Macrocyclization long range

X-Ray structure shows that Pd is coordinated to four S 55 atoms in a square planar fashion only long range weak axial interactions are observed with the two remaining S atoms, i.e. the conformation of the macrocycle is an S-shaped double boat, with the Pd11 ion at the molecular inversion centre... 

Although Pcs are macrocycles that have a strong tendency to aggregate into columnar stacks by tt-tt stacking interaction, the formation of long-range, ordered aggregates based on these systems has been seldom reported [84,117]. 

Synthesis and characterization of lithocholic acid derived dipyrromethanes. Koivukorpi et aO in early 2004 reported the synthesis of a series of steroidal dipyrromethane analogues that can be exploited for the synthesis of pyrrole-steroidal macrocycles. The authors used long-range HMBC data to confirm the structure. 

Two general procedures have been used to obtain AH values. The first involves the measurement of log K values over a range of temperatures the observed variation may be used to derive the required AH value. However, because of the usual errors inherent in log K determinations coupled with the limited temperature range normally possible, AH values obtained in this manner tend to be somewhat unreliable. In contrast, the direct determination of AH using calorimetry commonly results in values which are considerably more accurate. Nevertheless, such calorimetric determinations may still not be easy for particular macrocyclic systems. Difficulties can arise in measuring the total heat evolved for metal complexation when long equilibration times are necessary. To lessen such problems, sensitive calorimeters have been used which are able to integrate the heat released over an extended time. 

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