An efficient method for the preparation of poly(p-phenyleneethynylene)s (PPEs) from direct coupling reactions between aryl diiodides and inexpensive chemical feedstock calcium carbide is developed.

Novel constrained Schiff-base ligands (inden) were developed based on the well-known salen ligands. Chromium complexes supported by the constrained inden ligands were successfully synthesized and used as catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO 2 ). The catalyst having tert-butyl ( t Bu) groups as substituents in combination with tetrabutylammonium bromide (TBAB) as a cocatalyst exhibited very high catalytic activity with a turnover frequency of up to 14800 h −1 for the conversion of CO 2 and propylene oxide into propylene carbonate exclusively at 100 °C and 300 psi of CO 2 under solvent-free conditions. The catalyst was found to be highly active for various epoxide substrates to produce terminal cyclic carbonates in 100% selectivity.

A new turn on fluorescent probe for ferric ion based on poly(m-phenyleneethynylene salicylaldimine) (PPE-IM) has been developed. The preparation of PPE-IM involves postpolymerization functionalization of the corresponding polymeric amine, PPE-AM, via the condensation with salicylaldehyde. The degree of polymerization of both PPE-IM and PPE-IM is 17 with polydispersity index of 1.5. In aqueous solution, the polymeric PPE-IM is highly stable unlike its small molecule analog which is gradually hydrolyzed. The weak fluorescence of initial PPE-IM (k em 5 470) is greatly enhanced by 300 folds upon the addition of Fe 31 . The 1 H NMR reveals that the fluorescence enhancement is caused by Fe 31 -induced hydrolysis of the imine group. The sensing system shows a detection limit of 0.14 lM of Fe 31 .

Metal catalyst contamination is a major concern in the preparation of polymeric materials. For conjugate polymers, trace amount of metal catalyst is detrimental to the optoelectronic properties. In this work, a method for synthesizing highly pure fluorescent polymers, poly(aryleneethynylene)s (PAEs), was developed using heterogeneous Pd/CaCO 3 catalytic system. Polymerization between a variety of aryl diethynes and aryl diiodides or dibromides were achieved using a catalytic amount of Pd/CaCO 3 , CuI, and PPh 3 at 80 C in good to excellent yields (79-100%). Resulting polymers possess degree of polymerization ranging from 8 to 50 with polydispersity index of 1.5-3.6. Importantly, PAEs from Pd/CaCO 3 catalytic system contain considerably lower level of Pd and Cu contamination (1.9 and 3.4 ppm, respectively) than those obtained from classical homogeneous catalyst, Pd(PPh 3 ) 4 and PdCl 2 (PPh 3 ) 2 or heterogeneous catalyst Pd/C. Additional supporting information may be found in the online version of this article.