diff --git a/avogadro/qtopengl/CMakeLists.txt b/avogadro/qtopengl/CMakeLists.txt
index 8d57100ad0..dc74ef102a 100644
--- a/avogadro/qtopengl/CMakeLists.txt
+++ b/avogadro/qtopengl/CMakeLists.txt
@@ -1,5 +1,5 @@
 if(QT_VERSION EQUAL 6)
-  find_package(Qt6 COMPONENTS  Widgets OpenGLWidgets REQUIRED)
+  find_package(Qt6 REQUIRED COMPONENTS Widgets OpenGLWidgets)
 else()
   find_package(Qt5 COMPONENTS Widgets REQUIRED)
 endif()
@@ -19,7 +19,7 @@ target_sources(QtOpenGL PRIVATE
 )
 
 avogadro_add_library(QtOpenGL)
-target_link_libraries(QtOpenGL Avogadro::Rendering Avogadro::QtGui Qt::Widgets)
+target_link_libraries(QtOpenGL PUBLIC Avogadro::Rendering Avogadro::QtGui Qt::Widgets)
 if(QT_VERSION EQUAL 6)
-  target_link_libraries(QtOpenGL Qt::OpenGLWidgets)
+  target_link_libraries(QtOpenGL PRIVATE Qt6::OpenGLWidgets)
 endif()
diff --git a/avogadro/qtopengl/glwidget.h b/avogadro/qtopengl/glwidget.h
index be600aaba5..c1bb8cf696 100644
--- a/avogadro/qtopengl/glwidget.h
+++ b/avogadro/qtopengl/glwidget.h
@@ -13,7 +13,12 @@
 #include <avogadro/rendering/glrenderer.h>
 
 #include <QPointer>
+
+#if QT_VERSION >= 0x060000
+#include <QtOpenGLWidgets/QOpenGLWidget>
+#else
 #include <QOpenGLWidget>
+#endif
 
 class QTimer;
 
diff --git a/avogadro/qtplugins/aligntool/CMakeLists.txt b/avogadro/qtplugins/aligntool/CMakeLists.txt
index 6b579404d9..d4f9e464e8 100644
--- a/avogadro/qtplugins/aligntool/CMakeLists.txt
+++ b/avogadro/qtplugins/aligntool/CMakeLists.txt
@@ -1,3 +1,9 @@
+if(QT_VERSION EQUAL 6)
+  find_package(Qt6 COMPONENTS Gui REQUIRED)
+else()
+  find_package(Qt5 COMPONENTS Widgets REQUIRED)
+endif()
+
 set(aligntool_srcs
   aligntool.cpp
 )
@@ -20,3 +26,9 @@ avogadro_plugin(AlignTool
 )
 
 target_link_libraries(AlignTool PRIVATE Avogadro::QtOpenGL)
+
+if(QT_VERSION EQUAL 6)
+  target_link_libraries(AlignTool PRIVATE Qt6::Gui)
+else()
+  target_link_libraries(AlignTool PRIVATE Qt5::Widgets)
+endif()
diff --git a/avogadro/qtplugins/coordinateeditor/coordinateeditordialog.cpp b/avogadro/qtplugins/coordinateeditor/coordinateeditordialog.cpp
index f73260d420..7928ce451a 100644
--- a/avogadro/qtplugins/coordinateeditor/coordinateeditordialog.cpp
+++ b/avogadro/qtplugins/coordinateeditor/coordinateeditordialog.cpp
@@ -675,7 +675,7 @@ QString CoordinateEditorDialog::detectInputFormat() const
   FORMAT_DEBUG(qDebug() << "\n\nExamining sample:" << sample;)
 
   // Split the string into tokens, and identify the type of each.
-  QList<QString> tokens(sample.split(TOKEN_SEPARATOR, QString::SkipEmptyParts));
+  QList<QString> tokens(sample.split(TOKEN_SEPARATOR, Qt::SkipEmptyParts));
   QList<TokenType> tokenTypes;
   tokenTypes.reserve(tokens.size());
   size_t tokenTypeCounts[3] = { 0, 0, 0 };
diff --git a/avogadro/qtplugins/forcefield/CMakeLists.txt b/avogadro/qtplugins/forcefield/CMakeLists.txt
index 0ffd8de432..cbd6fb14a6 100644
--- a/avogadro/qtplugins/forcefield/CMakeLists.txt
+++ b/avogadro/qtplugins/forcefield/CMakeLists.txt
@@ -1,3 +1,9 @@
+if(QT_VERSION EQUAL 6)
+  find_package(Qt6 COMPONENTS Gui REQUIRED)
+else()
+  find_package(Qt5 COMPONENTS Widgets REQUIRED)
+endif()
+
 set(forcefield_srcs
   forcefield.cpp
   forcefielddialog.cpp
@@ -28,6 +34,12 @@ avogadro_plugin(Forcefield
 
 target_link_libraries(Forcefield PRIVATE Avogadro::Calc)
 
