The preparation and characterization of the -oxochlorin derivative [3,3,7,8,12,13,17,18-octaethyl-(3H)-porphin-2-onato(2-)]copper(II), [Cu(oxoOEC)], and its π-cation radical derivative, [Cu(oxoOEC • )][SbCl 6 ], are described. Both compounds have been characterized by single-crystal X-ray structure determinations; IR, UV/vis/near-IR, and EPR spectroscopies; and temperature-dependent magnetic susceptibility measurements. Crystals of [Cu-(oxoOEC)] have two crystallographically distinct molecules, one at a general position ([Cu(oxoOEC)]-gen) and a second at a special position ([Cu(oxoOEC)]-spe). [Cu(oxoOEC)]-gen has a S 4 -saddled conformation whereas [Cu(oxoOEC)]-spe has a modest ruffled conformation. [Cu(oxoOEC • )][SbCl 6 ] shows a cofacial dimeric unit in the solid state, with a mean plane separation of 3.41 Å and a lateral shift of 5.47 Å. Crystal data for [Cu-(oxoOEC)]: monoclinic, space group C2/c, Z ) 12, a ) 38.404(8) Å, b ) 14.692(6) Å, c ) 16.977(11) Å, ) 101.46(2)°. Crystal data for [Cu(oxoOEC • )][SbCl 6 ]: triclinic, space group P1 h, Z ) 2, a ) 13.063(1) Å, b ) 14.108(2) Å, c ) 11.486(2) Å, R ) 93.77(3)°, ) 102.17(1)°, γ ) 74.07(1)°. The EPR spectrum of [Cu-(oxoOEC • )][SbCl 6 ] in frozen dichloromethane at 77 K shows the characteristics of a dimeric copper(II) triplet state. Two broad, concentration-dependent near-IR "dimer bands" appear at 1285 and 1548 nm for [Cu(oxoOEC • )]-[SbCl 6 ]. Solid-state magnetic susceptibility measurements for [Cu(oxoOEC • )][SbCl 6] resulted in a large temperature dependence of the magnetic moments that can best be fit with a four-spin model. This model includes antiferromagnetic intermolecular copper-copper coupling (2J Cu-Cu ) -70 cm -1 ), antiferromagnetic radical-radical coupling (2J r-r ) -139 cm -1 ), and ferromagnetic intramolecular copper-radical coupling (2J Cu-r ) 139 cm -1 ).

The “maker” movement is receiving a lot of attention, especially in the field of education. In this context, we have created an Arduino–carbon dioxide fountain, devised to use digital tools, such as the Arduino microcontroller, a pressure sensor, and code, in combination with a solenoid valve and laboratory equipment to open the valve automatically and demonstrate the carbon dioxide fountain. In a previous work describing a carbon dioxide fountain experiment, students opened the valve if the pressure inside the round-bottom flask was deemed sufficiently low; they then observed the carbon dioxide fountain phenomenon. However, in the Arduino–carbon dioxide fountain experiment, the pressure sensor measures the pressure inside the round-bottom flask and sends the measured pressure value to the microcontroller. The microcontroller signals the solenoid valve to open when the measured pressure value is less than a setting value on the code. This fountain experiment provides students with the opportunity to apply and reinforce their understanding of chemistry concepts using digital tools to code a computer-operated carbon dioxide fountain.

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