Nitrogen connectors

Fig. 7 Representative molecular wires with nitrogen connectors...

It is essential that a U-tube containing mercury is connected by a T-connector to the nitrogen inlet. The U-tube serves to monitor the pressure on the system and acts as a safety valve in the event of a plugged trap. A slight positive pressure is maintained. 

When the reservoir (with a one-hole connector) was filled with water, salts were added and the compounds were spiked. The pH was adjusted with 1 N HC1 to 7.0. The reservoir was capped and swirled for a few seconds. The upper and lower stopcocks were opened and pressure was applied by using high-pressure, ultrapure, nitrogen gas. The flow rate was controlled by the nitrogen cylinder pressure and by using the fine adjustment on the resin column stopcock. Two flow rates were studied and are described during the presentation of results. The initial flow rate used was 120-150 bed volumes/h (20-25 mL/min). A lower flow rate of approximately 48 bed volumes/h was studied after breakthrough of quinaldic acid was observed. 

In order to construct a three-dimensional bimetallic network based on an [M(CN)6]3- building block, the second metal complex as the connector must have at least three vacant sites for accepting cyanide nitrogens from adjacent [M(CN)6]3-4-ions. These structural requirements are satisfied for the following compounds ... 

Schematic diagrams of the apparatus, designed in our lab at< y, are shown in Fig. 1. Polymer flakes are placed, with a balls of about 5 mm dieter, in a glass an oule A about 4 cm in diameter and 7 cm in length. To the other end of the ampoule an ESR sample tube B is attached. Through connector C, the ampoule can be connected to a vacuum system and then evacuated to 10 mm Hg. After evacuation the connector is sealed off and the ampoule is removed from the vacuum system. The evacuated ampoule is now placed on a vibrator, wWch moves vertically at about 4 cycle per second. The procedure can be carried out in a Dewar flask containing coolant, such as liquid nitrogen, to fix the temperature. After some hours of this vibration, the crushed flakes are transferred to the ESR sample tube without raising the temperature of the sample. Ihen, sample tube containing the fractured flakes is placed in an ESR cavity at controlled temperature. The ball-mill apparatus permitted polymeric materials to be crushed in vacuum at low temperature and the ESR spectrum to be observed without contamination of oxygen.

Clearly, deuterated molecules are expensive and not always a viable option for economic reasons. X-ray photoelectron spectroscopy (XPS) can be an alternative when a heavier atom such as nitrogen or oxygen is present on the connector chains (but not on the polymer on at least one side of the interface). XPS has a... 

For purging operations, use nitrogen cylinders. These have a CGA 580 valve and fit a CGA 580 nipple and nut connector on the regulator. 

Obtain two nitrogen atoms and three connectors from the molecular model kit, and assemble one nitrogen (N2) molecule. Observe that your model represents a triple-bonded diatomic nitrogen molecule. 

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