The polymerase chain reaction (PCR) is a common technique used in high school and undergraduate science teaching. Students often do not fully comprehend the underlying principles of the technique and how optimization of the protocol affects the outcome and analysis. In this molecular biology laboratory, students learn the steps of PCR with an emphasis on primer composition and annealing temperature, which they manipulate to test the effect on successful DNA amplification. Students design experiments to test their hypotheses, promoting a discovery-based approach to laboratory teaching and development of critical-thinking and reasoning skills.
Divalent copper coordination polymers containing an isophthalate ligand and a dipyridylamide ligand show different dimensionalities and topologies depending on pyridyl nitrogen donor disposition and the steric bulk of the substituent on the dicarboxylate aromatic ring. According to single‐crystal X‐ray diffraction, [Cu(ip)(3‐pna)]n (1, ip = isophthalate, 3‐pna = 3‐pyridylnicotinamide) shows a (4, 4) layered grid structure based on {Cu2(OCO)2} dimeric units. {[Cu(ip)(3‐pina)]·H2O}n (2, 3‐pina = 3‐pyridylisonicotinamide) exhibits similar dimeric units, but in contrast to 1 these are connected into a non‐interpenetrated 3D 658 cds network. Both [Cu(mip)(3‐pina)]n (3, mip = 5‐methylisophthalate) and [Cu(meoip)(3‐pina)]n (4, mip = 5‐methoxyisophthalate) display dimer‐based 41263 pcu networks in contrast to 2. Use of 5‐hydroxyisophthalate (H2hip) as a precursor afforded a mixture of {[Cu2(hip)2(3‐pina)4]·9.5H2O}n (5) and [Cu(hip)(3‐pina)]n (6). Compound 5 shows a 2D interdigitated structure with [Cu(hip)]n coordination polymer layers featuring {Cu2(OCO)2} dimeric units and pendant 3‐pina ligands, while 6 also showed a dimer‐based 41263 pcu network. Use of the very sterically bulky 5‐tert‐butylisophthalate (tbip) ligand afforded the 1D chain coordination polymer {[Cu(tbip)(3‐pina)2(H2O)]·H2O}n (7), which contains isolated copper ions in contrast to 1–6, and has a curious “butterfly“ resemblance. Very weak antiferromagnetic coupling is seen within the {Cu2(OCO)2} dimeric units in 1. Thermal decomposition behavior is also discussed.
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