Studies On The Synthesis, Crystal Structures And Antitumor Activities Of The Complexes, Schiff Bases And Supermolecules Derived From Nitrogen-Containing Heterocyclic Compounds

Nitrogen-containing heterocyclic compounds have attracted extensive attentiondue to their generally high biological activity, low toxicity, good coordination abilityand versatile structures. Complexes derived from S, N-containing heterocycliccompounds generally demonstrate good bioactivity in particular. In addition, SomeN-containing heterocyclic compounds have some special properties like resonancestructures and tautomerism. Therefore, it is of great significance to study thestructures and bioactivities of N-containing heterocyclic compounds.In this paper,4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one （HPMBP）,2-amino-4-methylpyridine （2-4AP）,2-amino-5-methylpyridine （2-5AP） and2-aminobenzothiazole （2-AB） are selected as the raw materials. Several crystals oftheir complexes, Schiff bases and supermolecules are obtained and characterizedusing a combination of elemental analysis, IR spectrometry, UV-Vis spectrometry andX-ray single crystal diffraction. Fluorescence properties of complexes[Zn（C₇H₆N₂S）₂（CH₃COO）₂] and [Cd（C₇H₆N₂S）₂（CH₃COO）₂] are investigated and theresults show that both of them demonstrate good fluorescence properties. NaturalBond Orbital （NBO） of the complexes, Schiff bases and supermolecules are analyzedand their frontier molecular orbital components are calculated using DensityFunctional Theory （DFT） B3LYP method. Based on the calculation results, theirresonance structures are discussed. Antitumor activity screening of the synthesizedcomplexes and Schiff bases is carried out using MTT method. Then the inhibition and apoptosis induction effect of the Schiff bases derived from HPMBP and2-amino-4-methylphenol to the chymotrypsin-like （CT-like） enzymes and theirWestern blot analysis for several proteasome targets in MDA-MB-231cells arestudied. The details of contents are as follow:（1） One single crystal of K（I） coordination polymer and six single crystals ofSchiff bases are obtained using4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one（HPMBP） as the raw material.The K（I） coordination polymer is characterized using a combination of elementalanalysis, X-ray single crystal diffraction and IR spectrometry. The results show thatthis K（I） coordination polymer has a infinite one-dimensional chain structure.Adjacent chains are connected through the water cluster chains consisting of two freewater molecules and three coordinated water molecules, forming a three dimensionalnetwork. Its fomula is [K_2n(C₁₇H₁₃N₂O₂)_<sub>2n（H₂O）_3n]·_2nH₂O.The six Schiff base is characterized by elemental analysis, X-ray single crystaldiffraction, IR spectrometry and UV-Vis spectrometry. The results show that threecrystals contain methanol molecules and are supermolecules while others do notcontain methanol molecules. The result from X-ray single crystal diffraction indicatesthat the Schiff base has transformed into the amino tautomer from the imino tautomerformed through reaction, and the proton has transferred to the N atom in the C＝Ndouble bond of the Schiff base from the N atom in the pyrazolone ring.Resonance structures of the Schiff bases are analyzed and discussed. The resultssuggest that while all the amino tautomers have resonance structures, they existprimarily as the amino resonance forms.Frontier molecular orbital energies and components of the Schiff bases arecalculated using Density Functional Theory. The results indicate that the six Schiffbases have very similar frontier molecular orbital energies and total molecularenergies. Compared with that of keto HPMBP and enol HPMBP, the total molecularenergies have decreased dramatically and the gaps between HOMO and LUMO haveincreased slightly, indicating the stability of the compounds.（2） Single crystals of novel complexes and supermolecules are obtained using 2-amino-4-methylpyridine （2-4AP）,2-amino-5-methylpyridine （2-5AP） and2-aminobenzothiazole （2-AB） as the raw materials.The complexes and supermolecules are characterized by elemental analysis,X-ray single crystal diffraction and IR spectrometry. The results indicate that the Zn（II）and Cd（II） complexes have the same coordination mode, and they aretetra-coordinated mononuclear complexes. The acetates serve as the bidentate ligandswhile2-aminobenzothiazoles serve as the monodentate ligands. Their structures are[Zn（C₇H₆N₂S）₂（CH₃COO）₂] and [Cd（C₇H₆N₂S）₂（CH₃COO）₂].Resonance structures of the supermolecules and the ligands in the complexes areanalyzed and discussed, indicating that they all have amino-imino resonancestructures. The supermolecules exist primarily in the imino resonance forms while theligands exist primarily in the amino resonance forms. All the supermolecules arenitrate salts. The aromatic N atom has been protonated to form the cation and thepositive charge has transferred to the amine group through resonance, forming theimino nitrate salt. Possible tautomerism route were discussed, and the speculation wasraised that the aromatic N atom protonated anion can serve as the intermedium oftautomerism.Frontier molecular orbital energies and components of the complexes arecalculated using Density Functional Theory, which shows that the complexes arestable. Part of the negative charges has transferred from the acetate ligands to themetal ions and frontier molecular orbital evenly distributes on the2-aminobenzothiazole ligands.Fluorescence properties of complexes [Zn （C₇H₆N₂S）₂（CH₃COO）₂] and [Cd（C₇H₆N₂S）₂（CH₃COO）₂] are investigated, which shows that they exhibit goodfluorescence properties.（3） Antitumor screening of the synthesized complexes and Schiff base are carriedout, which shows that complex [Zn （C₇H₆N₂S）₂（CH₃COO）₂], the Schiff base derivedfrom HPMBP and2-amino-4-methylphenol and the Schiff base derived from HPMBPand3-aminophenol demonstrate good antitumor activities.The Schiff base derived from HPMBP and2-amino-4-methylphenol is further investigated. Studies on the interaction between the Schiff base and Chymotrypsinlike show that the Schiff base demonstrates good inhibition effects to Chymotrypsinlike. In addition, this effect will enhance with the increasement of concentration andinteraction time of Schiff base.Western blot analysis for several proteasome in MDA-MB-231cancer cells ofthe Schiff base in different concentration and by different time was conducted. Theresults show that the Schiff base can induce the accumulation of several proteasometargets in concentration-dependent and time-dependent mode.