+if(QT_VERSION EQUAL 6)
+  target_link_libraries(Forcefield PRIVATE Qt6::Gui)
+else()
+  target_link_libraries(Forcefield PRIVATE Qt5::Widgets)
+endif()
+
 if (BUILD_GPL_PLUGINS AND OpenBabel3_LIBRARY)
   target_link_libraries(Forcefield PRIVATE OpenBabel3)
 endif()
diff --git a/avogadro/qtplugins/forcefield/obmmenergy.cpp b/avogadro/qtplugins/forcefield/obmmenergy.cpp
index 594dba9f80..41bae1977f 100644
--- a/avogadro/qtplugins/forcefield/obmmenergy.cpp
+++ b/avogadro/qtplugins/forcefield/obmmenergy.cpp
@@ -224,8 +224,9 @@ Real OBMMEnergy::value(const Eigen::VectorXd& x)
   input = "coord\n";
   for (Index i = 0; i < x.size(); i += 3) {
     // write as x y z (space separated)
-    input += QString::number(x[i]) + " " + QString::number(x[i + 1]) + " " +
-             QString::number(x[i + 2]) + "\n";
+    input += QString::number(x[i]).toUtf8() + " " +
+             QString::number(x[i + 1]).toUtf8() + " " +
+             QString::number(x[i + 2]).toUtf8() + "\n";
   }
 
   result = writeAndRead(input);
@@ -257,8 +258,9 @@ void OBMMEnergy::gradient(const Eigen::VectorXd& x, Eigen::VectorXd& grad)
   QByteArray result, input = "coord\n";
   for (Index i = 0; i < x.size(); i += 3) {
     // write as x y z (space separated)
-    input += QString::number(x[i]) + " " + QString::number(x[i + 1]) + " " +
-             QString::number(x[i + 2]) + "\n";
+    input += QString::number(x[i]).toUtf8() + " " +
+             QString::number(x[i + 1]).toUtf8() + " " +
+             QString::number(x[i + 2]).toUtf8() + "\n";
   }
 
   result = writeAndRead(input);
diff --git a/avogadro/qtplugins/forcefield/scriptenergy.cpp b/avogadro/qtplugins/forcefield/scriptenergy.cpp
index f7bc5c7e9f..6d9925caf3 100644
--- a/avogadro/qtplugins/forcefield/scriptenergy.cpp
+++ b/avogadro/qtplugins/forcefield/scriptenergy.cpp
@@ -19,6 +19,8 @@
 #include <QtCore/QDir>
 #include <QtCore/QScopedPointer>
 
+#include <QRegularExpression>
+
 #include <qjsonarray.h>
 #include <qjsondocument.h>
 #include <qjsonobject.h>
@@ -115,8 +117,9 @@ Real ScriptEnergy::value(const Eigen::VectorXd& x)
   QByteArray input;
   for (Index i = 0; i < x.size(); i += 3) {
     // write as x y z (space separated)
-    input += QString::number(x[i]) + " " + QString::number(x[i + 1]) + " " +
-             QString::number(x[i + 2]) + "\n";
+    input += QString::number(x[i]).toUtf8() + " " +
+             QString::number(x[i + 1]).toUtf8() + " " +
+             QString::number(x[i + 2]).toUtf8() + "\n";
   }
   QByteArray result = m_interpreter->asyncWriteAndResponse(input);
 
@@ -125,7 +128,7 @@ Real ScriptEnergy::value(const Eigen::VectorXd& x)
   double energy = 0.0;
   for (auto line : lines) {
     if (line.startsWith("AvogadroEnergy:")) {
-      QStringList items = line.split(" ", QString::SkipEmptyParts);
+      QStringList items = line.split(" ", Qt::SkipEmptyParts);
       if (items.size() > 1) {
         energy = items[1].toDouble();
         break;
@@ -148,8 +151,9 @@ void ScriptEnergy::gradient(const Eigen::VectorXd& x, Eigen::VectorXd& grad)
   QByteArray input;
   for (Index i = 0; i < x.size(); i += 3) {
     // write as x y z (space separated)
-    input += QString::number(x[i]) + " " + QString::number(x[i + 1]) + " " +
-             QString::number(x[i + 2]) + "\n";
+    input += QString::number(x[i]).toUtf8() + " " +
+             QString::number(x[i + 1]).toUtf8() + " " +
+             QString::number(x[i + 2]).toUtf8() + "\n";
   }
   QByteArray result = m_interpreter->asyncWriteAndResponse(input);
 
