We need -lf2c here... we will never depend on g2c.
--- Makefile.in~	Wed Jan 17 12:08:54 2007
+++ Makefile.in	Wed Jan 17 12:39:20 2007
@@ -128,7 +128,7 @@
 LTLIBOBJS = @LTLIBOBJS@
 MAKEINFO = @MAKEINFO@
 MOPAC7_CFLAGS = @MOPAC7_CFLAGS@
-MOPAC7_LIBS = @MOPAC7_LIBS@
+MOPAC7_LIBS = @MOPAC7_LIBS@ -lf2c
 OBJEXT = @OBJEXT@
 PACKAGE = @PACKAGE@
 PACKAGE_BUGREPORT = @PACKAGE_BUGREPORT@

why we need it here again?
--- libghemical.pc.in~	Tue Aug  1 19:46:49 2006
+++ libghemical.pc.in	Wed Jan 17 13:15:00 2007
@@ -6,5 +6,5 @@
 Name: libghemical
 Description: A library that contains molecular modelling functionality.
 Version: @LIBVERSION@
-Libs: -L${libdir} -lghemical @SC_LIBS@ @MOPAC7_LIBS@
+Libs: -L${libdir} -lghemical @SC_LIBS@ @MOPAC7_LIBS@ -lf2c
 Cflags: -I${includedir}/ghemical @SC_CPPFLAGS@ @MOPAC7_CFLAGS@
