary, we have synthesized and characterized functional molecular gels system based on quinacridone derivatives. The mechanism of ultrasound-induced gelation and effects of ultrasound on the gelation were investigated. Novel nano/micro-materials with photoelectric groups were prepared using the xerogel. Molecular packing model was studied and confirmed that intermolecular interactions play important role in the assembly process. The environment factors could impact the photophysical properties. Thus, research on photoelectric molecules based functional molecular gels will achieve its potential applications.