@@ -165,7 +169,7 @@ void ScriptEnergy::gradient(const Eigen::VectorXd& x, Eigen::VectorXd& grad)
     }
 
     if (readingGrad) {
-      QStringList items = line.split(" ", QString::SkipEmptyParts);
+      QStringList items = line.split(" ", Qt::SkipEmptyParts);
       if (items.size() == 3) {
         grad[i] = items[0].toDouble();
         grad[i + 1] = items[1].toDouble();
@@ -365,7 +369,8 @@ void ScriptEnergy::processElementString(const QString& str)
   QString str2(str);
   str2.replace(',', ' ');
   // then split on whitespace
-  QStringList strList = str2.split(QRegExp("\\s+"), QString::SkipEmptyParts);
+  QStringList strList =
+    str2.split(QRegularExpression("\\s+"), Qt::SkipEmptyParts);
   foreach (QString sstr, strList) {
     // these should be numbers or ranges (e.g., 1-84)
     if (sstr.contains('-')) {
diff --git a/avogadro/qtplugins/label/CMakeLists.txt b/avogadro/qtplugins/label/CMakeLists.txt
index 8b666cbc51..97bd0cdf7a 100644
--- a/avogadro/qtplugins/label/CMakeLists.txt
+++ b/avogadro/qtplugins/label/CMakeLists.txt
@@ -25,4 +25,12 @@ avogadro_plugin(LabelEditor
 )
 
 target_link_libraries(Label LINK_PRIVATE Avogadro::Rendering)
-target_link_libraries(LabelEditor LINK_PRIVATE Avogadro::QtOpenGL)
\ No newline at end of file
+target_link_libraries(LabelEditor
+  LINK_PRIVATE
+    Avogadro::Rendering
+    Avogadro::QtOpenGL)
+
+target_include_directories(LabelEditor
+  PRIVATE
+    ${CMAKE_CURRENT_BINARY_DIR}/../../rendering
+    ${CMAKE_CURRENT_BINARY_DIR}/../../qtopengl)
diff --git a/avogadro/qtplugins/playertool/CMakeLists.txt b/avogadro/qtplugins/playertool/CMakeLists.txt
index f0df58510e..a9c5cccb26 100644
--- a/avogadro/qtplugins/playertool/CMakeLists.txt
+++ b/avogadro/qtplugins/playertool/CMakeLists.txt
@@ -1,3 +1,10 @@
+if(QT_VERSION EQUAL 6)
+  find_package(Qt6
+    REQUIRED COMPONENTS
+      OpenGL
+      OpenGLWidgets)
+endif()
+
 avogadro_plugin(PlayerTool
   "Player tool"
   ToolPlugin
@@ -13,3 +20,10 @@ target_link_libraries(PlayerTool
     gwavi
     gif-h
     Avogadro::QtOpenGL)
+
+if(QT_VERSION EQUAL 6)
+  target_link_libraries(PlayerTool
+    PRIVATE
+      Qt6::OpenGL
+      Qt6::OpenGLWidgets)
+endif()
diff --git a/avogadro/qtplugins/qtaim/qtaimwavefunction.cpp b/avogadro/qtplugins/qtaim/qtaimwavefunction.cpp
index 76350805a3..8500f71c13 100644
--- a/avogadro/qtplugins/qtaim/qtaimwavefunction.cpp
+++ b/avogadro/qtplugins/qtaim/qtaimwavefunction.cpp
@@ -134,7 +134,7 @@ bool QTAIMWavefunction::initializeWithWFNFile(const QString& fileName)
 
   while (fileContentsByLine.first().startsWith("TYPE ASSIGNMENTS")) {
     QString line(fileContentsByLine.first().mid(20, -1));
-    QStringList splitLine(line.split(" ", QString::SkipEmptyParts));
+    QStringList splitLine(line.split(" ", Qt::SkipEmptyParts));
 
     for (qint64 i = 0; i < splitLine.length(); ++i) {
       typeAssignmentsList.append(splitLine.at(i).toLongLong());
@@ -261,7 +261,7 @@ bool QTAIMWavefunction::initializeWithWFNFile(const QString& fileName)
 
   while (fileContentsByLine.first().startsWith("EXPONENTS")) {
     QString line(fileContentsByLine.first().mid(9, -1));
-    QStringList splitLine(line.split(" ", QString::SkipEmptyParts));
+    QStringList splitLine(line.split(" ", Qt::SkipEmptyParts));
 
     for (qint64 i = 0; i < splitLine.length(); ++i) {
       QString str(splitLine.at(i));
@@ -324,7 +324,7 @@ bool QTAIMWavefunction::initializeWithWFNFile(const QString& fileName)
     m_molecularOrbitalEigenvalues[i] = molecularOrbitalEigenvaluesList.at(i);
 
   moCoefficientsStringList =
-    moCoefficientsStringList.join(" ").split(" ", QString::SkipEmptyParts);
+    moCoefficientsStringList.join(" ").split(" ", Qt::SkipEmptyParts);
 
   for (qint64 i = 0; i < moCoefficientsStringList.length(); ++i) {
     QString str(moCoefficientsStringList.at(i));
diff --git a/avogadro/qtplugins/resetview/CMakeLists.txt b/avogadro/qtplugins/resetview/CMakeLists.txt
index 9da8631992..ab6a89d264 100644
--- a/avogadro/qtplugins/resetview/CMakeLists.txt
+++ b/avogadro/qtplugins/resetview/CMakeLists.txt
@@ -1,3 +1,7 @@
+if(QT_VERSION EQUAL 6)
+  find_package(Qt6 REQUIRED COMPONENTS OpenGLWidgets)
+endif()
+
 avogadro_plugin(ResetView
   "Manipulate the view camera."
   ExtensionPlugin
@@ -8,3 +12,9 @@ avogadro_plugin(ResetView
 )
 
 target_link_libraries(ResetView PRIVATE Avogadro::QtOpenGL)
+
+if(QT_VERSION EQUAL 6)
+  target_link_libraries(ResetView
+    PRIVATE
+      Qt6::OpenGLWidgets)
+endif()
diff --git a/avogadro/qtplugins/scriptcharges/scriptchargemodel.cpp b/avogadro/qtplugins/scriptcharges/scriptchargemodel.cpp
index 5fa58a1a6c..831fe24fe5 100644
--- a/avogadro/qtplugins/scriptcharges/scriptchargemodel.cpp
+++ b/avogadro/qtplugins/scriptcharges/scriptchargemodel.cpp
@@ -357,7 +357,7 @@ void ScriptChargeModel::processElementString(const QString& str)
   QString str2(str);
   str2.replace(',', ' ');
   // then split on whitespace
-  QStringList strList = str2.split(QRegExp("\\s+"), QString::SkipEmptyParts);
+  QStringList strList = str2.split(QRegExp("\\s+"), Qt::SkipEmptyParts);
   foreach (QString sstr, strList) {
     // these should be numbers or ranges (e.g., 1-84)
     if (sstr.contains('-')) {
diff --git a/avogadro/qtplugins/surfaces/CMakeLists.txt b/avogadro/qtplugins/surfaces/CMakeLists.txt
index b4235c97ab..256a65e45d 100644
--- a/avogadro/qtplugins/surfaces/CMakeLists.txt
+++ b/avogadro/qtplugins/surfaces/CMakeLists.txt
@@ -1,3 +1,7 @@
+if(QT_VERSION EQUAL 6)
+  find_package(Qt6 REQUIRED COMPONENTS OpenGL)
+endif()
+
 set(surfaces_srcs
   gaussiansetconcurrent.cpp
   slatersetconcurrent.cpp
@@ -23,3 +27,9 @@ target_link_libraries(Surfaces
     gif-h
     gwavi
     tinycolormap)
+
+if(QT_VERSION EQUAL 6)
+  target_link_libraries(Surfaces
+    PRIVATE
+      Qt6::OpenGL)
+endif()
diff --git a/avogadro/quantumio/gamessukout.cpp b/avogadro/quantumio/gamessukout.cpp
index dcb6b1d098..c49eb4e95a 100644
--- a/avogadro/quantumio/gamessukout.cpp
+++ b/avogadro/quantumio/gamessukout.cpp
@@ -43,7 +43,7 @@ bool tokenize(std::vector<std::string>& vcr, const char* buf,
   splitString += QString(delimstr);
   splitString += QString("]");
   QRegExp splitter(splitString);
-  foreach (const QString& str, tmp.split(splitter, QString::SkipEmptyParts))
+  foreach (const QString& str, tmp.split(splitter, Qt::SkipEmptyParts))
     vcr.push_back(str.toStdString());
 
   return true;