A Platinum(II) Terpyridine Metallogel with an L‐Valine‐Modified Alkynyl Ligand: Interplay of Pt⋅⋅⋅Pt, π–π and Hydrogen‐Bonding Interactions

A series of platinum(II) terpyridine complexes with L ‐valine‐modified alkynyl ligands has been synthesized. A complex with an unsubstituted terpyridine and one valine unit on the alkynyl is shown to be capable of gel formation, which is in sharp contrast to the gelation properties of the corresponding organic counterparts. Upon sol–gel transition, a drastic color change from yellow to red is observed, which is indicative of the involvement of Pt ??? Pt interactions. Through the concentration‐ and temperature‐dependent UV/Vis absorption, emission, circular dichroism, and ¹H NMR studies, the contribution of hydrogen bonding, Pt ??? Pt and π–π stacking interactions as driving forces for gelation have been established, and the importance of maintaining a delicate balance between different intermolecular forces has also been illustrated.     

Synthesis and Reactions of 1,4,4a,5,8,8a-Hexahydro-1,4-Methano-5,8-Ethenonaphthalene

The preparation of the titled compound 1 is described. Its photochemical reaction and its formation of a molybdenum carbonyl complex are also reported.     

ARTIFICIAL DISPERSAL OF VOID PATTERNS IN UNIDIRECTIONAL FREEZING

Experiments were conducted to observe the effects of wire screens, wire wool mesh, and soluble gases on the solidification shrinkage void pattern for liquids frozen in constant-volume containers. Prospective applications of these techniques for creating artificial void dispersal are evaluated in light of the models for void initiation and growth developed in an accompanying article. All three approaches show promise of providing better management of solidification shrinkage voids when thermal energy is stored in phase-change materiats, especially under conditions where the voids are ordinarily concentrated to an unacceptable degree. We feel that these results will eventually help usher in a new generation of high-performance thermal energy storage systems due to better void control.     

聚甲基丙烯酸甲酯热氧化降解的化学动力学研究

使用质谱、热分析手段研究了PMMA热解反应.结果表明,在氮气中,PMMA-CH=CH2有两个失重阶段,分别对应于主链末端双键引发的断链和主链无规则断链反应,转折点的失重率约为26%.其中,第一阶段的失重速率受扩散过程控制,平均表观活化能E为158.5 kJ/mol, lnA为27.69;第二失重阶段为1.5级化学反应,平均表观活化能E为214.79 kJ/mol, lnA为40.46.在空气中, PMMA也有两个失重阶段,反应机理为1级化学反应,转折点处的失重率约为70%.其中在第一失重阶段平均表观活化能E为130.32 kJ/mol, lnA为24.81,在此阶段中, 过氧化基团的分解反应对PMMA的失重速率有重要影响; 在空气中第二失重阶段平均表观活化能E为 78.25 kJ/mol, lnA为13.97.     

On the area of constant mean curvature discs and annuli with circular boundaries

It is still an open question whether a constant mean curvature (CMC) disc which is bounded by a circle is necessarily a spherical cap or a flat disc. The authors together with López [1] recently showed that the only stable CMC discs which are bounded by a circle are spherical caps. In this paper we derive lower bounds for the area of constant mean curvature discs and annuli with circular boundaries in 3-dimensional space forms. Received November 8, 1999; in final form January 18, 2000 / Published online March 12, 2001     

Preparation of Hydroquinone‐Containing Polymers by ROMP

Polymers containing ortho‐ and para‐hydroquinone moieties 5a,b and 6a are prepared in good yields by ROMP from hydroquinone‐fused norbornadiene derivatives 1a,b and 2a . Oxidation of 5b yielded a quinone derivative 7 , which is evidenced by a strong absorption at 1656 cm^?1 in infrared spectrum.