Based on this standpoint, it is desirable that {TAIL ~ the functional chelating agent} 104 has {HEAD ~ a π electron}, which is, however, not always necessary 
Based on this standpoint , it is desirable that { TAIL ~ the functional chelating agent } 104 has { HEAD ~ a π electron } , which is , however , not always necessary
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH